1------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3------------------------------------------------------------------------------ 4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 5 Bodo Bauer <bb@ricochet.net> 6 72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 9------------------------------------------------------------------------------ 10Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12------------------------------------------------------------------------------ 13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 14 15Table of Contents 16----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 37 score 38 3.2 /proc/<pid>/oom_score - Display current oom-killer score 39 3.3 /proc/<pid>/io - Display the IO accounting fields 40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 41 3.5 /proc/<pid>/mountinfo - Information about mounts 42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 43 3.7 /proc/<pid>/task/<tid>/children - Information about task children 44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 45 3.9 /proc/<pid>/map_files - Information about memory mapped files 46 47 4 Configuring procfs 48 4.1 Mount options 49 50------------------------------------------------------------------------------ 51Preface 52------------------------------------------------------------------------------ 53 540.1 Introduction/Credits 55------------------------ 56 57This documentation is part of a soon (or so we hope) to be released book on 58the SuSE Linux distribution. As there is no complete documentation for the 59/proc file system and we've used many freely available sources to write these 60chapters, it seems only fair to give the work back to the Linux community. 61This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 62afraid it's still far from complete, but we hope it will be useful. As far as 63we know, it is the first 'all-in-one' document about the /proc file system. It 64is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 65SPARC, AXP, etc., features, you probably won't find what you are looking for. 66It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 67additions and patches are welcome and will be added to this document if you 68mail them to Bodo. 69 70We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 71other people for help compiling this documentation. We'd also like to extend a 72special thank you to Andi Kleen for documentation, which we relied on heavily 73to create this document, as well as the additional information he provided. 74Thanks to everybody else who contributed source or docs to the Linux kernel 75and helped create a great piece of software... :) 76 77If you have any comments, corrections or additions, please don't hesitate to 78contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 79document. 80 81The latest version of this document is available online at 82http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 83 84If the above direction does not works for you, you could try the kernel 85mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 86comandante@zaralinux.com. 87 880.2 Legal Stuff 89--------------- 90 91We don't guarantee the correctness of this document, and if you come to us 92complaining about how you screwed up your system because of incorrect 93documentation, we won't feel responsible... 94 95------------------------------------------------------------------------------ 96CHAPTER 1: COLLECTING SYSTEM INFORMATION 97------------------------------------------------------------------------------ 98 99------------------------------------------------------------------------------ 100In This Chapter 101------------------------------------------------------------------------------ 102* Investigating the properties of the pseudo file system /proc and its 103 ability to provide information on the running Linux system 104* Examining /proc's structure 105* Uncovering various information about the kernel and the processes running 106 on the system 107------------------------------------------------------------------------------ 108 109 110The proc file system acts as an interface to internal data structures in the 111kernel. It can be used to obtain information about the system and to change 112certain kernel parameters at runtime (sysctl). 113 114First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 115show you how you can use /proc/sys to change settings. 116 1171.1 Process-Specific Subdirectories 118----------------------------------- 119 120The directory /proc contains (among other things) one subdirectory for each 121process running on the system, which is named after the process ID (PID). 122 123The link self points to the process reading the file system. Each process 124subdirectory has the entries listed in Table 1-1. 125 126 127Table 1-1: Process specific entries in /proc 128.............................................................................. 129 File Content 130 clear_refs Clears page referenced bits shown in smaps output 131 cmdline Command line arguments 132 cpu Current and last cpu in which it was executed (2.4)(smp) 133 cwd Link to the current working directory 134 environ Values of environment variables 135 exe Link to the executable of this process 136 fd Directory, which contains all file descriptors 137 maps Memory maps to executables and library files (2.4) 138 mem Memory held by this process 139 root Link to the root directory of this process 140 stat Process status 141 statm Process memory status information 142 status Process status in human readable form 143 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function 144 symbol the task is blocked in - or "0" if not blocked. 145 pagemap Page table 146 stack Report full stack trace, enable via CONFIG_STACKTRACE 147 smaps a extension based on maps, showing the memory consumption of 148 each mapping and flags associated with it 149 numa_maps an extension based on maps, showing the memory locality and 150 binding policy as well as mem usage (in pages) of each mapping. 151.............................................................................. 152 153For example, to get the status information of a process, all you have to do is 154read the file /proc/PID/status: 155 156 >cat /proc/self/status 157 Name: cat 158 State: R (running) 159 Tgid: 5452 160 Pid: 5452 161 PPid: 743 162 TracerPid: 0 (2.4) 163 Uid: 501 501 501 501 164 Gid: 100 100 100 100 165 FDSize: 256 166 Groups: 100 14 16 167 VmPeak: 5004 kB 168 VmSize: 5004 kB 169 VmLck: 0 kB 170 VmHWM: 476 kB 171 VmRSS: 476 kB 172 VmData: 156 kB 173 VmStk: 88 kB 174 VmExe: 68 kB 175 VmLib: 1412 kB 176 VmPTE: 20 kb 177 VmSwap: 0 kB 178 Threads: 1 179 SigQ: 0/28578 180 SigPnd: 0000000000000000 181 ShdPnd: 0000000000000000 182 SigBlk: 0000000000000000 183 SigIgn: 0000000000000000 184 SigCgt: 0000000000000000 185 CapInh: 00000000fffffeff 186 CapPrm: 0000000000000000 187 CapEff: 0000000000000000 188 CapBnd: ffffffffffffffff 189 Seccomp: 0 190 voluntary_ctxt_switches: 0 191 nonvoluntary_ctxt_switches: 1 192 193This shows you nearly the same information you would get if you viewed it with 194the ps command. In fact, ps uses the proc file system to obtain its 195information. But you get a more detailed view of the process by reading the 196file /proc/PID/status. It fields are described in table 1-2. 197 198The statm file contains more detailed information about the process 199memory usage. Its seven fields are explained in Table 1-3. The stat file 200contains details information about the process itself. Its fields are 201explained in Table 1-4. 202 203(for SMP CONFIG users) 204For making accounting scalable, RSS related information are handled in an 205asynchronous manner and the value may not be very precise. To see a precise 206snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 207It's slow but very precise. 208 209Table 1-2: Contents of the status files (as of 3.20.0) 210.............................................................................. 211 Field Content 212 Name filename of the executable 213 State state (R is running, S is sleeping, D is sleeping 214 in an uninterruptible wait, Z is zombie, 215 T is traced or stopped) 216 Tgid thread group ID 217 Ngid NUMA group ID (0 if none) 218 Pid process id 219 PPid process id of the parent process 220 TracerPid PID of process tracing this process (0 if not) 221 Uid Real, effective, saved set, and file system UIDs 222 Gid Real, effective, saved set, and file system GIDs 223 FDSize number of file descriptor slots currently allocated 224 Groups supplementary group list 225 NStgid descendant namespace thread group ID hierarchy 226 NSpid descendant namespace process ID hierarchy 227 NSpgid descendant namespace process group ID hierarchy 228 NSsid descendant namespace session ID hierarchy 229 VmPeak peak virtual memory size 230 VmSize total program size 231 VmLck locked memory size 232 VmHWM peak resident set size ("high water mark") 233 VmRSS size of memory portions 234 VmData size of data, stack, and text segments 235 VmStk size of data, stack, and text segments 236 VmExe size of text segment 237 VmLib size of shared library code 238 VmPTE size of page table entries 239 VmSwap size of swap usage (the number of referred swapents) 240 Threads number of threads 241 SigQ number of signals queued/max. number for queue 242 SigPnd bitmap of pending signals for the thread 243 ShdPnd bitmap of shared pending signals for the process 244 SigBlk bitmap of blocked signals 245 SigIgn bitmap of ignored signals 246 SigCgt bitmap of caught signals 247 CapInh bitmap of inheritable capabilities 248 CapPrm bitmap of permitted capabilities 249 CapEff bitmap of effective capabilities 250 CapBnd bitmap of capabilities bounding set 251 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 252 Cpus_allowed mask of CPUs on which this process may run 253 Cpus_allowed_list Same as previous, but in "list format" 254 Mems_allowed mask of memory nodes allowed to this process 255 Mems_allowed_list Same as previous, but in "list format" 256 voluntary_ctxt_switches number of voluntary context switches 257 nonvoluntary_ctxt_switches number of non voluntary context switches 258.............................................................................. 259 260Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 261.............................................................................. 262 Field Content 263 size total program size (pages) (same as VmSize in status) 264 resident size of memory portions (pages) (same as VmRSS in status) 265 shared number of pages that are shared (i.e. backed by a file) 266 trs number of pages that are 'code' (not including libs; broken, 267 includes data segment) 268 lrs number of pages of library (always 0 on 2.6) 269 drs number of pages of data/stack (including libs; broken, 270 includes library text) 271 dt number of dirty pages (always 0 on 2.6) 272.............................................................................. 273 274 275Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 276.............................................................................. 277 Field Content 278 pid process id 279 tcomm filename of the executable 280 state state (R is running, S is sleeping, D is sleeping in an 281 uninterruptible wait, Z is zombie, T is traced or stopped) 282 ppid process id of the parent process 283 pgrp pgrp of the process 284 sid session id 285 tty_nr tty the process uses 286 tty_pgrp pgrp of the tty 287 flags task flags 288 min_flt number of minor faults 289 cmin_flt number of minor faults with child's 290 maj_flt number of major faults 291 cmaj_flt number of major faults with child's 292 utime user mode jiffies 293 stime kernel mode jiffies 294 cutime user mode jiffies with child's 295 cstime kernel mode jiffies with child's 296 priority priority level 297 nice nice level 298 num_threads number of threads 299 it_real_value (obsolete, always 0) 300 start_time time the process started after system boot 301 vsize virtual memory size 302 rss resident set memory size 303 rsslim current limit in bytes on the rss 304 start_code address above which program text can run 305 end_code address below which program text can run 306 start_stack address of the start of the main process stack 307 esp current value of ESP 308 eip current value of EIP 309 pending bitmap of pending signals 310 blocked bitmap of blocked signals 311 sigign bitmap of ignored signals 312 sigcatch bitmap of caught signals 313 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead) 314 0 (place holder) 315 0 (place holder) 316 exit_signal signal to send to parent thread on exit 317 task_cpu which CPU the task is scheduled on 318 rt_priority realtime priority 319 policy scheduling policy (man sched_setscheduler) 320 blkio_ticks time spent waiting for block IO 321 gtime guest time of the task in jiffies 322 cgtime guest time of the task children in jiffies 323 start_data address above which program data+bss is placed 324 end_data address below which program data+bss is placed 325 start_brk address above which program heap can be expanded with brk() 326 arg_start address above which program command line is placed 327 arg_end address below which program command line is placed 328 env_start address above which program environment is placed 329 env_end address below which program environment is placed 330 exit_code the thread's exit_code in the form reported by the waitpid system call 331.............................................................................. 332 333The /proc/PID/maps file containing the currently mapped memory regions and 334their access permissions. 335 336The format is: 337 338address perms offset dev inode pathname 339 34008048000-08049000 r-xp 00000000 03:00 8312 /opt/test 34108049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3420804a000-0806b000 rw-p 00000000 00:00 0 [heap] 343a7cb1000-a7cb2000 ---p 00000000 00:00 0 344a7cb2000-a7eb2000 rw-p 00000000 00:00 0 345a7eb2000-a7eb3000 ---p 00000000 00:00 0 346a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001] 347a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 348a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 349a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 350a800b000-a800e000 rw-p 00000000 00:00 0 351a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 352a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 353a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 354a8024000-a8027000 rw-p 00000000 00:00 0 355a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 356a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 357a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 358aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 359ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 360 361where "address" is the address space in the process that it occupies, "perms" 362is a set of permissions: 363 364 r = read 365 w = write 366 x = execute 367 s = shared 368 p = private (copy on write) 369 370"offset" is the offset into the mapping, "dev" is the device (major:minor), and 371"inode" is the inode on that device. 0 indicates that no inode is associated 372with the memory region, as the case would be with BSS (uninitialized data). 373The "pathname" shows the name associated file for this mapping. If the mapping 374is not associated with a file: 375 376 [heap] = the heap of the program 377 [stack] = the stack of the main process 378 [stack:1001] = the stack of the thread with tid 1001 379 [vdso] = the "virtual dynamic shared object", 380 the kernel system call handler 381 382 or if empty, the mapping is anonymous. 383 384The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint 385of the individual tasks of a process. In this file you will see a mapping marked 386as [stack] if that task sees it as a stack. This is a key difference from the 387content of /proc/PID/maps, where you will see all mappings that are being used 388as stack by all of those tasks. Hence, for the example above, the task-level 389map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this: 390 39108048000-08049000 r-xp 00000000 03:00 8312 /opt/test 39208049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3930804a000-0806b000 rw-p 00000000 00:00 0 [heap] 394a7cb1000-a7cb2000 ---p 00000000 00:00 0 395a7cb2000-a7eb2000 rw-p 00000000 00:00 0 396a7eb2000-a7eb3000 ---p 00000000 00:00 0 397a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack] 398a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 399a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 400a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 401a800b000-a800e000 rw-p 00000000 00:00 0 402a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 403a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 404a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 405a8024000-a8027000 rw-p 00000000 00:00 0 406a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 407a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 408a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 409aff35000-aff4a000 rw-p 00000000 00:00 0 410ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 411 412The /proc/PID/smaps is an extension based on maps, showing the memory 413consumption for each of the process's mappings. For each of mappings there 414is a series of lines such as the following: 415 41608048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 417Size: 1084 kB 418Rss: 892 kB 419Pss: 374 kB 420Shared_Clean: 892 kB 421Shared_Dirty: 0 kB 422Private_Clean: 0 kB 423Private_Dirty: 0 kB 424Referenced: 892 kB 425Anonymous: 0 kB 426Swap: 0 kB 427KernelPageSize: 4 kB 428MMUPageSize: 4 kB 429Locked: 374 kB 430VmFlags: rd ex mr mw me de 431 432the first of these lines shows the same information as is displayed for the 433mapping in /proc/PID/maps. The remaining lines show the size of the mapping 434(size), the amount of the mapping that is currently resident in RAM (RSS), the 435process' proportional share of this mapping (PSS), the number of clean and 436dirty private pages in the mapping. Note that even a page which is part of a 437MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used 438by only one process, is accounted as private and not as shared. "Referenced" 439indicates the amount of memory currently marked as referenced or accessed. 440"Anonymous" shows the amount of memory that does not belong to any file. Even 441a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 442and a page is modified, the file page is replaced by a private anonymous copy. 443"Swap" shows how much would-be-anonymous memory is also used, but out on 444swap. 445 446"VmFlags" field deserves a separate description. This member represents the kernel 447flags associated with the particular virtual memory area in two letter encoded 448manner. The codes are the following: 449 rd - readable 450 wr - writeable 451 ex - executable 452 sh - shared 453 mr - may read 454 mw - may write 455 me - may execute 456 ms - may share 457 gd - stack segment growns down 458 pf - pure PFN range 459 dw - disabled write to the mapped file 460 lo - pages are locked in memory 461 io - memory mapped I/O area 462 sr - sequential read advise provided 463 rr - random read advise provided 464 dc - do not copy area on fork 465 de - do not expand area on remapping 466 ac - area is accountable 467 nr - swap space is not reserved for the area 468 ht - area uses huge tlb pages 469 nl - non-linear mapping 470 ar - architecture specific flag 471 dd - do not include area into core dump 472 sd - soft-dirty flag 473 mm - mixed map area 474 hg - huge page advise flag 475 nh - no-huge page advise flag 476 mg - mergable advise flag 477 478Note that there is no guarantee that every flag and associated mnemonic will 479be present in all further kernel releases. Things get changed, the flags may 480be vanished or the reverse -- new added. 481 482This file is only present if the CONFIG_MMU kernel configuration option is 483enabled. 484 485The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 486bits on both physical and virtual pages associated with a process, and the 487soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details). 488To clear the bits for all the pages associated with the process 489 > echo 1 > /proc/PID/clear_refs 490 491To clear the bits for the anonymous pages associated with the process 492 > echo 2 > /proc/PID/clear_refs 493 494To clear the bits for the file mapped pages associated with the process 495 > echo 3 > /proc/PID/clear_refs 496 497To clear the soft-dirty bit 498 > echo 4 > /proc/PID/clear_refs 499 500To reset the peak resident set size ("high water mark") to the process's 501current value: 502 > echo 5 > /proc/PID/clear_refs 503 504Any other value written to /proc/PID/clear_refs will have no effect. 505 506The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 507using /proc/kpageflags and number of times a page is mapped using 508/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. 509 510The /proc/pid/numa_maps is an extension based on maps, showing the memory 511locality and binding policy, as well as the memory usage (in pages) of 512each mapping. The output follows a general format where mapping details get 513summarized separated by blank spaces, one mapping per each file line: 514 515address policy mapping details 516 51700400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 51800600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5193206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 520320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5213206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5223206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5233206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 524320698b000 default file=/lib64/libc-2.12.so 5253206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 5263206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5273206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 5287f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 5297f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 5307f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 5317fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 5327fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 533 534Where: 535"address" is the starting address for the mapping; 536"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt); 537"mapping details" summarizes mapping data such as mapping type, page usage counters, 538node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 539size, in KB, that is backing the mapping up. 540 5411.2 Kernel data 542--------------- 543 544Similar to the process entries, the kernel data files give information about 545the running kernel. The files used to obtain this information are contained in 546/proc and are listed in Table 1-5. Not all of these will be present in your 547system. It depends on the kernel configuration and the loaded modules, which 548files are there, and which are missing. 549 550Table 1-5: Kernel info in /proc 551.............................................................................. 552 File Content 553 apm Advanced power management info 554 buddyinfo Kernel memory allocator information (see text) (2.5) 555 bus Directory containing bus specific information 556 cmdline Kernel command line 557 cpuinfo Info about the CPU 558 devices Available devices (block and character) 559 dma Used DMS channels 560 filesystems Supported filesystems 561 driver Various drivers grouped here, currently rtc (2.4) 562 execdomains Execdomains, related to security (2.4) 563 fb Frame Buffer devices (2.4) 564 fs File system parameters, currently nfs/exports (2.4) 565 ide Directory containing info about the IDE subsystem 566 interrupts Interrupt usage 567 iomem Memory map (2.4) 568 ioports I/O port usage 569 irq Masks for irq to cpu affinity (2.4)(smp?) 570 isapnp ISA PnP (Plug&Play) Info (2.4) 571 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 572 kmsg Kernel messages 573 ksyms Kernel symbol table 574 loadavg Load average of last 1, 5 & 15 minutes 575 locks Kernel locks 576 meminfo Memory info 577 misc Miscellaneous 578 modules List of loaded modules 579 mounts Mounted filesystems 580 net Networking info (see text) 581 pagetypeinfo Additional page allocator information (see text) (2.5) 582 partitions Table of partitions known to the system 583 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 584 decoupled by lspci (2.4) 585 rtc Real time clock 586 scsi SCSI info (see text) 587 slabinfo Slab pool info 588 softirqs softirq usage 589 stat Overall statistics 590 swaps Swap space utilization 591 sys See chapter 2 592 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 593 tty Info of tty drivers 594 uptime Wall clock since boot, combined idle time of all cpus 595 version Kernel version 596 video bttv info of video resources (2.4) 597 vmallocinfo Show vmalloced areas 598.............................................................................. 599 600You can, for example, check which interrupts are currently in use and what 601they are used for by looking in the file /proc/interrupts: 602 603 > cat /proc/interrupts 604 CPU0 605 0: 8728810 XT-PIC timer 606 1: 895 XT-PIC keyboard 607 2: 0 XT-PIC cascade 608 3: 531695 XT-PIC aha152x 609 4: 2014133 XT-PIC serial 610 5: 44401 XT-PIC pcnet_cs 611 8: 2 XT-PIC rtc 612 11: 8 XT-PIC i82365 613 12: 182918 XT-PIC PS/2 Mouse 614 13: 1 XT-PIC fpu 615 14: 1232265 XT-PIC ide0 616 15: 7 XT-PIC ide1 617 NMI: 0 618 619In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 620output of a SMP machine): 621 622 > cat /proc/interrupts 623 624 CPU0 CPU1 625 0: 1243498 1214548 IO-APIC-edge timer 626 1: 8949 8958 IO-APIC-edge keyboard 627 2: 0 0 XT-PIC cascade 628 5: 11286 10161 IO-APIC-edge soundblaster 629 8: 1 0 IO-APIC-edge rtc 630 9: 27422 27407 IO-APIC-edge 3c503 631 12: 113645 113873 IO-APIC-edge PS/2 Mouse 632 13: 0 0 XT-PIC fpu 633 14: 22491 24012 IO-APIC-edge ide0 634 15: 2183 2415 IO-APIC-edge ide1 635 17: 30564 30414 IO-APIC-level eth0 636 18: 177 164 IO-APIC-level bttv 637 NMI: 2457961 2457959 638 LOC: 2457882 2457881 639 ERR: 2155 640 641NMI is incremented in this case because every timer interrupt generates a NMI 642(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 643 644LOC is the local interrupt counter of the internal APIC of every CPU. 645 646ERR is incremented in the case of errors in the IO-APIC bus (the bus that 647connects the CPUs in a SMP system. This means that an error has been detected, 648the IO-APIC automatically retry the transmission, so it should not be a big 649problem, but you should read the SMP-FAQ. 650 651In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 652/proc/interrupts to display every IRQ vector in use by the system, not 653just those considered 'most important'. The new vectors are: 654 655 THR -- interrupt raised when a machine check threshold counter 656 (typically counting ECC corrected errors of memory or cache) exceeds 657 a configurable threshold. Only available on some systems. 658 659 TRM -- a thermal event interrupt occurs when a temperature threshold 660 has been exceeded for the CPU. This interrupt may also be generated 661 when the temperature drops back to normal. 662 663 SPU -- a spurious interrupt is some interrupt that was raised then lowered 664 by some IO device before it could be fully processed by the APIC. Hence 665 the APIC sees the interrupt but does not know what device it came from. 666 For this case the APIC will generate the interrupt with a IRQ vector 667 of 0xff. This might also be generated by chipset bugs. 668 669 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 670 sent from one CPU to another per the needs of the OS. Typically, 671 their statistics are used by kernel developers and interested users to 672 determine the occurrence of interrupts of the given type. 673 674The above IRQ vectors are displayed only when relevant. For example, 675the threshold vector does not exist on x86_64 platforms. Others are 676suppressed when the system is a uniprocessor. As of this writing, only 677i386 and x86_64 platforms support the new IRQ vector displays. 678 679Of some interest is the introduction of the /proc/irq directory to 2.4. 680It could be used to set IRQ to CPU affinity, this means that you can "hook" an 681IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 682irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 683prof_cpu_mask. 684 685For example 686 > ls /proc/irq/ 687 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 688 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 689 > ls /proc/irq/0/ 690 smp_affinity 691 692smp_affinity is a bitmask, in which you can specify which CPUs can handle the 693IRQ, you can set it by doing: 694 695 > echo 1 > /proc/irq/10/smp_affinity 696 697This means that only the first CPU will handle the IRQ, but you can also echo 6985 which means that only the first and fourth CPU can handle the IRQ. 699 700The contents of each smp_affinity file is the same by default: 701 702 > cat /proc/irq/0/smp_affinity 703 ffffffff 704 705There is an alternate interface, smp_affinity_list which allows specifying 706a cpu range instead of a bitmask: 707 708 > cat /proc/irq/0/smp_affinity_list 709 1024-1031 710 711The default_smp_affinity mask applies to all non-active IRQs, which are the 712IRQs which have not yet been allocated/activated, and hence which lack a 713/proc/irq/[0-9]* directory. 714 715The node file on an SMP system shows the node to which the device using the IRQ 716reports itself as being attached. This hardware locality information does not 717include information about any possible driver locality preference. 718 719prof_cpu_mask specifies which CPUs are to be profiled by the system wide 720profiler. Default value is ffffffff (all cpus if there are only 32 of them). 721 722The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 723between all the CPUs which are allowed to handle it. As usual the kernel has 724more info than you and does a better job than you, so the defaults are the 725best choice for almost everyone. [Note this applies only to those IO-APIC's 726that support "Round Robin" interrupt distribution.] 727 728There are three more important subdirectories in /proc: net, scsi, and sys. 729The general rule is that the contents, or even the existence of these 730directories, depend on your kernel configuration. If SCSI is not enabled, the 731directory scsi may not exist. The same is true with the net, which is there 732only when networking support is present in the running kernel. 733 734The slabinfo file gives information about memory usage at the slab level. 735Linux uses slab pools for memory management above page level in version 2.2. 736Commonly used objects have their own slab pool (such as network buffers, 737directory cache, and so on). 738 739.............................................................................. 740 741> cat /proc/buddyinfo 742 743Node 0, zone DMA 0 4 5 4 4 3 ... 744Node 0, zone Normal 1 0 0 1 101 8 ... 745Node 0, zone HighMem 2 0 0 1 1 0 ... 746 747External fragmentation is a problem under some workloads, and buddyinfo is a 748useful tool for helping diagnose these problems. Buddyinfo will give you a 749clue as to how big an area you can safely allocate, or why a previous 750allocation failed. 751 752Each column represents the number of pages of a certain order which are 753available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 754ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 755available in ZONE_NORMAL, etc... 756 757More information relevant to external fragmentation can be found in 758pagetypeinfo. 759 760> cat /proc/pagetypeinfo 761Page block order: 9 762Pages per block: 512 763 764Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 765Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 766Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 767Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 768Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 769Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 770Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 771Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 772Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 773Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 774Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 775 776Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 777Node 0, zone DMA 2 0 5 1 0 778Node 0, zone DMA32 41 6 967 2 0 779 780Fragmentation avoidance in the kernel works by grouping pages of different 781migrate types into the same contiguous regions of memory called page blocks. 782A page block is typically the size of the default hugepage size e.g. 2MB on 783X86-64. By keeping pages grouped based on their ability to move, the kernel 784can reclaim pages within a page block to satisfy a high-order allocation. 785 786The pagetypinfo begins with information on the size of a page block. It 787then gives the same type of information as buddyinfo except broken down 788by migrate-type and finishes with details on how many page blocks of each 789type exist. 790 791If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 792from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can 793make an estimate of the likely number of huge pages that can be allocated 794at a given point in time. All the "Movable" blocks should be allocatable 795unless memory has been mlock()'d. Some of the Reclaimable blocks should 796also be allocatable although a lot of filesystem metadata may have to be 797reclaimed to achieve this. 798 799.............................................................................. 800 801meminfo: 802 803Provides information about distribution and utilization of memory. This 804varies by architecture and compile options. The following is from a 80516GB PIII, which has highmem enabled. You may not have all of these fields. 806 807> cat /proc/meminfo 808 809The "Locked" indicates whether the mapping is locked in memory or not. 810 811 812MemTotal: 16344972 kB 813MemFree: 13634064 kB 814MemAvailable: 14836172 kB 815Buffers: 3656 kB 816Cached: 1195708 kB 817SwapCached: 0 kB 818Active: 891636 kB 819Inactive: 1077224 kB 820HighTotal: 15597528 kB 821HighFree: 13629632 kB 822LowTotal: 747444 kB 823LowFree: 4432 kB 824SwapTotal: 0 kB 825SwapFree: 0 kB 826Dirty: 968 kB 827Writeback: 0 kB 828AnonPages: 861800 kB 829Mapped: 280372 kB 830Slab: 284364 kB 831SReclaimable: 159856 kB 832SUnreclaim: 124508 kB 833PageTables: 24448 kB 834NFS_Unstable: 0 kB 835Bounce: 0 kB 836WritebackTmp: 0 kB 837CommitLimit: 7669796 kB 838Committed_AS: 100056 kB 839VmallocTotal: 112216 kB 840VmallocUsed: 428 kB 841VmallocChunk: 111088 kB 842AnonHugePages: 49152 kB 843 844 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 845 bits and the kernel binary code) 846 MemFree: The sum of LowFree+HighFree 847MemAvailable: An estimate of how much memory is available for starting new 848 applications, without swapping. Calculated from MemFree, 849 SReclaimable, the size of the file LRU lists, and the low 850 watermarks in each zone. 851 The estimate takes into account that the system needs some 852 page cache to function well, and that not all reclaimable 853 slab will be reclaimable, due to items being in use. The 854 impact of those factors will vary from system to system. 855 Buffers: Relatively temporary storage for raw disk blocks 856 shouldn't get tremendously large (20MB or so) 857 Cached: in-memory cache for files read from the disk (the 858 pagecache). Doesn't include SwapCached 859 SwapCached: Memory that once was swapped out, is swapped back in but 860 still also is in the swapfile (if memory is needed it 861 doesn't need to be swapped out AGAIN because it is already 862 in the swapfile. This saves I/O) 863 Active: Memory that has been used more recently and usually not 864 reclaimed unless absolutely necessary. 865 Inactive: Memory which has been less recently used. It is more 866 eligible to be reclaimed for other purposes 867 HighTotal: 868 HighFree: Highmem is all memory above ~860MB of physical memory 869 Highmem areas are for use by userspace programs, or 870 for the pagecache. The kernel must use tricks to access 871 this memory, making it slower to access than lowmem. 872 LowTotal: 873 LowFree: Lowmem is memory which can be used for everything that 874 highmem can be used for, but it is also available for the 875 kernel's use for its own data structures. Among many 876 other things, it is where everything from the Slab is 877 allocated. Bad things happen when you're out of lowmem. 878 SwapTotal: total amount of swap space available 879 SwapFree: Memory which has been evicted from RAM, and is temporarily 880 on the disk 881 Dirty: Memory which is waiting to get written back to the disk 882 Writeback: Memory which is actively being written back to the disk 883 AnonPages: Non-file backed pages mapped into userspace page tables 884AnonHugePages: Non-file backed huge pages mapped into userspace page tables 885 Mapped: files which have been mmaped, such as libraries 886 Slab: in-kernel data structures cache 887SReclaimable: Part of Slab, that might be reclaimed, such as caches 888 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 889 PageTables: amount of memory dedicated to the lowest level of page 890 tables. 891NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 892 storage 893 Bounce: Memory used for block device "bounce buffers" 894WritebackTmp: Memory used by FUSE for temporary writeback buffers 895 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 896 this is the total amount of memory currently available to 897 be allocated on the system. This limit is only adhered to 898 if strict overcommit accounting is enabled (mode 2 in 899 'vm.overcommit_memory'). 900 The CommitLimit is calculated with the following formula: 901 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 902 overcommit_ratio / 100 + [total swap pages] 903 For example, on a system with 1G of physical RAM and 7G 904 of swap with a `vm.overcommit_ratio` of 30 it would 905 yield a CommitLimit of 7.3G. 906 For more details, see the memory overcommit documentation 907 in vm/overcommit-accounting. 908Committed_AS: The amount of memory presently allocated on the system. 909 The committed memory is a sum of all of the memory which 910 has been allocated by processes, even if it has not been 911 "used" by them as of yet. A process which malloc()'s 1G 912 of memory, but only touches 300M of it will show up as 913 using 1G. This 1G is memory which has been "committed" to 914 by the VM and can be used at any time by the allocating 915 application. With strict overcommit enabled on the system 916 (mode 2 in 'vm.overcommit_memory'),allocations which would 917 exceed the CommitLimit (detailed above) will not be permitted. 918 This is useful if one needs to guarantee that processes will 919 not fail due to lack of memory once that memory has been 920 successfully allocated. 921VmallocTotal: total size of vmalloc memory area 922 VmallocUsed: amount of vmalloc area which is used 923VmallocChunk: largest contiguous block of vmalloc area which is free 924 925.............................................................................. 926 927vmallocinfo: 928 929Provides information about vmalloced/vmaped areas. One line per area, 930containing the virtual address range of the area, size in bytes, 931caller information of the creator, and optional information depending 932on the kind of area : 933 934 pages=nr number of pages 935 phys=addr if a physical address was specified 936 ioremap I/O mapping (ioremap() and friends) 937 vmalloc vmalloc() area 938 vmap vmap()ed pages 939 user VM_USERMAP area 940 vpages buffer for pages pointers was vmalloced (huge area) 941 N<node>=nr (Only on NUMA kernels) 942 Number of pages allocated on memory node <node> 943 944> cat /proc/vmallocinfo 9450xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 946 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 9470xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 948 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 9490xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 950 phys=7fee8000 ioremap 9510xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 952 phys=7fee7000 ioremap 9530xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 9540xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 955 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 9560xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 957 pages=2 vmalloc N1=2 9580xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 959 /0x130 [x_tables] pages=4 vmalloc N0=4 9600xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 961 pages=14 vmalloc N2=14 9620xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 963 pages=4 vmalloc N1=4 9640xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 965 pages=2 vmalloc N1=2 9660xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 967 pages=10 vmalloc N0=10 968 969.............................................................................. 970 971softirqs: 972 973Provides counts of softirq handlers serviced since boot time, for each cpu. 974 975> cat /proc/softirqs 976 CPU0 CPU1 CPU2 CPU3 977 HI: 0 0 0 0 978 TIMER: 27166 27120 27097 27034 979 NET_TX: 0 0 0 17 980 NET_RX: 42 0 0 39 981 BLOCK: 0 0 107 1121 982 TASKLET: 0 0 0 290 983 SCHED: 27035 26983 26971 26746 984 HRTIMER: 0 0 0 0 985 RCU: 1678 1769 2178 2250 986 987 9881.3 IDE devices in /proc/ide 989---------------------------- 990 991The subdirectory /proc/ide contains information about all IDE devices of which 992the kernel is aware. There is one subdirectory for each IDE controller, the 993file drivers and a link for each IDE device, pointing to the device directory 994in the controller specific subtree. 995 996The file drivers contains general information about the drivers used for the 997IDE devices: 998 999 > cat /proc/ide/drivers 1000 ide-cdrom version 4.53 1001 ide-disk version 1.08 1002 1003More detailed information can be found in the controller specific 1004subdirectories. These are named ide0, ide1 and so on. Each of these 1005directories contains the files shown in table 1-6. 1006 1007 1008Table 1-6: IDE controller info in /proc/ide/ide? 1009.............................................................................. 1010 File Content 1011 channel IDE channel (0 or 1) 1012 config Configuration (only for PCI/IDE bridge) 1013 mate Mate name 1014 model Type/Chipset of IDE controller 1015.............................................................................. 1016 1017Each device connected to a controller has a separate subdirectory in the 1018controllers directory. The files listed in table 1-7 are contained in these 1019directories. 1020 1021 1022Table 1-7: IDE device information 1023.............................................................................. 1024 File Content 1025 cache The cache 1026 capacity Capacity of the medium (in 512Byte blocks) 1027 driver driver and version 1028 geometry physical and logical geometry 1029 identify device identify block 1030 media media type 1031 model device identifier 1032 settings device setup 1033 smart_thresholds IDE disk management thresholds 1034 smart_values IDE disk management values 1035.............................................................................. 1036 1037The most interesting file is settings. This file contains a nice overview of 1038the drive parameters: 1039 1040 # cat /proc/ide/ide0/hda/settings 1041 name value min max mode 1042 ---- ----- --- --- ---- 1043 bios_cyl 526 0 65535 rw 1044 bios_head 255 0 255 rw 1045 bios_sect 63 0 63 rw 1046 breada_readahead 4 0 127 rw 1047 bswap 0 0 1 r 1048 file_readahead 72 0 2097151 rw 1049 io_32bit 0 0 3 rw 1050 keepsettings 0 0 1 rw 1051 max_kb_per_request 122 1 127 rw 1052 multcount 0 0 8 rw 1053 nice1 1 0 1 rw 1054 nowerr 0 0 1 rw 1055 pio_mode write-only 0 255 w 1056 slow 0 0 1 rw 1057 unmaskirq 0 0 1 rw 1058 using_dma 0 0 1 rw 1059 1060 10611.4 Networking info in /proc/net 1062-------------------------------- 1063 1064The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1065additional values you get for IP version 6 if you configure the kernel to 1066support this. Table 1-9 lists the files and their meaning. 1067 1068 1069Table 1-8: IPv6 info in /proc/net 1070.............................................................................. 1071 File Content 1072 udp6 UDP sockets (IPv6) 1073 tcp6 TCP sockets (IPv6) 1074 raw6 Raw device statistics (IPv6) 1075 igmp6 IP multicast addresses, which this host joined (IPv6) 1076 if_inet6 List of IPv6 interface addresses 1077 ipv6_route Kernel routing table for IPv6 1078 rt6_stats Global IPv6 routing tables statistics 1079 sockstat6 Socket statistics (IPv6) 1080 snmp6 Snmp data (IPv6) 1081.............................................................................. 1082 1083 1084Table 1-9: Network info in /proc/net 1085.............................................................................. 1086 File Content 1087 arp Kernel ARP table 1088 dev network devices with statistics 1089 dev_mcast the Layer2 multicast groups a device is listening too 1090 (interface index, label, number of references, number of bound 1091 addresses). 1092 dev_stat network device status 1093 ip_fwchains Firewall chain linkage 1094 ip_fwnames Firewall chain names 1095 ip_masq Directory containing the masquerading tables 1096 ip_masquerade Major masquerading table 1097 netstat Network statistics 1098 raw raw device statistics 1099 route Kernel routing table 1100 rpc Directory containing rpc info 1101 rt_cache Routing cache 1102 snmp SNMP data 1103 sockstat Socket statistics 1104 tcp TCP sockets 1105 udp UDP sockets 1106 unix UNIX domain sockets 1107 wireless Wireless interface data (Wavelan etc) 1108 igmp IP multicast addresses, which this host joined 1109 psched Global packet scheduler parameters. 1110 netlink List of PF_NETLINK sockets 1111 ip_mr_vifs List of multicast virtual interfaces 1112 ip_mr_cache List of multicast routing cache 1113.............................................................................. 1114 1115You can use this information to see which network devices are available in 1116your system and how much traffic was routed over those devices: 1117 1118 > cat /proc/net/dev 1119 Inter-|Receive |[... 1120 face |bytes packets errs drop fifo frame compressed multicast|[... 1121 lo: 908188 5596 0 0 0 0 0 0 [... 1122 ppp0:15475140 20721 410 0 0 410 0 0 [... 1123 eth0: 614530 7085 0 0 0 0 0 1 [... 1124 1125 ...] Transmit 1126 ...] bytes packets errs drop fifo colls carrier compressed 1127 ...] 908188 5596 0 0 0 0 0 0 1128 ...] 1375103 17405 0 0 0 0 0 0 1129 ...] 1703981 5535 0 0 0 3 0 0 1130 1131In addition, each Channel Bond interface has its own directory. For 1132example, the bond0 device will have a directory called /proc/net/bond0/. 1133It will contain information that is specific to that bond, such as the 1134current slaves of the bond, the link status of the slaves, and how 1135many times the slaves link has failed. 1136 11371.5 SCSI info 1138------------- 1139 1140If you have a SCSI host adapter in your system, you'll find a subdirectory 1141named after the driver for this adapter in /proc/scsi. You'll also see a list 1142of all recognized SCSI devices in /proc/scsi: 1143 1144 >cat /proc/scsi/scsi 1145 Attached devices: 1146 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1147 Vendor: IBM Model: DGHS09U Rev: 03E0 1148 Type: Direct-Access ANSI SCSI revision: 03 1149 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1150 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1151 Type: CD-ROM ANSI SCSI revision: 02 1152 1153 1154The directory named after the driver has one file for each adapter found in 1155the system. These files contain information about the controller, including 1156the used IRQ and the IO address range. The amount of information shown is 1157dependent on the adapter you use. The example shows the output for an Adaptec 1158AHA-2940 SCSI adapter: 1159 1160 > cat /proc/scsi/aic7xxx/0 1161 1162 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1163 Compile Options: 1164 TCQ Enabled By Default : Disabled 1165 AIC7XXX_PROC_STATS : Disabled 1166 AIC7XXX_RESET_DELAY : 5 1167 Adapter Configuration: 1168 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1169 Ultra Wide Controller 1170 PCI MMAPed I/O Base: 0xeb001000 1171 Adapter SEEPROM Config: SEEPROM found and used. 1172 Adaptec SCSI BIOS: Enabled 1173 IRQ: 10 1174 SCBs: Active 0, Max Active 2, 1175 Allocated 15, HW 16, Page 255 1176 Interrupts: 160328 1177 BIOS Control Word: 0x18b6 1178 Adapter Control Word: 0x005b 1179 Extended Translation: Enabled 1180 Disconnect Enable Flags: 0xffff 1181 Ultra Enable Flags: 0x0001 1182 Tag Queue Enable Flags: 0x0000 1183 Ordered Queue Tag Flags: 0x0000 1184 Default Tag Queue Depth: 8 1185 Tagged Queue By Device array for aic7xxx host instance 0: 1186 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1187 Actual queue depth per device for aic7xxx host instance 0: 1188 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1189 Statistics: 1190 (scsi0:0:0:0) 1191 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1192 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1193 Total transfers 160151 (74577 reads and 85574 writes) 1194 (scsi0:0:6:0) 1195 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1196 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1197 Total transfers 0 (0 reads and 0 writes) 1198 1199 12001.6 Parallel port info in /proc/parport 1201--------------------------------------- 1202 1203The directory /proc/parport contains information about the parallel ports of 1204your system. It has one subdirectory for each port, named after the port 1205number (0,1,2,...). 1206 1207These directories contain the four files shown in Table 1-10. 1208 1209 1210Table 1-10: Files in /proc/parport 1211.............................................................................. 1212 File Content 1213 autoprobe Any IEEE-1284 device ID information that has been acquired. 1214 devices list of the device drivers using that port. A + will appear by the 1215 name of the device currently using the port (it might not appear 1216 against any). 1217 hardware Parallel port's base address, IRQ line and DMA channel. 1218 irq IRQ that parport is using for that port. This is in a separate 1219 file to allow you to alter it by writing a new value in (IRQ 1220 number or none). 1221.............................................................................. 1222 12231.7 TTY info in /proc/tty 1224------------------------- 1225 1226Information about the available and actually used tty's can be found in the 1227directory /proc/tty.You'll find entries for drivers and line disciplines in 1228this directory, as shown in Table 1-11. 1229 1230 1231Table 1-11: Files in /proc/tty 1232.............................................................................. 1233 File Content 1234 drivers list of drivers and their usage 1235 ldiscs registered line disciplines 1236 driver/serial usage statistic and status of single tty lines 1237.............................................................................. 1238 1239To see which tty's are currently in use, you can simply look into the file 1240/proc/tty/drivers: 1241 1242 > cat /proc/tty/drivers 1243 pty_slave /dev/pts 136 0-255 pty:slave 1244 pty_master /dev/ptm 128 0-255 pty:master 1245 pty_slave /dev/ttyp 3 0-255 pty:slave 1246 pty_master /dev/pty 2 0-255 pty:master 1247 serial /dev/cua 5 64-67 serial:callout 1248 serial /dev/ttyS 4 64-67 serial 1249 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1250 /dev/ptmx /dev/ptmx 5 2 system 1251 /dev/console /dev/console 5 1 system:console 1252 /dev/tty /dev/tty 5 0 system:/dev/tty 1253 unknown /dev/tty 4 1-63 console 1254 1255 12561.8 Miscellaneous kernel statistics in /proc/stat 1257------------------------------------------------- 1258 1259Various pieces of information about kernel activity are available in the 1260/proc/stat file. All of the numbers reported in this file are aggregates 1261since the system first booted. For a quick look, simply cat the file: 1262 1263 > cat /proc/stat 1264 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1265 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1266 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1267 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1268 ctxt 1990473 1269 btime 1062191376 1270 processes 2915 1271 procs_running 1 1272 procs_blocked 0 1273 softirq 183433 0 21755 12 39 1137 231 21459 2263 1274 1275The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1276lines. These numbers identify the amount of time the CPU has spent performing 1277different kinds of work. Time units are in USER_HZ (typically hundredths of a 1278second). The meanings of the columns are as follows, from left to right: 1279 1280- user: normal processes executing in user mode 1281- nice: niced processes executing in user mode 1282- system: processes executing in kernel mode 1283- idle: twiddling thumbs 1284- iowait: waiting for I/O to complete 1285- irq: servicing interrupts 1286- softirq: servicing softirqs 1287- steal: involuntary wait 1288- guest: running a normal guest 1289- guest_nice: running a niced guest 1290 1291The "intr" line gives counts of interrupts serviced since boot time, for each 1292of the possible system interrupts. The first column is the total of all 1293interrupts serviced including unnumbered architecture specific interrupts; 1294each subsequent column is the total for that particular numbered interrupt. 1295Unnumbered interrupts are not shown, only summed into the total. 1296 1297The "ctxt" line gives the total number of context switches across all CPUs. 1298 1299The "btime" line gives the time at which the system booted, in seconds since 1300the Unix epoch. 1301 1302The "processes" line gives the number of processes and threads created, which 1303includes (but is not limited to) those created by calls to the fork() and 1304clone() system calls. 1305 1306The "procs_running" line gives the total number of threads that are 1307running or ready to run (i.e., the total number of runnable threads). 1308 1309The "procs_blocked" line gives the number of processes currently blocked, 1310waiting for I/O to complete. 1311 1312The "softirq" line gives counts of softirqs serviced since boot time, for each 1313of the possible system softirqs. The first column is the total of all 1314softirqs serviced; each subsequent column is the total for that particular 1315softirq. 1316 1317 13181.9 Ext4 file system parameters 1319------------------------------- 1320 1321Information about mounted ext4 file systems can be found in 1322/proc/fs/ext4. Each mounted filesystem will have a directory in 1323/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1324/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1325in Table 1-12, below. 1326 1327Table 1-12: Files in /proc/fs/ext4/<devname> 1328.............................................................................. 1329 File Content 1330 mb_groups details of multiblock allocator buddy cache of free blocks 1331.............................................................................. 1332 13332.0 /proc/consoles 1334------------------ 1335Shows registered system console lines. 1336 1337To see which character device lines are currently used for the system console 1338/dev/console, you may simply look into the file /proc/consoles: 1339 1340 > cat /proc/consoles 1341 tty0 -WU (ECp) 4:7 1342 ttyS0 -W- (Ep) 4:64 1343 1344The columns are: 1345 1346 device name of the device 1347 operations R = can do read operations 1348 W = can do write operations 1349 U = can do unblank 1350 flags E = it is enabled 1351 C = it is preferred console 1352 B = it is primary boot console 1353 p = it is used for printk buffer 1354 b = it is not a TTY but a Braille device 1355 a = it is safe to use when cpu is offline 1356 major:minor major and minor number of the device separated by a colon 1357 1358------------------------------------------------------------------------------ 1359Summary 1360------------------------------------------------------------------------------ 1361The /proc file system serves information about the running system. It not only 1362allows access to process data but also allows you to request the kernel status 1363by reading files in the hierarchy. 1364 1365The directory structure of /proc reflects the types of information and makes 1366it easy, if not obvious, where to look for specific data. 1367------------------------------------------------------------------------------ 1368 1369------------------------------------------------------------------------------ 1370CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1371------------------------------------------------------------------------------ 1372 1373------------------------------------------------------------------------------ 1374In This Chapter 1375------------------------------------------------------------------------------ 1376* Modifying kernel parameters by writing into files found in /proc/sys 1377* Exploring the files which modify certain parameters 1378* Review of the /proc/sys file tree 1379------------------------------------------------------------------------------ 1380 1381 1382A very interesting part of /proc is the directory /proc/sys. This is not only 1383a source of information, it also allows you to change parameters within the 1384kernel. Be very careful when attempting this. You can optimize your system, 1385but you can also cause it to crash. Never alter kernel parameters on a 1386production system. Set up a development machine and test to make sure that 1387everything works the way you want it to. You may have no alternative but to 1388reboot the machine once an error has been made. 1389 1390To change a value, simply echo the new value into the file. An example is 1391given below in the section on the file system data. You need to be root to do 1392this. You can create your own boot script to perform this every time your 1393system boots. 1394 1395The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1396general things in the operation of the Linux kernel. Since some of the files 1397can inadvertently disrupt your system, it is advisable to read both 1398documentation and source before actually making adjustments. In any case, be 1399very careful when writing to any of these files. The entries in /proc may 1400change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1401review the kernel documentation in the directory /usr/src/linux/Documentation. 1402This chapter is heavily based on the documentation included in the pre 2.2 1403kernels, and became part of it in version 2.2.1 of the Linux kernel. 1404 1405Please see: Documentation/sysctl/ directory for descriptions of these 1406entries. 1407 1408------------------------------------------------------------------------------ 1409Summary 1410------------------------------------------------------------------------------ 1411Certain aspects of kernel behavior can be modified at runtime, without the 1412need to recompile the kernel, or even to reboot the system. The files in the 1413/proc/sys tree can not only be read, but also modified. You can use the echo 1414command to write value into these files, thereby changing the default settings 1415of the kernel. 1416------------------------------------------------------------------------------ 1417 1418------------------------------------------------------------------------------ 1419CHAPTER 3: PER-PROCESS PARAMETERS 1420------------------------------------------------------------------------------ 1421 14223.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1423-------------------------------------------------------------------------------- 1424 1425These file can be used to adjust the badness heuristic used to select which 1426process gets killed in out of memory conditions. 1427 1428The badness heuristic assigns a value to each candidate task ranging from 0 1429(never kill) to 1000 (always kill) to determine which process is targeted. The 1430units are roughly a proportion along that range of allowed memory the process 1431may allocate from based on an estimation of its current memory and swap use. 1432For example, if a task is using all allowed memory, its badness score will be 14331000. If it is using half of its allowed memory, its score will be 500. 1434 1435There is an additional factor included in the badness score: the current memory 1436and swap usage is discounted by 3% for root processes. 1437 1438The amount of "allowed" memory depends on the context in which the oom killer 1439was called. If it is due to the memory assigned to the allocating task's cpuset 1440being exhausted, the allowed memory represents the set of mems assigned to that 1441cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1442memory represents the set of mempolicy nodes. If it is due to a memory 1443limit (or swap limit) being reached, the allowed memory is that configured 1444limit. Finally, if it is due to the entire system being out of memory, the 1445allowed memory represents all allocatable resources. 1446 1447The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1448is used to determine which task to kill. Acceptable values range from -1000 1449(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1450polarize the preference for oom killing either by always preferring a certain 1451task or completely disabling it. The lowest possible value, -1000, is 1452equivalent to disabling oom killing entirely for that task since it will always 1453report a badness score of 0. 1454 1455Consequently, it is very simple for userspace to define the amount of memory to 1456consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1457example, is roughly equivalent to allowing the remainder of tasks sharing the 1458same system, cpuset, mempolicy, or memory controller resources to use at least 145950% more memory. A value of -500, on the other hand, would be roughly 1460equivalent to discounting 50% of the task's allowed memory from being considered 1461as scoring against the task. 1462 1463For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1464be used to tune the badness score. Its acceptable values range from -16 1465(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1466(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1467scaled linearly with /proc/<pid>/oom_score_adj. 1468 1469The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1470value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1471requires CAP_SYS_RESOURCE. 1472 1473Caveat: when a parent task is selected, the oom killer will sacrifice any first 1474generation children with separate address spaces instead, if possible. This 1475avoids servers and important system daemons from being killed and loses the 1476minimal amount of work. 1477 1478 14793.2 /proc/<pid>/oom_score - Display current oom-killer score 1480------------------------------------------------------------- 1481 1482This file can be used to check the current score used by the oom-killer is for 1483any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1484process should be killed in an out-of-memory situation. 1485 1486 14873.3 /proc/<pid>/io - Display the IO accounting fields 1488------------------------------------------------------- 1489 1490This file contains IO statistics for each running process 1491 1492Example 1493------- 1494 1495test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1496[1] 3828 1497 1498test:/tmp # cat /proc/3828/io 1499rchar: 323934931 1500wchar: 323929600 1501syscr: 632687 1502syscw: 632675 1503read_bytes: 0 1504write_bytes: 323932160 1505cancelled_write_bytes: 0 1506 1507 1508Description 1509----------- 1510 1511rchar 1512----- 1513 1514I/O counter: chars read 1515The number of bytes which this task has caused to be read from storage. This 1516is simply the sum of bytes which this process passed to read() and pread(). 1517It includes things like tty IO and it is unaffected by whether or not actual 1518physical disk IO was required (the read might have been satisfied from 1519pagecache) 1520 1521 1522wchar 1523----- 1524 1525I/O counter: chars written 1526The number of bytes which this task has caused, or shall cause to be written 1527to disk. Similar caveats apply here as with rchar. 1528 1529 1530syscr 1531----- 1532 1533I/O counter: read syscalls 1534Attempt to count the number of read I/O operations, i.e. syscalls like read() 1535and pread(). 1536 1537 1538syscw 1539----- 1540 1541I/O counter: write syscalls 1542Attempt to count the number of write I/O operations, i.e. syscalls like 1543write() and pwrite(). 1544 1545 1546read_bytes 1547---------- 1548 1549I/O counter: bytes read 1550Attempt to count the number of bytes which this process really did cause to 1551be fetched from the storage layer. Done at the submit_bio() level, so it is 1552accurate for block-backed filesystems. <please add status regarding NFS and 1553CIFS at a later time> 1554 1555 1556write_bytes 1557----------- 1558 1559I/O counter: bytes written 1560Attempt to count the number of bytes which this process caused to be sent to 1561the storage layer. This is done at page-dirtying time. 1562 1563 1564cancelled_write_bytes 1565--------------------- 1566 1567The big inaccuracy here is truncate. If a process writes 1MB to a file and 1568then deletes the file, it will in fact perform no writeout. But it will have 1569been accounted as having caused 1MB of write. 1570In other words: The number of bytes which this process caused to not happen, 1571by truncating pagecache. A task can cause "negative" IO too. If this task 1572truncates some dirty pagecache, some IO which another task has been accounted 1573for (in its write_bytes) will not be happening. We _could_ just subtract that 1574from the truncating task's write_bytes, but there is information loss in doing 1575that. 1576 1577 1578Note 1579---- 1580 1581At its current implementation state, this is a bit racy on 32-bit machines: if 1582process A reads process B's /proc/pid/io while process B is updating one of 1583those 64-bit counters, process A could see an intermediate result. 1584 1585 1586More information about this can be found within the taskstats documentation in 1587Documentation/accounting. 1588 15893.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1590--------------------------------------------------------------- 1591When a process is dumped, all anonymous memory is written to a core file as 1592long as the size of the core file isn't limited. But sometimes we don't want 1593to dump some memory segments, for example, huge shared memory. Conversely, 1594sometimes we want to save file-backed memory segments into a core file, not 1595only the individual files. 1596 1597/proc/<pid>/coredump_filter allows you to customize which memory segments 1598will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1599of memory types. If a bit of the bitmask is set, memory segments of the 1600corresponding memory type are dumped, otherwise they are not dumped. 1601 1602The following 7 memory types are supported: 1603 - (bit 0) anonymous private memory 1604 - (bit 1) anonymous shared memory 1605 - (bit 2) file-backed private memory 1606 - (bit 3) file-backed shared memory 1607 - (bit 4) ELF header pages in file-backed private memory areas (it is 1608 effective only if the bit 2 is cleared) 1609 - (bit 5) hugetlb private memory 1610 - (bit 6) hugetlb shared memory 1611 1612 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1613 are always dumped regardless of the bitmask status. 1614 1615 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only 1616 effected by bit 5-6. 1617 1618Default value of coredump_filter is 0x23; this means all anonymous memory 1619segments and hugetlb private memory are dumped. 1620 1621If you don't want to dump all shared memory segments attached to pid 1234, 1622write 0x21 to the process's proc file. 1623 1624 $ echo 0x21 > /proc/1234/coredump_filter 1625 1626When a new process is created, the process inherits the bitmask status from its 1627parent. It is useful to set up coredump_filter before the program runs. 1628For example: 1629 1630 $ echo 0x7 > /proc/self/coredump_filter 1631 $ ./some_program 1632 16333.5 /proc/<pid>/mountinfo - Information about mounts 1634-------------------------------------------------------- 1635 1636This file contains lines of the form: 1637 163836 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1639(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1640 1641(1) mount ID: unique identifier of the mount (may be reused after umount) 1642(2) parent ID: ID of parent (or of self for the top of the mount tree) 1643(3) major:minor: value of st_dev for files on filesystem 1644(4) root: root of the mount within the filesystem 1645(5) mount point: mount point relative to the process's root 1646(6) mount options: per mount options 1647(7) optional fields: zero or more fields of the form "tag[:value]" 1648(8) separator: marks the end of the optional fields 1649(9) filesystem type: name of filesystem of the form "type[.subtype]" 1650(10) mount source: filesystem specific information or "none" 1651(11) super options: per super block options 1652 1653Parsers should ignore all unrecognised optional fields. Currently the 1654possible optional fields are: 1655 1656shared:X mount is shared in peer group X 1657master:X mount is slave to peer group X 1658propagate_from:X mount is slave and receives propagation from peer group X (*) 1659unbindable mount is unbindable 1660 1661(*) X is the closest dominant peer group under the process's root. If 1662X is the immediate master of the mount, or if there's no dominant peer 1663group under the same root, then only the "master:X" field is present 1664and not the "propagate_from:X" field. 1665 1666For more information on mount propagation see: 1667 1668 Documentation/filesystems/sharedsubtree.txt 1669 1670 16713.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1672-------------------------------------------------------- 1673These files provide a method to access a tasks comm value. It also allows for 1674a task to set its own or one of its thread siblings comm value. The comm value 1675is limited in size compared to the cmdline value, so writing anything longer 1676then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1677comm value. 1678 1679 16803.7 /proc/<pid>/task/<tid>/children - Information about task children 1681------------------------------------------------------------------------- 1682This file provides a fast way to retrieve first level children pids 1683of a task pointed by <pid>/<tid> pair. The format is a space separated 1684stream of pids. 1685 1686Note the "first level" here -- if a child has own children they will 1687not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children 1688to obtain the descendants. 1689 1690Since this interface is intended to be fast and cheap it doesn't 1691guarantee to provide precise results and some children might be 1692skipped, especially if they've exited right after we printed their 1693pids, so one need to either stop or freeze processes being inspected 1694if precise results are needed. 1695 1696 16973.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1698--------------------------------------------------------------- 1699This file provides information associated with an opened file. The regular 1700files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos' 1701represents the current offset of the opened file in decimal form [see lseek(2) 1702for details], 'flags' denotes the octal O_xxx mask the file has been 1703created with [see open(2) for details] and 'mnt_id' represents mount ID of 1704the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo 1705for details]. 1706 1707A typical output is 1708 1709 pos: 0 1710 flags: 0100002 1711 mnt_id: 19 1712 1713All locks associated with a file descriptor are shown in its fdinfo too. 1714 1715lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1716 1717The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1718pair provide additional information particular to the objects they represent. 1719 1720 Eventfd files 1721 ~~~~~~~~~~~~~ 1722 pos: 0 1723 flags: 04002 1724 mnt_id: 9 1725 eventfd-count: 5a 1726 1727 where 'eventfd-count' is hex value of a counter. 1728 1729 Signalfd files 1730 ~~~~~~~~~~~~~~ 1731 pos: 0 1732 flags: 04002 1733 mnt_id: 9 1734 sigmask: 0000000000000200 1735 1736 where 'sigmask' is hex value of the signal mask associated 1737 with a file. 1738 1739 Epoll files 1740 ~~~~~~~~~~~ 1741 pos: 0 1742 flags: 02 1743 mnt_id: 9 1744 tfd: 5 events: 1d data: ffffffffffffffff 1745 1746 where 'tfd' is a target file descriptor number in decimal form, 1747 'events' is events mask being watched and the 'data' is data 1748 associated with a target [see epoll(7) for more details]. 1749 1750 Fsnotify files 1751 ~~~~~~~~~~~~~~ 1752 For inotify files the format is the following 1753 1754 pos: 0 1755 flags: 02000000 1756 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1757 1758 where 'wd' is a watch descriptor in decimal form, ie a target file 1759 descriptor number, 'ino' and 'sdev' are inode and device where the 1760 target file resides and the 'mask' is the mask of events, all in hex 1761 form [see inotify(7) for more details]. 1762 1763 If the kernel was built with exportfs support, the path to the target 1764 file is encoded as a file handle. The file handle is provided by three 1765 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1766 format. 1767 1768 If the kernel is built without exportfs support the file handle won't be 1769 printed out. 1770 1771 If there is no inotify mark attached yet the 'inotify' line will be omitted. 1772 1773 For fanotify files the format is 1774 1775 pos: 0 1776 flags: 02 1777 mnt_id: 9 1778 fanotify flags:10 event-flags:0 1779 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1780 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1781 1782 where fanotify 'flags' and 'event-flags' are values used in fanotify_init 1783 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 1784 flags associated with mark which are tracked separately from events 1785 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events 1786 mask and 'ignored_mask' is the mask of events which are to be ignored. 1787 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 1788 does provide information about flags and mask used in fanotify_mark 1789 call [see fsnotify manpage for details]. 1790 1791 While the first three lines are mandatory and always printed, the rest is 1792 optional and may be omitted if no marks created yet. 1793 1794 Timerfd files 1795 ~~~~~~~~~~~~~ 1796 1797 pos: 0 1798 flags: 02 1799 mnt_id: 9 1800 clockid: 0 1801 ticks: 0 1802 settime flags: 01 1803 it_value: (0, 49406829) 1804 it_interval: (1, 0) 1805 1806 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 1807 that have occurred [see timerfd_create(2) for details]. 'settime flags' are 1808 flags in octal form been used to setup the timer [see timerfd_settime(2) for 1809 details]. 'it_value' is remaining time until the timer exiration. 1810 'it_interval' is the interval for the timer. Note the timer might be set up 1811 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 1812 still exhibits timer's remaining time. 1813 18143.9 /proc/<pid>/map_files - Information about memory mapped files 1815--------------------------------------------------------------------- 1816This directory contains symbolic links which represent memory mapped files 1817the process is maintaining. Example output: 1818 1819 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 1820 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 1821 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 1822 | ... 1823 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 1824 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 1825 1826The name of a link represents the virtual memory bounds of a mapping, i.e. 1827vm_area_struct::vm_start-vm_area_struct::vm_end. 1828 1829The main purpose of the map_files is to retrieve a set of memory mapped 1830files in a fast way instead of parsing /proc/<pid>/maps or 1831/proc/<pid>/smaps, both of which contain many more records. At the same 1832time one can open(2) mappings from the listings of two processes and 1833comparing their inode numbers to figure out which anonymous memory areas 1834are actually shared. 1835 1836------------------------------------------------------------------------------ 1837Configuring procfs 1838------------------------------------------------------------------------------ 1839 18404.1 Mount options 1841--------------------- 1842 1843The following mount options are supported: 1844 1845 hidepid= Set /proc/<pid>/ access mode. 1846 gid= Set the group authorized to learn processes information. 1847 1848hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories 1849(default). 1850 1851hidepid=1 means users may not access any /proc/<pid>/ directories but their 1852own. Sensitive files like cmdline, sched*, status are now protected against 1853other users. This makes it impossible to learn whether any user runs 1854specific program (given the program doesn't reveal itself by its behaviour). 1855As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, 1856poorly written programs passing sensitive information via program arguments are 1857now protected against local eavesdroppers. 1858 1859hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other 1860users. It doesn't mean that it hides a fact whether a process with a specific 1861pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), 1862but it hides process' uid and gid, which may be learned by stat()'ing 1863/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering 1864information about running processes, whether some daemon runs with elevated 1865privileges, whether other user runs some sensitive program, whether other users 1866run any program at all, etc. 1867 1868gid= defines a group authorized to learn processes information otherwise 1869prohibited by hidepid=. If you use some daemon like identd which needs to learn 1870information about processes information, just add identd to this group. 1871