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>
7 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9 ------------------------------------------------------------------------------
10 Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12 ------------------------------------------------------------------------------
13 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
19 0.1 Introduction/Credits
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
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
33 2 Modifying System Parameters
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
37 3.2 /proc/<pid>/oom_score - Display current oom-killer score
38 3.3 /proc/<pid>/io - Display the IO accounting fields
39 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
40 3.5 /proc/<pid>/mountinfo - Information about mounts
41 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
44 ------------------------------------------------------------------------------
46 ------------------------------------------------------------------------------
48 0.1 Introduction/Credits
49 ------------------------
51 This documentation is part of a soon (or so we hope) to be released book on
52 the SuSE Linux distribution. As there is no complete documentation for the
53 /proc file system and we've used many freely available sources to write these
54 chapters, it seems only fair to give the work back to the Linux community.
55 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
56 afraid it's still far from complete, but we hope it will be useful. As far as
57 we know, it is the first 'all-in-one' document about the /proc file system. It
58 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
59 SPARC, AXP, etc., features, you probably won't find what you are looking for.
60 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
61 additions and patches are welcome and will be added to this document if you
64 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
65 other people for help compiling this documentation. We'd also like to extend a
66 special thank you to Andi Kleen for documentation, which we relied on heavily
67 to create this document, as well as the additional information he provided.
68 Thanks to everybody else who contributed source or docs to the Linux kernel
69 and helped create a great piece of software... :)
71 If you have any comments, corrections or additions, please don't hesitate to
72 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
75 The latest version of this document is available online at
76 http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version.
78 If the above direction does not works for you, ypu could try the kernel
79 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
80 comandante@zaralinux.com.
85 We don't guarantee the correctness of this document, and if you come to us
86 complaining about how you screwed up your system because of incorrect
87 documentation, we won't feel responsible...
89 ------------------------------------------------------------------------------
90 CHAPTER 1: COLLECTING SYSTEM INFORMATION
91 ------------------------------------------------------------------------------
93 ------------------------------------------------------------------------------
95 ------------------------------------------------------------------------------
96 * Investigating the properties of the pseudo file system /proc and its
97 ability to provide information on the running Linux system
98 * Examining /proc's structure
99 * Uncovering various information about the kernel and the processes running
101 ------------------------------------------------------------------------------
104 The proc file system acts as an interface to internal data structures in the
105 kernel. It can be used to obtain information about the system and to change
106 certain kernel parameters at runtime (sysctl).
108 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
109 show you how you can use /proc/sys to change settings.
111 1.1 Process-Specific Subdirectories
112 -----------------------------------
114 The directory /proc contains (among other things) one subdirectory for each
115 process running on the system, which is named after the process ID (PID).
117 The link self points to the process reading the file system. Each process
118 subdirectory has the entries listed in Table 1-1.
121 Table 1-1: Process specific entries in /proc
122 ..............................................................................
124 clear_refs Clears page referenced bits shown in smaps output
125 cmdline Command line arguments
126 cpu Current and last cpu in which it was executed (2.4)(smp)
127 cwd Link to the current working directory
128 environ Values of environment variables
129 exe Link to the executable of this process
130 fd Directory, which contains all file descriptors
131 maps Memory maps to executables and library files (2.4)
132 mem Memory held by this process
133 root Link to the root directory of this process
135 statm Process memory status information
136 status Process status in human readable form
137 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
138 stack Report full stack trace, enable via CONFIG_STACKTRACE
139 smaps a extension based on maps, showing the memory consumption of
141 ..............................................................................
143 For example, to get the status information of a process, all you have to do is
144 read the file /proc/PID/status:
146 >cat /proc/self/status
170 SigPnd: 0000000000000000
171 ShdPnd: 0000000000000000
172 SigBlk: 0000000000000000
173 SigIgn: 0000000000000000
174 SigCgt: 0000000000000000
175 CapInh: 00000000fffffeff
176 CapPrm: 0000000000000000
177 CapEff: 0000000000000000
178 CapBnd: ffffffffffffffff
179 voluntary_ctxt_switches: 0
180 nonvoluntary_ctxt_switches: 1
182 This shows you nearly the same information you would get if you viewed it with
183 the ps command. In fact, ps uses the proc file system to obtain its
184 information. But you get a more detailed view of the process by reading the
185 file /proc/PID/status. It fields are described in table 1-2.
187 The statm file contains more detailed information about the process
188 memory usage. Its seven fields are explained in Table 1-3. The stat file
189 contains details information about the process itself. Its fields are
190 explained in Table 1-4.
192 (for SMP CONFIG users)
193 For making accounting scalable, RSS related information are handled in
194 asynchronous manner and the vaule may not be very precise. To see a precise
195 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
196 It's slow but very precise.
198 Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
199 ..............................................................................
201 Name filename of the executable
202 State state (R is running, S is sleeping, D is sleeping
203 in an uninterruptible wait, Z is zombie,
204 T is traced or stopped)
207 PPid process id of the parent process
208 TracerPid PID of process tracing this process (0 if not)
209 Uid Real, effective, saved set, and file system UIDs
210 Gid Real, effective, saved set, and file system GIDs
211 FDSize number of file descriptor slots currently allocated
212 Groups supplementary group list
213 VmPeak peak virtual memory size
214 VmSize total program size
215 VmLck locked memory size
216 VmHWM peak resident set size ("high water mark")
217 VmRSS size of memory portions
218 VmData size of data, stack, and text segments
219 VmStk size of data, stack, and text segments
220 VmExe size of text segment
221 VmLib size of shared library code
222 VmPTE size of page table entries
223 VmSwap size of swap usage (the number of referred swapents)
224 Threads number of threads
225 SigQ number of signals queued/max. number for queue
226 SigPnd bitmap of pending signals for the thread
227 ShdPnd bitmap of shared pending signals for the process
228 SigBlk bitmap of blocked signals
229 SigIgn bitmap of ignored signals
230 SigCgt bitmap of catched signals
231 CapInh bitmap of inheritable capabilities
232 CapPrm bitmap of permitted capabilities
233 CapEff bitmap of effective capabilities
234 CapBnd bitmap of capabilities bounding set
235 Cpus_allowed mask of CPUs on which this process may run
236 Cpus_allowed_list Same as previous, but in "list format"
237 Mems_allowed mask of memory nodes allowed to this process
238 Mems_allowed_list Same as previous, but in "list format"
239 voluntary_ctxt_switches number of voluntary context switches
240 nonvoluntary_ctxt_switches number of non voluntary context switches
241 ..............................................................................
243 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
244 ..............................................................................
246 size total program size (pages) (same as VmSize in status)
247 resident size of memory portions (pages) (same as VmRSS in status)
248 shared number of pages that are shared (i.e. backed by a file)
249 trs number of pages that are 'code' (not including libs; broken,
250 includes data segment)
251 lrs number of pages of library (always 0 on 2.6)
252 drs number of pages of data/stack (including libs; broken,
253 includes library text)
254 dt number of dirty pages (always 0 on 2.6)
255 ..............................................................................
258 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
259 ..............................................................................
262 tcomm filename of the executable
263 state state (R is running, S is sleeping, D is sleeping in an
264 uninterruptible wait, Z is zombie, T is traced or stopped)
265 ppid process id of the parent process
266 pgrp pgrp of the process
268 tty_nr tty the process uses
269 tty_pgrp pgrp of the tty
271 min_flt number of minor faults
272 cmin_flt number of minor faults with child's
273 maj_flt number of major faults
274 cmaj_flt number of major faults with child's
275 utime user mode jiffies
276 stime kernel mode jiffies
277 cutime user mode jiffies with child's
278 cstime kernel mode jiffies with child's
279 priority priority level
281 num_threads number of threads
282 it_real_value (obsolete, always 0)
283 start_time time the process started after system boot
284 vsize virtual memory size
285 rss resident set memory size
286 rsslim current limit in bytes on the rss
287 start_code address above which program text can run
288 end_code address below which program text can run
289 start_stack address of the start of the stack
290 esp current value of ESP
291 eip current value of EIP
292 pending bitmap of pending signals
293 blocked bitmap of blocked signals
294 sigign bitmap of ignored signals
295 sigcatch bitmap of catched signals
296 wchan address where process went to sleep
299 exit_signal signal to send to parent thread on exit
300 task_cpu which CPU the task is scheduled on
301 rt_priority realtime priority
302 policy scheduling policy (man sched_setscheduler)
303 blkio_ticks time spent waiting for block IO
304 gtime guest time of the task in jiffies
305 cgtime guest time of the task children in jiffies
306 ..............................................................................
308 The /proc/PID/map file containing the currently mapped memory regions and
309 their access permissions.
313 address perms offset dev inode pathname
315 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
316 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
317 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
318 a7cb1000-a7cb2000 ---p 00000000 00:00 0
319 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 [threadstack:001ff4b4]
320 a7eb2000-a7eb3000 ---p 00000000 00:00 0
321 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
322 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
323 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
324 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
325 a800b000-a800e000 rw-p 00000000 00:00 0
326 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
327 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
328 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
329 a8024000-a8027000 rw-p 00000000 00:00 0
330 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
331 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
332 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
333 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
334 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
336 where "address" is the address space in the process that it occupies, "perms"
337 is a set of permissions:
343 p = private (copy on write)
345 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
346 "inode" is the inode on that device. 0 indicates that no inode is associated
347 with the memory region, as the case would be with BSS (uninitialized data).
348 The "pathname" shows the name associated file for this mapping. If the mapping
349 is not associated with a file:
351 [heap] = the heap of the program
352 [stack] = the stack of the main process
353 [vdso] = the "virtual dynamic shared object",
354 the kernel system call handler
355 [threadstack:xxxxxxxx] = the stack of the thread, xxxxxxxx is the stack size
357 or if empty, the mapping is anonymous.
360 The /proc/PID/smaps is an extension based on maps, showing the memory
361 consumption for each of the process's mappings. For each of mappings there
362 is a series of lines such as the following:
364 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
377 The first of these lines shows the same information as is displayed for the
378 mapping in /proc/PID/maps. The remaining lines show the size of the mapping,
379 the amount of the mapping that is currently resident in RAM, the "proportional
380 set size” (divide each shared page by the number of processes sharing it), the
381 number of clean and dirty shared pages in the mapping, and the number of clean
382 and dirty private pages in the mapping. The "Referenced" indicates the amount
383 of memory currently marked as referenced or accessed.
385 This file is only present if the CONFIG_MMU kernel configuration option is
388 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
389 bits on both physical and virtual pages associated with a process.
390 To clear the bits for all the pages associated with the process
391 > echo 1 > /proc/PID/clear_refs
393 To clear the bits for the anonymous pages associated with the process
394 > echo 2 > /proc/PID/clear_refs
396 To clear the bits for the file mapped pages associated with the process
397 > echo 3 > /proc/PID/clear_refs
398 Any other value written to /proc/PID/clear_refs will have no effect.
404 Similar to the process entries, the kernel data files give information about
405 the running kernel. The files used to obtain this information are contained in
406 /proc and are listed in Table 1-5. Not all of these will be present in your
407 system. It depends on the kernel configuration and the loaded modules, which
408 files are there, and which are missing.
410 Table 1-5: Kernel info in /proc
411 ..............................................................................
413 apm Advanced power management info
414 buddyinfo Kernel memory allocator information (see text) (2.5)
415 bus Directory containing bus specific information
416 cmdline Kernel command line
417 cpuinfo Info about the CPU
418 devices Available devices (block and character)
419 dma Used DMS channels
420 filesystems Supported filesystems
421 driver Various drivers grouped here, currently rtc (2.4)
422 execdomains Execdomains, related to security (2.4)
423 fb Frame Buffer devices (2.4)
424 fs File system parameters, currently nfs/exports (2.4)
425 ide Directory containing info about the IDE subsystem
426 interrupts Interrupt usage
427 iomem Memory map (2.4)
428 ioports I/O port usage
429 irq Masks for irq to cpu affinity (2.4)(smp?)
430 isapnp ISA PnP (Plug&Play) Info (2.4)
431 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
433 ksyms Kernel symbol table
434 loadavg Load average of last 1, 5 & 15 minutes
438 modules List of loaded modules
439 mounts Mounted filesystems
440 net Networking info (see text)
441 partitions Table of partitions known to the system
442 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
443 decoupled by lspci (2.4)
445 scsi SCSI info (see text)
446 slabinfo Slab pool info
447 softirqs softirq usage
448 stat Overall statistics
449 swaps Swap space utilization
451 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
452 tty Info of tty drivers
454 version Kernel version
455 video bttv info of video resources (2.4)
456 vmallocinfo Show vmalloced areas
457 ..............................................................................
459 You can, for example, check which interrupts are currently in use and what
460 they are used for by looking in the file /proc/interrupts:
462 > cat /proc/interrupts
464 0: 8728810 XT-PIC timer
465 1: 895 XT-PIC keyboard
467 3: 531695 XT-PIC aha152x
468 4: 2014133 XT-PIC serial
469 5: 44401 XT-PIC pcnet_cs
472 12: 182918 XT-PIC PS/2 Mouse
474 14: 1232265 XT-PIC ide0
478 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
479 output of a SMP machine):
481 > cat /proc/interrupts
484 0: 1243498 1214548 IO-APIC-edge timer
485 1: 8949 8958 IO-APIC-edge keyboard
486 2: 0 0 XT-PIC cascade
487 5: 11286 10161 IO-APIC-edge soundblaster
488 8: 1 0 IO-APIC-edge rtc
489 9: 27422 27407 IO-APIC-edge 3c503
490 12: 113645 113873 IO-APIC-edge PS/2 Mouse
492 14: 22491 24012 IO-APIC-edge ide0
493 15: 2183 2415 IO-APIC-edge ide1
494 17: 30564 30414 IO-APIC-level eth0
495 18: 177 164 IO-APIC-level bttv
500 NMI is incremented in this case because every timer interrupt generates a NMI
501 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
503 LOC is the local interrupt counter of the internal APIC of every CPU.
505 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
506 connects the CPUs in a SMP system. This means that an error has been detected,
507 the IO-APIC automatically retry the transmission, so it should not be a big
508 problem, but you should read the SMP-FAQ.
510 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
511 /proc/interrupts to display every IRQ vector in use by the system, not
512 just those considered 'most important'. The new vectors are:
514 THR -- interrupt raised when a machine check threshold counter
515 (typically counting ECC corrected errors of memory or cache) exceeds
516 a configurable threshold. Only available on some systems.
518 TRM -- a thermal event interrupt occurs when a temperature threshold
519 has been exceeded for the CPU. This interrupt may also be generated
520 when the temperature drops back to normal.
522 SPU -- a spurious interrupt is some interrupt that was raised then lowered
523 by some IO device before it could be fully processed by the APIC. Hence
524 the APIC sees the interrupt but does not know what device it came from.
525 For this case the APIC will generate the interrupt with a IRQ vector
526 of 0xff. This might also be generated by chipset bugs.
528 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
529 sent from one CPU to another per the needs of the OS. Typically,
530 their statistics are used by kernel developers and interested users to
531 determine the occurrence of interrupts of the given type.
533 The above IRQ vectors are displayed only when relevent. For example,
534 the threshold vector does not exist on x86_64 platforms. Others are
535 suppressed when the system is a uniprocessor. As of this writing, only
536 i386 and x86_64 platforms support the new IRQ vector displays.
538 Of some interest is the introduction of the /proc/irq directory to 2.4.
539 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
540 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
541 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
546 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
547 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
551 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
552 IRQ, you can set it by doing:
554 > echo 1 > /proc/irq/10/smp_affinity
556 This means that only the first CPU will handle the IRQ, but you can also echo
557 5 which means that only the first and fourth CPU can handle the IRQ.
559 The contents of each smp_affinity file is the same by default:
561 > cat /proc/irq/0/smp_affinity
564 The default_smp_affinity mask applies to all non-active IRQs, which are the
565 IRQs which have not yet been allocated/activated, and hence which lack a
566 /proc/irq/[0-9]* directory.
568 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
569 profiler. Default value is ffffffff (all cpus).
571 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
572 between all the CPUs which are allowed to handle it. As usual the kernel has
573 more info than you and does a better job than you, so the defaults are the
574 best choice for almost everyone.
576 There are three more important subdirectories in /proc: net, scsi, and sys.
577 The general rule is that the contents, or even the existence of these
578 directories, depend on your kernel configuration. If SCSI is not enabled, the
579 directory scsi may not exist. The same is true with the net, which is there
580 only when networking support is present in the running kernel.
582 The slabinfo file gives information about memory usage at the slab level.
583 Linux uses slab pools for memory management above page level in version 2.2.
584 Commonly used objects have their own slab pool (such as network buffers,
585 directory cache, and so on).
587 ..............................................................................
589 > cat /proc/buddyinfo
591 Node 0, zone DMA 0 4 5 4 4 3 ...
592 Node 0, zone Normal 1 0 0 1 101 8 ...
593 Node 0, zone HighMem 2 0 0 1 1 0 ...
595 Memory fragmentation is a problem under some workloads, and buddyinfo is a
596 useful tool for helping diagnose these problems. Buddyinfo will give you a
597 clue as to how big an area you can safely allocate, or why a previous
600 Each column represents the number of pages of a certain order which are
601 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
602 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
603 available in ZONE_NORMAL, etc...
605 ..............................................................................
609 Provides information about distribution and utilization of memory. This
610 varies by architecture and compile options. The following is from a
611 16GB PIII, which has highmem enabled. You may not have all of these fields.
616 MemTotal: 16344972 kB
623 HighTotal: 15597528 kB
624 HighFree: 13629632 kB
634 SReclaimable: 159856 kB
635 SUnreclaim: 124508 kB
640 CommitLimit: 7669796 kB
641 Committed_AS: 100056 kB
642 VmallocTotal: 112216 kB
644 VmallocChunk: 111088 kB
646 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
647 bits and the kernel binary code)
648 MemFree: The sum of LowFree+HighFree
649 Buffers: Relatively temporary storage for raw disk blocks
650 shouldn't get tremendously large (20MB or so)
651 Cached: in-memory cache for files read from the disk (the
652 pagecache). Doesn't include SwapCached
653 SwapCached: Memory that once was swapped out, is swapped back in but
654 still also is in the swapfile (if memory is needed it
655 doesn't need to be swapped out AGAIN because it is already
656 in the swapfile. This saves I/O)
657 Active: Memory that has been used more recently and usually not
658 reclaimed unless absolutely necessary.
659 Inactive: Memory which has been less recently used. It is more
660 eligible to be reclaimed for other purposes
662 HighFree: Highmem is all memory above ~860MB of physical memory
663 Highmem areas are for use by userspace programs, or
664 for the pagecache. The kernel must use tricks to access
665 this memory, making it slower to access than lowmem.
667 LowFree: Lowmem is memory which can be used for everything that
668 highmem can be used for, but it is also available for the
669 kernel's use for its own data structures. Among many
670 other things, it is where everything from the Slab is
671 allocated. Bad things happen when you're out of lowmem.
672 SwapTotal: total amount of swap space available
673 SwapFree: Memory which has been evicted from RAM, and is temporarily
675 Dirty: Memory which is waiting to get written back to the disk
676 Writeback: Memory which is actively being written back to the disk
677 AnonPages: Non-file backed pages mapped into userspace page tables
678 Mapped: files which have been mmaped, such as libraries
679 Slab: in-kernel data structures cache
680 SReclaimable: Part of Slab, that might be reclaimed, such as caches
681 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
682 PageTables: amount of memory dedicated to the lowest level of page
684 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
686 Bounce: Memory used for block device "bounce buffers"
687 WritebackTmp: Memory used by FUSE for temporary writeback buffers
688 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
689 this is the total amount of memory currently available to
690 be allocated on the system. This limit is only adhered to
691 if strict overcommit accounting is enabled (mode 2 in
692 'vm.overcommit_memory').
693 The CommitLimit is calculated with the following formula:
694 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
695 For example, on a system with 1G of physical RAM and 7G
696 of swap with a `vm.overcommit_ratio` of 30 it would
697 yield a CommitLimit of 7.3G.
698 For more details, see the memory overcommit documentation
699 in vm/overcommit-accounting.
700 Committed_AS: The amount of memory presently allocated on the system.
701 The committed memory is a sum of all of the memory which
702 has been allocated by processes, even if it has not been
703 "used" by them as of yet. A process which malloc()'s 1G
704 of memory, but only touches 300M of it will only show up
705 as using 300M of memory even if it has the address space
706 allocated for the entire 1G. This 1G is memory which has
707 been "committed" to by the VM and can be used at any time
708 by the allocating application. With strict overcommit
709 enabled on the system (mode 2 in 'vm.overcommit_memory'),
710 allocations which would exceed the CommitLimit (detailed
711 above) will not be permitted. This is useful if one needs
712 to guarantee that processes will not fail due to lack of
713 memory once that memory has been successfully allocated.
714 VmallocTotal: total size of vmalloc memory area
715 VmallocUsed: amount of vmalloc area which is used
716 VmallocChunk: largest contiguous block of vmalloc area which is free
718 ..............................................................................
722 Provides information about vmalloced/vmaped areas. One line per area,
723 containing the virtual address range of the area, size in bytes,
724 caller information of the creator, and optional information depending
725 on the kind of area :
727 pages=nr number of pages
728 phys=addr if a physical address was specified
729 ioremap I/O mapping (ioremap() and friends)
730 vmalloc vmalloc() area
733 vpages buffer for pages pointers was vmalloced (huge area)
734 N<node>=nr (Only on NUMA kernels)
735 Number of pages allocated on memory node <node>
737 > cat /proc/vmallocinfo
738 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
739 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
740 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
741 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
742 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
743 phys=7fee8000 ioremap
744 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
745 phys=7fee7000 ioremap
746 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
747 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
748 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
749 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
751 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
752 /0x130 [x_tables] pages=4 vmalloc N0=4
753 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
754 pages=14 vmalloc N2=14
755 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
757 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
759 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
760 pages=10 vmalloc N0=10
762 ..............................................................................
766 Provides counts of softirq handlers serviced since boot time, for each cpu.
771 TIMER: 27166 27120 27097 27034
776 SCHED: 27035 26983 26971 26746
778 RCU: 1678 1769 2178 2250
781 1.3 IDE devices in /proc/ide
782 ----------------------------
784 The subdirectory /proc/ide contains information about all IDE devices of which
785 the kernel is aware. There is one subdirectory for each IDE controller, the
786 file drivers and a link for each IDE device, pointing to the device directory
787 in the controller specific subtree.
789 The file drivers contains general information about the drivers used for the
792 > cat /proc/ide/drivers
793 ide-cdrom version 4.53
794 ide-disk version 1.08
796 More detailed information can be found in the controller specific
797 subdirectories. These are named ide0, ide1 and so on. Each of these
798 directories contains the files shown in table 1-6.
801 Table 1-6: IDE controller info in /proc/ide/ide?
802 ..............................................................................
804 channel IDE channel (0 or 1)
805 config Configuration (only for PCI/IDE bridge)
807 model Type/Chipset of IDE controller
808 ..............................................................................
810 Each device connected to a controller has a separate subdirectory in the
811 controllers directory. The files listed in table 1-7 are contained in these
815 Table 1-7: IDE device information
816 ..............................................................................
819 capacity Capacity of the medium (in 512Byte blocks)
820 driver driver and version
821 geometry physical and logical geometry
822 identify device identify block
824 model device identifier
825 settings device setup
826 smart_thresholds IDE disk management thresholds
827 smart_values IDE disk management values
828 ..............................................................................
830 The most interesting file is settings. This file contains a nice overview of
831 the drive parameters:
833 # cat /proc/ide/ide0/hda/settings
834 name value min max mode
835 ---- ----- --- --- ----
836 bios_cyl 526 0 65535 rw
837 bios_head 255 0 255 rw
839 breada_readahead 4 0 127 rw
841 file_readahead 72 0 2097151 rw
843 keepsettings 0 0 1 rw
844 max_kb_per_request 122 1 127 rw
848 pio_mode write-only 0 255 w
854 1.4 Networking info in /proc/net
855 --------------------------------
857 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
858 additional values you get for IP version 6 if you configure the kernel to
859 support this. Table 1-9 lists the files and their meaning.
862 Table 1-8: IPv6 info in /proc/net
863 ..............................................................................
865 udp6 UDP sockets (IPv6)
866 tcp6 TCP sockets (IPv6)
867 raw6 Raw device statistics (IPv6)
868 igmp6 IP multicast addresses, which this host joined (IPv6)
869 if_inet6 List of IPv6 interface addresses
870 ipv6_route Kernel routing table for IPv6
871 rt6_stats Global IPv6 routing tables statistics
872 sockstat6 Socket statistics (IPv6)
873 snmp6 Snmp data (IPv6)
874 ..............................................................................
877 Table 1-9: Network info in /proc/net
878 ..............................................................................
881 dev network devices with statistics
882 dev_mcast the Layer2 multicast groups a device is listening too
883 (interface index, label, number of references, number of bound
885 dev_stat network device status
886 ip_fwchains Firewall chain linkage
887 ip_fwnames Firewall chain names
888 ip_masq Directory containing the masquerading tables
889 ip_masquerade Major masquerading table
890 netstat Network statistics
891 raw raw device statistics
892 route Kernel routing table
893 rpc Directory containing rpc info
894 rt_cache Routing cache
896 sockstat Socket statistics
898 tr_rif Token ring RIF routing table
900 unix UNIX domain sockets
901 wireless Wireless interface data (Wavelan etc)
902 igmp IP multicast addresses, which this host joined
903 psched Global packet scheduler parameters.
904 netlink List of PF_NETLINK sockets
905 ip_mr_vifs List of multicast virtual interfaces
906 ip_mr_cache List of multicast routing cache
907 ..............................................................................
909 You can use this information to see which network devices are available in
910 your system and how much traffic was routed over those devices:
914 face |bytes packets errs drop fifo frame compressed multicast|[...
915 lo: 908188 5596 0 0 0 0 0 0 [...
916 ppp0:15475140 20721 410 0 0 410 0 0 [...
917 eth0: 614530 7085 0 0 0 0 0 1 [...
920 ...] bytes packets errs drop fifo colls carrier compressed
921 ...] 908188 5596 0 0 0 0 0 0
922 ...] 1375103 17405 0 0 0 0 0 0
923 ...] 1703981 5535 0 0 0 3 0 0
925 In addition, each Channel Bond interface has it's own directory. For
926 example, the bond0 device will have a directory called /proc/net/bond0/.
927 It will contain information that is specific to that bond, such as the
928 current slaves of the bond, the link status of the slaves, and how
929 many times the slaves link has failed.
934 If you have a SCSI host adapter in your system, you'll find a subdirectory
935 named after the driver for this adapter in /proc/scsi. You'll also see a list
936 of all recognized SCSI devices in /proc/scsi:
940 Host: scsi0 Channel: 00 Id: 00 Lun: 00
941 Vendor: IBM Model: DGHS09U Rev: 03E0
942 Type: Direct-Access ANSI SCSI revision: 03
943 Host: scsi0 Channel: 00 Id: 06 Lun: 00
944 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
945 Type: CD-ROM ANSI SCSI revision: 02
948 The directory named after the driver has one file for each adapter found in
949 the system. These files contain information about the controller, including
950 the used IRQ and the IO address range. The amount of information shown is
951 dependent on the adapter you use. The example shows the output for an Adaptec
952 AHA-2940 SCSI adapter:
954 > cat /proc/scsi/aic7xxx/0
956 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
958 TCQ Enabled By Default : Disabled
959 AIC7XXX_PROC_STATS : Disabled
960 AIC7XXX_RESET_DELAY : 5
961 Adapter Configuration:
962 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
963 Ultra Wide Controller
964 PCI MMAPed I/O Base: 0xeb001000
965 Adapter SEEPROM Config: SEEPROM found and used.
966 Adaptec SCSI BIOS: Enabled
968 SCBs: Active 0, Max Active 2,
969 Allocated 15, HW 16, Page 255
971 BIOS Control Word: 0x18b6
972 Adapter Control Word: 0x005b
973 Extended Translation: Enabled
974 Disconnect Enable Flags: 0xffff
975 Ultra Enable Flags: 0x0001
976 Tag Queue Enable Flags: 0x0000
977 Ordered Queue Tag Flags: 0x0000
978 Default Tag Queue Depth: 8
979 Tagged Queue By Device array for aic7xxx host instance 0:
980 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
981 Actual queue depth per device for aic7xxx host instance 0:
982 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
985 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
986 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
987 Total transfers 160151 (74577 reads and 85574 writes)
989 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
990 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
991 Total transfers 0 (0 reads and 0 writes)
994 1.6 Parallel port info in /proc/parport
995 ---------------------------------------
997 The directory /proc/parport contains information about the parallel ports of
998 your system. It has one subdirectory for each port, named after the port
1001 These directories contain the four files shown in Table 1-10.
1004 Table 1-10: Files in /proc/parport
1005 ..............................................................................
1007 autoprobe Any IEEE-1284 device ID information that has been acquired.
1008 devices list of the device drivers using that port. A + will appear by the
1009 name of the device currently using the port (it might not appear
1011 hardware Parallel port's base address, IRQ line and DMA channel.
1012 irq IRQ that parport is using for that port. This is in a separate
1013 file to allow you to alter it by writing a new value in (IRQ
1015 ..............................................................................
1017 1.7 TTY info in /proc/tty
1018 -------------------------
1020 Information about the available and actually used tty's can be found in the
1021 directory /proc/tty.You'll find entries for drivers and line disciplines in
1022 this directory, as shown in Table 1-11.
1025 Table 1-11: Files in /proc/tty
1026 ..............................................................................
1028 drivers list of drivers and their usage
1029 ldiscs registered line disciplines
1030 driver/serial usage statistic and status of single tty lines
1031 ..............................................................................
1033 To see which tty's are currently in use, you can simply look into the file
1036 > cat /proc/tty/drivers
1037 pty_slave /dev/pts 136 0-255 pty:slave
1038 pty_master /dev/ptm 128 0-255 pty:master
1039 pty_slave /dev/ttyp 3 0-255 pty:slave
1040 pty_master /dev/pty 2 0-255 pty:master
1041 serial /dev/cua 5 64-67 serial:callout
1042 serial /dev/ttyS 4 64-67 serial
1043 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1044 /dev/ptmx /dev/ptmx 5 2 system
1045 /dev/console /dev/console 5 1 system:console
1046 /dev/tty /dev/tty 5 0 system:/dev/tty
1047 unknown /dev/tty 4 1-63 console
1050 1.8 Miscellaneous kernel statistics in /proc/stat
1051 -------------------------------------------------
1053 Various pieces of information about kernel activity are available in the
1054 /proc/stat file. All of the numbers reported in this file are aggregates
1055 since the system first booted. For a quick look, simply cat the file:
1058 cpu 2255 34 2290 22625563 6290 127 456 0 0
1059 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1060 cpu1 1123 0 849 11313845 2614 0 18 0 0
1061 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1067 softirq 183433 0 21755 12 39 1137 231 21459 2263
1069 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1070 lines. These numbers identify the amount of time the CPU has spent performing
1071 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1072 second). The meanings of the columns are as follows, from left to right:
1074 - user: normal processes executing in user mode
1075 - nice: niced processes executing in user mode
1076 - system: processes executing in kernel mode
1077 - idle: twiddling thumbs
1078 - iowait: waiting for I/O to complete
1079 - irq: servicing interrupts
1080 - softirq: servicing softirqs
1081 - steal: involuntary wait
1082 - guest: running a normal guest
1083 - guest_nice: running a niced guest
1085 The "intr" line gives counts of interrupts serviced since boot time, for each
1086 of the possible system interrupts. The first column is the total of all
1087 interrupts serviced; each subsequent column is the total for that particular
1090 The "ctxt" line gives the total number of context switches across all CPUs.
1092 The "btime" line gives the time at which the system booted, in seconds since
1095 The "processes" line gives the number of processes and threads created, which
1096 includes (but is not limited to) those created by calls to the fork() and
1097 clone() system calls.
1099 The "procs_running" line gives the total number of threads that are
1100 running or ready to run (i.e., the total number of runnable threads).
1102 The "procs_blocked" line gives the number of processes currently blocked,
1103 waiting for I/O to complete.
1105 The "softirq" line gives counts of softirqs serviced since boot time, for each
1106 of the possible system softirqs. The first column is the total of all
1107 softirqs serviced; each subsequent column is the total for that particular
1111 1.9 Ext4 file system parameters
1112 ------------------------------
1114 Information about mounted ext4 file systems can be found in
1115 /proc/fs/ext4. Each mounted filesystem will have a directory in
1116 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1117 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1118 in Table 1-12, below.
1120 Table 1-12: Files in /proc/fs/ext4/<devname>
1121 ..............................................................................
1123 mb_groups details of multiblock allocator buddy cache of free blocks
1124 ..............................................................................
1127 ------------------------------------------------------------------------------
1129 ------------------------------------------------------------------------------
1130 The /proc file system serves information about the running system. It not only
1131 allows access to process data but also allows you to request the kernel status
1132 by reading files in the hierarchy.
1134 The directory structure of /proc reflects the types of information and makes
1135 it easy, if not obvious, where to look for specific data.
1136 ------------------------------------------------------------------------------
1138 ------------------------------------------------------------------------------
1139 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1140 ------------------------------------------------------------------------------
1142 ------------------------------------------------------------------------------
1144 ------------------------------------------------------------------------------
1145 * Modifying kernel parameters by writing into files found in /proc/sys
1146 * Exploring the files which modify certain parameters
1147 * Review of the /proc/sys file tree
1148 ------------------------------------------------------------------------------
1151 A very interesting part of /proc is the directory /proc/sys. This is not only
1152 a source of information, it also allows you to change parameters within the
1153 kernel. Be very careful when attempting this. You can optimize your system,
1154 but you can also cause it to crash. Never alter kernel parameters on a
1155 production system. Set up a development machine and test to make sure that
1156 everything works the way you want it to. You may have no alternative but to
1157 reboot the machine once an error has been made.
1159 To change a value, simply echo the new value into the file. An example is
1160 given below in the section on the file system data. You need to be root to do
1161 this. You can create your own boot script to perform this every time your
1164 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1165 general things in the operation of the Linux kernel. Since some of the files
1166 can inadvertently disrupt your system, it is advisable to read both
1167 documentation and source before actually making adjustments. In any case, be
1168 very careful when writing to any of these files. The entries in /proc may
1169 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1170 review the kernel documentation in the directory /usr/src/linux/Documentation.
1171 This chapter is heavily based on the documentation included in the pre 2.2
1172 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1174 Please see: Documentation/sysctls/ directory for descriptions of these
1177 ------------------------------------------------------------------------------
1179 ------------------------------------------------------------------------------
1180 Certain aspects of kernel behavior can be modified at runtime, without the
1181 need to recompile the kernel, or even to reboot the system. The files in the
1182 /proc/sys tree can not only be read, but also modified. You can use the echo
1183 command to write value into these files, thereby changing the default settings
1185 ------------------------------------------------------------------------------
1187 ------------------------------------------------------------------------------
1188 CHAPTER 3: PER-PROCESS PARAMETERS
1189 ------------------------------------------------------------------------------
1191 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score
1192 ------------------------------------------------------
1194 This file can be used to adjust the score used to select which processes
1195 should be killed in an out-of-memory situation. Giving it a high score will
1196 increase the likelihood of this process being killed by the oom-killer. Valid
1197 values are in the range -16 to +15, plus the special value -17, which disables
1198 oom-killing altogether for this process.
1200 The process to be killed in an out-of-memory situation is selected among all others
1201 based on its badness score. This value equals the original memory size of the process
1202 and is then updated according to its CPU time (utime + stime) and the
1203 run time (uptime - start time). The longer it runs the smaller is the score.
1204 Badness score is divided by the square root of the CPU time and then by
1205 the double square root of the run time.
1207 Swapped out tasks are killed first. Half of each child's memory size is added to
1208 the parent's score if they do not share the same memory. Thus forking servers
1209 are the prime candidates to be killed. Having only one 'hungry' child will make
1210 parent less preferable than the child.
1212 /proc/<pid>/oom_score shows process' current badness score.
1214 The following heuristics are then applied:
1215 * if the task was reniced, its score doubles
1216 * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE
1217 or CAP_SYS_RAWIO) have their score divided by 4
1218 * if oom condition happened in one cpuset and checked process does not belong
1219 to it, its score is divided by 8
1220 * the resulting score is multiplied by two to the power of oom_adj, i.e.
1221 points <<= oom_adj when it is positive and
1222 points >>= -(oom_adj) otherwise
1224 The task with the highest badness score is then selected and its children
1225 are killed, process itself will be killed in an OOM situation when it does
1226 not have children or some of them disabled oom like described above.
1228 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1229 -------------------------------------------------------------
1231 This file can be used to check the current score used by the oom-killer is for
1232 any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
1233 process should be killed in an out-of-memory situation.
1236 3.3 /proc/<pid>/io - Display the IO accounting fields
1237 -------------------------------------------------------
1239 This file contains IO statistics for each running process
1244 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1247 test:/tmp # cat /proc/3828/io
1253 write_bytes: 323932160
1254 cancelled_write_bytes: 0
1263 I/O counter: chars read
1264 The number of bytes which this task has caused to be read from storage. This
1265 is simply the sum of bytes which this process passed to read() and pread().
1266 It includes things like tty IO and it is unaffected by whether or not actual
1267 physical disk IO was required (the read might have been satisfied from
1274 I/O counter: chars written
1275 The number of bytes which this task has caused, or shall cause to be written
1276 to disk. Similar caveats apply here as with rchar.
1282 I/O counter: read syscalls
1283 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1290 I/O counter: write syscalls
1291 Attempt to count the number of write I/O operations, i.e. syscalls like
1292 write() and pwrite().
1298 I/O counter: bytes read
1299 Attempt to count the number of bytes which this process really did cause to
1300 be fetched from the storage layer. Done at the submit_bio() level, so it is
1301 accurate for block-backed filesystems. <please add status regarding NFS and
1302 CIFS at a later time>
1308 I/O counter: bytes written
1309 Attempt to count the number of bytes which this process caused to be sent to
1310 the storage layer. This is done at page-dirtying time.
1313 cancelled_write_bytes
1314 ---------------------
1316 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1317 then deletes the file, it will in fact perform no writeout. But it will have
1318 been accounted as having caused 1MB of write.
1319 In other words: The number of bytes which this process caused to not happen,
1320 by truncating pagecache. A task can cause "negative" IO too. If this task
1321 truncates some dirty pagecache, some IO which another task has been accounted
1322 for (in it's write_bytes) will not be happening. We _could_ just subtract that
1323 from the truncating task's write_bytes, but there is information loss in doing
1330 At its current implementation state, this is a bit racy on 32-bit machines: if
1331 process A reads process B's /proc/pid/io while process B is updating one of
1332 those 64-bit counters, process A could see an intermediate result.
1335 More information about this can be found within the taskstats documentation in
1336 Documentation/accounting.
1338 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1339 ---------------------------------------------------------------
1340 When a process is dumped, all anonymous memory is written to a core file as
1341 long as the size of the core file isn't limited. But sometimes we don't want
1342 to dump some memory segments, for example, huge shared memory. Conversely,
1343 sometimes we want to save file-backed memory segments into a core file, not
1344 only the individual files.
1346 /proc/<pid>/coredump_filter allows you to customize which memory segments
1347 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1348 of memory types. If a bit of the bitmask is set, memory segments of the
1349 corresponding memory type are dumped, otherwise they are not dumped.
1351 The following 7 memory types are supported:
1352 - (bit 0) anonymous private memory
1353 - (bit 1) anonymous shared memory
1354 - (bit 2) file-backed private memory
1355 - (bit 3) file-backed shared memory
1356 - (bit 4) ELF header pages in file-backed private memory areas (it is
1357 effective only if the bit 2 is cleared)
1358 - (bit 5) hugetlb private memory
1359 - (bit 6) hugetlb shared memory
1361 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1362 are always dumped regardless of the bitmask status.
1364 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1365 effected by bit 5-6.
1367 Default value of coredump_filter is 0x23; this means all anonymous memory
1368 segments and hugetlb private memory are dumped.
1370 If you don't want to dump all shared memory segments attached to pid 1234,
1371 write 0x21 to the process's proc file.
1373 $ echo 0x21 > /proc/1234/coredump_filter
1375 When a new process is created, the process inherits the bitmask status from its
1376 parent. It is useful to set up coredump_filter before the program runs.
1379 $ echo 0x7 > /proc/self/coredump_filter
1382 3.5 /proc/<pid>/mountinfo - Information about mounts
1383 --------------------------------------------------------
1385 This file contains lines of the form:
1387 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1388 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1390 (1) mount ID: unique identifier of the mount (may be reused after umount)
1391 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1392 (3) major:minor: value of st_dev for files on filesystem
1393 (4) root: root of the mount within the filesystem
1394 (5) mount point: mount point relative to the process's root
1395 (6) mount options: per mount options
1396 (7) optional fields: zero or more fields of the form "tag[:value]"
1397 (8) separator: marks the end of the optional fields
1398 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1399 (10) mount source: filesystem specific information or "none"
1400 (11) super options: per super block options
1402 Parsers should ignore all unrecognised optional fields. Currently the
1403 possible optional fields are:
1405 shared:X mount is shared in peer group X
1406 master:X mount is slave to peer group X
1407 propagate_from:X mount is slave and receives propagation from peer group X (*)
1408 unbindable mount is unbindable
1410 (*) X is the closest dominant peer group under the process's root. If
1411 X is the immediate master of the mount, or if there's no dominant peer
1412 group under the same root, then only the "master:X" field is present
1413 and not the "propagate_from:X" field.
1415 For more information on mount propagation see:
1417 Documentation/filesystems/sharedsubtree.txt
1420 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1421 --------------------------------------------------------
1422 These files provide a method to access a tasks comm value. It also allows for
1423 a task to set its own or one of its thread siblings comm value. The comm value
1424 is limited in size compared to the cmdline value, so writing anything longer
1425 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob