proc (5)


       proc - process information pseudo-filesystem


       /proc  is  a  pseudo-filesystem which is used as an interface to kernel
       data structures rather than reading and interpreting  /dev/kmem.   Most
       of  it  is  read-only,  but  some  files  allow  kernel variables to be

       The following outline gives a quick tour through the /proc hierarchy.

              There is a numerical subdirectory for each running process;  the
              subdirectory is named by the process ID.  Each contains the fol-
              lowing pseudo-files and directories.

                     This holds the complete command  line  for  the  process,
                     unless  the whole process has been swapped out, or unless
                     the process is a zombie.  In either of these later cases,
                     there  is  nothing in this file: i.e. a read on this file
                     will return 0 characters.   The  command  line  arguments
                     appear  in  this file as a set of null-separated strings,
                     with a further null byte after the last string.

              cwd    This is a link to the current working  directory  of  the
                     process.   To  find  out  the  cwd  of  process  20,  for
                     instance, you can do this:

                     cd /proc/20/cwd; /bin/pwd

                     Note that the pwd command is often a shell  builtin,  and
                     might not work properly. In bash, you may use pwd -P.

                     This  file contains the environment for the process.  The
                     entries are separated by null characters, and  there  may
                     be  a  null character at the end.  Thus, to print out the
                     environment of process 1, you would do:

                     (cat /proc/1/environ; echo) | tr "\000" "\n"

                     (For a reason  why  one  should  want  to  do  this,  see

              exe    Under Linux 2.2 and 2.4 exe is a symbolic link containing
                     the actual path name of the executed  command.   The  exe
                     symbolic  link  can be dereferenced normally - attempting
                     to open exe will open the executable.  You can even  type
                     /proc/[number]/exe  to  run another copy of the same pro-
                     cess as [number].

                     Under Linux 2.0 and earlier  exe  is  a  pointer  to  the

                     find(1)  with  the -inum option can be used to locate the

              fd     This is a subdirectory containing one entry for each file
                     which the process has open, named by its file descriptor,
                     and which is a symbolic link to the actual file  (as  the
                     exe  entry  does).  Thus, 0 is standard input, 1 standard
                     output, 2 standard error, etc.

                     Programs that will take a filename, but will not take the
                     standard  input,  and which write to a file, but will not
                     send their output to standard output, can be  effectively
                     foiled this way, assuming that -i is the flag designating
                     an input file and -o is the flag  designating  an  output
                     foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...
                     and  you  have a working filter.  Note that this will not
                     work for programs that seek on their files, as the  files
                     in the fd directory are not seekable.

                     /proc/self/fd/N is approximately the same as /dev/fd/N in
                     some UNIX and  UNIX-like  systems.   Most  Linux  MAKEDEV
                     scripts  symbolically  link  /dev/fd to /proc/self/fd, in

              maps   A file containing the currently mapped memory regions and
                     their access permissions.

                     The format is:

        address           perms offset  dev   inode      pathname
        08048000-08056000 r-xp 00000000 03:0c 64593      /usr/sbin/gpm
        08056000-08058000 rw-p 0000d000 03:0c 64593      /usr/sbin/gpm
        08058000-0805b000 rwxp 00000000 00:00 0
        40000000-40013000 r-xp 00000000 03:0c 4165       /lib/
        40013000-40015000 rw-p 00012000 03:0c 4165       /lib/
        4001f000-40135000 r-xp 00000000 03:0c 45494      /lib/
        40135000-4013e000 rw-p 00115000 03:0c 45494      /lib/
        4013e000-40142000 rw-p 00000000 00:00 0
        bffff000-c0000000 rwxp 00000000 00:00 0

                     where address is the address space in the process that it
                     occupies, perms is a set of permissions:

                          r = read
                          w = write
                          x = execute
                          s = shared
                          p = private (copy on write)

                     offset is the offset into the file/whatever, dev  is  the
                     device  (major:minor),  and  inode  is  the inode on that
                     device.  0 indicates that no inode is associated with the
                     memory region, as the case would be with bss.

                     Under Linux 2.0 there is no field giving pathname.

              stat   Status  information  about  the process.  This is used by
                     ps(1).  It is defined in  /usr/src/linux/fs/proc/array.c.

                     The  fields,  in order, with their proper scanf(3) format
                     specifiers, are:

                      pid %d The process id.

                     comm %s
                             The filename of the executable,  in  parentheses.
                             This  is visible whether or not the executable is
                             swapped out.

                     state %c
                             One character from the string "RSDZTW" where R is
                             running,  S is sleeping in an interruptible wait,
                             D is waiting in uninterruptible disk sleep, Z  is
                             zombie, T is traced or stopped (on a signal), and
                             W is paging.

                     ppid %d
                             The PID of the parent.

                     pgrp %d
                             The process group ID of the process.

                     session %d
                             The session ID of the process.

                     tty_nr %d
                             The tty the process uses.

                     tpgid %d
                             The process group ID of the  process  which  cur-
                             rently owns the tty that the process is connected

                     flags %lu
                             The flags of the process.  The math bit is  deci-
                             mal 4, and the traced bit is decimal 10.

                     minflt %lu
                             The  number  of minor faults the process has made
                             which have not required  loading  a  memory  page
                             from disk.

                     cminflt %lu
                             The  number  of minor faults that the process and
                             its children have made.

                     majflt %lu
                             The number of major faults the process  has  made
                             which  have  required  loading a memory page from

                     cmajflt %lu
                             The number of major faults that the  process  and

                     cutime %ld
                             The  number  of jiffies that this process and its
                             children have been scheduled in user mode.

                     cstime %ld
                             The number of jiffies that this process  and  its
                             children have been scheduled in kernel mode.

                     priority %ld
                             The standard nice value, plus fifteen.  The value
                             is never negative in the kernel.

                     nice %ld
                             The nice value ranges from  19  (nicest)  to  -19
                             (not nice to others).

                      0 %ld  This  value  is  hard coded to 0 as a placeholder
                             for a removed field.

                     itrealvalue %ld
                             The time in jiffies before the  next  SIGALRM  is
                             sent to the process due to an interval timer.

                     starttime %lu
                             The  time  in  jiffies  the process started after
                             system boot.

                     vsize %lu
                             Virtual memory size in bytes.

                     rss %ld
                             Resident Set Size: number of  pages  the  process
                             has  in  real  memory, minus 3 for administrative
                             purposes. This is  just  the  pages  which  count
                             towards  text,  data,  or stack space.  This does
                             not include pages which  have  not  been  demand-
                             loaded in, or which are swapped out.

                     rlim %lu
                             Current  limit in bytes on the rss of the process
                             (usually 4,294,967,295).

                     startcode %lu
                             The address above which program text can run.

                     endcode %lu
                             The address below which program text can run.

                     startstack %lu
                             The address of the start of the stack.

                     kstkesp %lu
                             The current value  of  esp  (stack  pointer),  as
                             found in the kernel stack page for the process.

                     kstkeip %lu
                     sigignore %lu
                             The bitmap of ignored signals.

                     sigcatch %lu
                             The bitmap of catched signals.

                     wchan %lu
                             This is the "channel" in  which  the  process  is
                             waiting.  It is the address of a system call, and
                             can be looked up in a namelist if you need a tex-
                             tual   name.    (If   you   have   an  up-to-date
                             /etc/psdatabase, then try ps -l to see the  WCHAN
                             field in action.)

                     nswap %lu
                             Number of pages swapped - not maintained.

                     cnswap %lu
                             Cumulative nswap for child processes.

                     exit_signal %d
                             Signal to be sent to parent when we die.

                     processor %d
                             Processor number last executed on.

              statm  Provides  information  about memory status in pages.  The
                     columns are:
                      size       total program size
                      resident   resident set size
                      share      shared pages
                      trs        text (code)
                      drs        data/stack
                      lrs        library
                      dt         dirty pages

              status Provides much of the information in stat and statm in  an
                     format that's easier for humans to parse.

       bus    Contains subdirectories for installed busses.

              pci    Contains various bus subdirectories and pseudo-files con-
                     taining information about pci busses, installed  devices,
                     and device drivers.  Some of these files are not ASCII.

                             Information  about  pci  devices.   They  may  be
                             accessed through lspci(8) and setpci(8).

              Argments passed to the Linux kernel at boot  time.   Often  done
              via a boot manager such as lilo(1).

              This  is  a  collection of CPU and system architecture dependent
              items, for each supported architecture a  different  list.   Two
              common   entries  are  processor  which  gives  CPU  number  and

       driver Empty subdirectory.

              List of the execution domains (ABI personalities).

       fb     Frame buffer information when CONFIG_FB is defined during kernel

              A text listing of the filesystems which were compiled  into  the
              kernel.  Incidentally, this is used by mount(1) to cycle through
              different filesystems when none is specified.

       ide    ide exists on systems with the ide bus.  There  are  directories
              for each ide channel and attached device.  Files include:

              cache              buffer size in KB
              capacity           number of sectors
              driver             driver version
              geometry           physical and logical geometry
              identify           in hexidecimal
              media              media type
              model              manufacturer's model number
              settings           drive settings
              smart_thresholds   in hexidecimal
              smart_values       in hexidecimal

              The  hdparm(8)  utility provides access to this information in a
              friendly format.

              This is used to record the number of interrupts per each IRQ  on
              (at least) the i386 architechure.  Very easy to read formatting,
              done in ASCII.

       iomem  I/O memory map in Linux 2.4.

              This is a list of currently registered Input-Output port regions
              that are in use.

       kcore  This  file  represents  the physical memory of the system and is
              stored in the ELF core file format.  With this pseudo-file,  and
              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
              used to examine the current state of any kernel data structures.

              The  total  length  of  the  file is the size of physical memory
              (RAM) plus 4KB.

       kmsg   This file can be used instead of the syslog(2)  system  call  to
              read  kernel log messages.  A process must have superuser privi-
              leges to read this file, and only one process should make use of
              this facility or syslog(2) to read this file.

              Information in this file is retrieved with the dmesg(8) program.

       locks  This  file  shows current file locks (flock(2) and fcntl(2)) and
              leases (fcntl(2)).

       malloc This file is only present if CONFIGDEBUGMALLOC was defined  dur-
              ing compilation.

              This  is  used  by free(1) to report the amount of free and used
              memory (both physical and swap) on the system  as  well  as  the
              shared memory and buffers used by the kernel.

              It is in the same format as free(1), except in bytes rather than

       mounts This is a list of all the file systems currently mounted on  the
              system.  The format of this file is documented in fstab(5).

              A  text list of the modules that have been loaded by the system.
              See also lsmod(8).

       mtrr   Memory  Type  Range  Registers.   See  /usr/src/linux/Documenta-
              tion/mtrr.txt for details.

       net    various  net  pseudo-files, all of which give the status of some
              part of the networking layer.  These files contain ASCII  struc-
              tures and are, therefore, readable with cat.  However, the stan-
              dard netstat(8) suite provides  much  cleaner  access  to  these

              arp    This holds an ASCII readable dump of the kernel ARP table
                     used for address resolutions. It will show  both  dynami-
                     cally learned and pre-programmed ARP entries.  The format

        IP address     HW type   Flags     HW address          Mask   Device   0x1       0x2       00:50:BF:25:68:F3   *      eth0  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here 'IP address' is the IPv4 address of the machine and the 'HW
              type'  is  the  hardware  type  of the address from RFC 826. The
              flags are the internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h)  and the 'HW address' is the physi-
              cal layer mapping for that IP address if it is known.

              dev    The dev pseudo-file contains network device status infor-
                     mation.  This gives the number of received and sent pack-
                     ets, the number of errors and collisions and other  basic
                     statistics.  These are used by the ifconfig(8) program to
                     report device status.  The format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0
                     is the kernel  hash  slot  for  the  socket,  the  'local
                     address'   is  the  local  address  and  protocol  number
                     pair."St" is the  internal  status  of  the  socket.  The
                     "tx_queue"  and  "rx_queue" are the outgoing and incoming
                     data queue in terms of kernel  memory  usage.  The  "tr",
                     "tm->when", and "rexmits" fields are not used by RAW. The
                     uid field holds the creator euid of the socket.

              snmp   This file holds the ASCII data needed for the  IP,  ICMP,
                     TCP,  and  UDP  management  information bases for an snmp

              tcp    Holds a dump of the TCP socket table. Much of the  infor-
                     mation is not of use apart from debugging. The "sl" value
                     is the kernel  hash  slot  for  the  socket,  the  "local
                     address"  is  the local address and port number pair. The
                     "remote address" is the remote address  and  port  number
                     pair  (if  connected). 'St' is the internal status of the
                     socket. The 'tx_queue' and 'rx_queue'  are  the  outgoing
                     and  incoming data queue in terms of kernel memory usage.
                     The "tr", "tm->when", and "rexmits" fields hold  internal
                     information  of the kernel socket state and are only use-
                     ful for debugging. The uid field holds the  creator  euid
                     of the socket.

              udp    Holds  a dump of the UDP socket table. Much of the infor-
                     mation is not of use apart from debugging. The "sl" value
                     is  the  kernel  hash  slot  for  the  socket, the "local
                     address" is the local address and port number  pair.  The
                     "remote  address"  is  the remote address and port number
                     pair (if connected). "St" is the internal status  of  the
                     socket.  The  "tx_queue"  and "rx_queue" are the outgoing
                     and incoming data queue in terms of kernel memory  usage.
                     The  "tr",  "tm->when", and "rexmits" fields are not used
                     by UDP. The uid field  holds  the  creator  euid  of  the
                     socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

              unix   Lists  the  UNIX domain sockets present within the system
                     and their status.  The format is:
                     Num RefCount Protocol Flags    Type St Path
                      0: 00000002 00000000 00000000 0001 03
                      1: 00000001 00000000 00010000 0001 01 /dev/printer

              Here 'Num' is the kernel table slot number,  'RefCount'  is  the
              number of users of the socket, 'Protocol' is currently always 0,
              'Flags' represent the internal kernel flags holding  the  status
              of  the socket. Currently, type is always '1' (Unix domain data-
              gram sockets are not yet supported in the kernel). 'St'  is  the
              internal state of the socket and Path is the bound path (if any)
              of the socket.

              of  the SCSI IO subsystem.  These files contain ASCII structures
              and are, therefore, readable with cat.

              You can also write to some of the files to reconfigure the  sub-
              system or switch certain features on or off.

              scsi   This  is  a listing of all SCSI devices known to the ker-
                     nel. The listing  is  similar  to  the  one  seen  during
                     bootup.   scsi  currently  supports  only the add-single-
                     device command which allows  root  to  add  a  hotplugged
                     device to the list of known devices.

                     An   echo   'scsi   add-single-device   1   0   5   0'  >
                     /proc/scsi/scsi will cause host scsi1  to  scan  on  SCSI
                     channel 0 for a device on ID 5 LUN 0. If there is already
                     a device known on this address or the address is invalid,
                     an error will be returned.

                     drivername  can currently be NCR53c7xx, aha152x, aha1542,
                     aha1740, aic7xxx, buslogic, eata_dma, eata_pio,  fdomain,
                     in2000,   pas16,   qlogic,   scsi_debug,  seagate,  t128,
                     u15-24f, ultrastore, or wd7000.  These  directories  show
                     up for all drivers that registered at least one SCSI HBA.
                     Every directory contains one file  per  registered  host.
                     Every  host-file  is  named after the number the host was
                     assigned during initialization.

                     Reading these files will usually  show  driver  and  host
                     configuration, statistics etc.

                     Writing to these files allows different things on differ-
                     ent hosts.  For example, with the latency  and  nolatency
                     commands, root can switch on and off command latency mea-
                     surement code in the eata_dma driver. With the lockup and
                     unlock  commands,  root can control bus lockups simulated
                     by the scsi_debug driver.

       self   This  directory  refers  to  the  process  accessing  the  /proc
              filesystem, and is identical to the /proc directory named by the
              process ID of the same process.

              Information about kernel caches.  The columns are:
              See slabinfo(5) for details.

       stat   kernel/system statistics.   Varies  with  architecture.   Common
              entries include:

              cpu  3357 0 4313 1362393

              swap 1 0
                     The number of swap pages that have been  brought  in  and

              intr 1462898
                     The number of interrupts received from the system boot.

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,minor):(noinfo,       read_io_ops,      blks_read,
                     write_io_ops, blks_written)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot  time, in seconds since the epoch (January 1, 1970).

              processes 86031
                     Number of forks since boot.

       swaps  Swap areas in use.  See also swapon(8).

       sys    This directory (present since 1.3.57) contains a number of files
              and  subdirectories  corresponding  to  kernel variables.  These
              variables can be read and sometimes modified using the proc file
              system, and the sysctl(2) system call. Presently, there are sub-
              directories abi, debug, dev, fs, kernel, net, proc,  sunrpc  and
              vm that each contain more files and subdirectories.

              abi    This  directory may be empty.  On some systems, it is not

              debug  This directory may be empty.

              dev    This directory contains device specific  information  (eg
                     dev/cdrom/info).  On some systems, it may be empty.

              fs     This contains the subdirectory binfmt_misc and files den-
                     try-state, dir-notify-enable, dquot-nr,  file-max,  file-
                     nr,  inode-max,  inode-nr, inode-state, lease-break-time,
                     leases-enable,  overflowgid,  overflowuid  super-max  and
                     super-nr with function fairly clear from the name.

              Documentation  for  the files in /proc/sys/binfmt_misc is in the
              kernel sources in Documentation/binfmt_misc.txt.

              The  file  dentry-state   contains   six   numbers,   nr_dentry,
              nr_unused,   age_limit   (age  in  seconds),  want_pages  (pages
              requested by system) and two dummy values.  nr_dentry  seems  to
              be  0  all the time.  nr_unused seems to be the number of unused
              dentries.  age_limit is the age in seconds  after  which  dcache
              entries  can be reclaimed when memory is short and want_pages is
              nonzero when the kernel has called shrink_dcache_pages() and the
              dcache isn't pruned yet.

              The  file dir-notify-enable can be used to disable or enable the

              The file dquot-nr shows  the  number  of  allocated  disk  quota
              entries and the number of free disk quota entries.

              The  file  file-max is a system-wide limit on the number of open
              files for all processes.  (See also setrlimit(2), which  can  be
              used  by  a process to set the per-process limit, RLIMIT_NOFILE,
              on the number of files it may open.)  If you get lots  of  error
              messages  about running out of file handles, try increasing this

              echo 100000 > /proc/sys/fs/file-max

              The kernel constant NR_OPEN imposes an upper limit on the  value
              that may be placed in file-max.

              If  you  increase file-max, be sure to increase inode-max to 3-4
              times the new value of file-max, or you will run out of  inodes.

              The (read-only) file file-nr gives the number of files presently
              opened.  It contains three numbers: The number of allocated file
              handles,  the number of free file handles and the maximum number
              of file handles.  The kernel allocates file handles dynamically,
              but  it  doesn't  free  them  again.  If the number of allocated
              files is close to the maximum, you  should  consider  increasing
              the  maximum.   When  the  number of free file handles is large,
              you've encountered a peak in your usage of file handles and  you
              probably don't need to increase the maximum.

              The  file  inode-max  contains  the  maximum number of in-memory
              inodes.  On some (2.4) systems, it  may  not  be  present.  This
              value  should  be  3-4  times larger than the value in file-max,
              since stdin, stdout and network sockets also need  an  inode  to
              handle  them.  When you regularly run out of inodes, you need to
              increase this value.

              The file inode-nr contains the  first  two  values  from  inode-

              The   file   inode-state   contains  seven  numbers:  nr_inodes,
              nr_free_inodes, preshrink and four dummy values.   nr_inodes  is
              the  number  of  inodes  the  system has allocated.  This can be
              slightly more than inode-max because Linux  allocates  them  one
              pageful at a time.  nr_free_inodes represents the number of free
              inodes.  preshrink is nonzero when the nr_inodes > inode-max and
              the  system  needs to prune the inode list instead of allocating

              The file lease-break-time specifies the grace  period  that  the
              kernel grants to a process holding a file lease (fcntl(2)) after
              it has sent a signal to that process notifying it  that  another
              process  is  waiting to open the file.  If the lease holder does
              not remove or downgrade the lease within this grace period,  the
              kernel forcibly breaks the lease.

              The  file  leases-enable  can  be used to enable or disable file
              leases (fcntl(2)) on a system-wide basis.  If this file contains
              to disk.

              The file super-max controls the maximum number  of  superblocks,
              and  thus  the  maximum number of mounted filesystems the kernel
              can have. You only need to increase super-max  if  you  need  to
              mount  more  filesystems  than  the  current  value in super-max
              allows you  to.   The  file  super-nr  contains  the  number  of
              filesystems currently mounted.

              kernel This  directory  contains files acct, cad_pid, cap-bound,
                     core_uses_pid,  ctrl-alt-del,  dentry-state,  domainname,
                     hostname,  htab-reclaim (PowerPC only), java-appletviewer
                     (binfmt_java, obsolete),  java-interpreter  (binfmt_java,
                     obsolete), l2cr (PowerPC only), modprobe, msgmax, msgmnb,
                     msgmni,  osrelease,  ostype,  overflowgid,   overflowuid,
                     panic,  powersave-nap  (PowerPC  only),  printk,  random,
                     real-root-dev, reboot-cmd (SPARC only), rtsig-max, rtsig-
                     nr,  sem,  sg-big-buff,  shmall,  shmmax,  shmmni, sysrq,
                     tainted, threads-max,  version  and  zero-paged  (PowerPC
                     only) with function fairly clear from the name.

              The  file  acct  contains three numbers: highwater, lowwater and
              frequency.  If BSD-style process  accounting  is  enabled  these
              values  control its behaviour. If free space on filesystem where
              the log lives goes below lowwater percent  accounting  suspends.
              If  free  space gets above highwater percent accounting resumes.
              Frequency determines how often the kernel checks the  amount  of
              free  space  (value  is in seconds). Default values are 4, 2 and
              30.  That is, suspend accounting if <=  2%  of  space  is  free;
              resume  it if >= 4% of space is free; consider information about
              amount of free space valid for 30 seconds.

              The file cap-bound holds the  value  of  the  kernel  capability
              bounding  set  (expressed as a signed decimal number).  This set
              is ANDed against the capabilities permitted to a process  during

              The  file core_uses_pid can be used control the naming of a core
              dump file on Linux 2.4.  If this file contains the value 0, then
              a  core dump file is simply named core.  If this file contains a
              non-zero value, then the core dump file includes the process  ID
              in a name of the form core.PID.

              The file ctrl-alt-del controls the handling of Ctrl-Alt-Del from
              the keyboard.  When the value in this file is 0, Ctrl-Alt-Del is
              trapped  and  sent  to  the init(1) program to handle a graceful
              restart.  When the value is > 0, Linux's reaction  to  a  Vulcan
              Nerve Pinch (tm) will be an immediate reboot, without even sync-
              ing its dirty buffers.  Note: when a program (like  dosemu)  has
              the  keyboard  in 'raw' mode, the ctrl-alt-del is intercepted by
              the program before it ever reaches the  kernel  tty  layer,  and
              it's up to the program to decide what to do with it.

              The  files domainname and hostname can be used to set the NIS/YP
              domainname and the hostname of your box in exactly the same  way
              as the commands domainname and hostname, i.e.:

              name "darkstar" and DNS (Internet Domain Name Server) domainname
              "", not to be confused with the NIS (Network Information
              Service) or YP (Yellow Pages) domainname. These two domain names
              are  in  general  different.  For  a detailed discussion see the
              hostname(1) man page.

              If the file htab-reclaim (PowerPC only) is  set  to  a  non-zero
              value,  the  PowerPC  htab  (see  kernel file Documentation/pow-
              erpc/ppc_htab.txt) is pruned each time the system hits the  idle

              The  file  l2cr (PowerPC only) contains a flag that controls the
              L2 cache of G3 processor boards. If 0, the  cache  is  disabled.
              Enabled if nonzero.

              The  file  modprobe is described by the kernel source file Docu-

              The file msgmax is a system-wide limit  specifying  the  maximum
              number  of  bytes in a single message written on a System V mes-
              sage queue.

              The file msgmni defines the system-wide limit on the  number  of
              message  queue identifiers.  (This file is only present in Linux
              2.4 onwards.)

              The file msgmnb is a system-wide paramter used to initialise the
              msg_qbytes  setting for subsequenly created message queues.  The
              msg_qbytes setting specifies the maximum number  of  bytes  that
              may be written to the message queue.

              The files ostype and osrelease give substrings of /proc/version.

              The  files  overflowgid  and  overflowuid  duplicate  the  files
              /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid.

              The  file  panic  gives read/write access to the kernel variable
              panic_timeout.  If this is zero,  the  kernel  will  loop  on  a
              panic; if nonzero it indicates that the kernel should autoreboot
              after this number of seconds.  When you use the software  watch-
              dog device driver, the recommended setting is 60.

              The  file powersave-nap (PowerPC only) contains a flag.  If set,
              Linux-PPC will use the 'nap' mode of powersaving, otherwise  the
              'doze' mode will be used.

              The  four  values  in  the  file  printk  are  console_loglevel,
              default_message_loglevel, minimum_console_level and default_con-
              sole_loglevel.   These  values  influence printk() behavior when
              printing or logging error messages. See syslog(2) for more  info
              on  the  different  loglevels.   Messages with a higher priority
              than console_loglevel will be printed to the console.   Messages
              without  an  explicit  priority  will  be  printed with priority
              default_message_level.  minimum_console_loglevel is the  minimum
              (highest)   value   to   which   console_loglevel  can  be  set.
              default_console_loglevel  is  the   default   value   for   con-
              what to do after rebooting?

              The  file  rtsig-max  can  be used to tune the maximum number of
              POSIX realtime (queued) signals that can be outstanding  in  the

              The  file  rtsig-nr shows the number POSIX realtime signals cur-
              rently queued.

              The file sem (available in Linux 2.4 onwards) contains 4 numbers
              defining  limits for System V IPC semaphores.  These fields are,
              in order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A system-wide limit on the number of semaphores  in  all
                      semaphore sets.

              SEMOPM  The  maximum  number of operations that may be specified
                      in a semop(2) call.

              SEMNI   A system-wide limit on the maximum number  of  semaphore

              The  file  sg-big-buff shows the size of the generic SCSI device
              (sg) buffer.  You can't tune it just yet, but you  could  change
              it on compile time by editing include/scsi/sg.h and changing the
              value of SG_BIG_BUFF.  However, there shouldn't be any reason to
              change this value.

              The file shmall contains the system-wide limit on the total num-
              ber of pages of System V shared memory.

              The file shmmax can be used to query and set the run time  limit
              on  the  maximum  (System V IPC) shared memory segment size that
              can be created.  Shared memory segments up to 1Gb are  now  sup-
              ported in the kernel.  This value defaults to SHMMAX.

              The  file  shmmni (available in Linux 2.4 and onwards) specifies
              the system-wide maximum number of System V  shared  memory  seg-
              ments that can be created.

              The file version contains a string like:

              #5 Wed Feb 25 21:49:24 MET 1998.TP

              The  '#5'  means  that  this is the fifth kernel built from this
              source base and the date behind it indicates the time the kernel
              was built.

              The file zero-paged (PowerPC only) contains a flag. When enabled
              (non-zero), Linux-PPC will pre-zero pages in the idle loop, pos-
              sibly speeding up get_free_pages.

              The    net This directory contains networking stuff.

              proc   This directory may be empty.
              Subdirectory containing  the  pseudo-files  msg,  sem  and  shm.
              These  files  list the System V Interprocess Communication (IPC)
              objects (respectively: message queues,  semaphores,  and  shared
              memory)  that  currently  exist on the system, providing similar
              information to that available via  ipcs(1).   These  files  have
              headers  and  are  formatted  (one IPC object per line) for easy
              understanding.  ipc(5) provides further background on the infor-
              mation shown by these files.

       tty    Subdirectory  containing the psuedo-files and subdirectories for
              tty drivers and line disciplines.

       uptime This file contains two numbers: the uptime of the  system  (sec-
              onds), and the amount of time spent in idle process (seconds).

              This string identifies the kernel version that is currently run-
              ning.    It   includes   the   contents   of   /proc/sys/ostype,
              /proc/sys/osrelease and /proc/sys/version.  For example:
            Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994


       cat(1), find(1), free(1), mount(1), ps(1), tr(1), uptime(1), chroot(2),
       mmap(2),  readlink(2),   syslog(2),   slabinfo(5),   hier(7),   arp(8),
       dmesg(8),   hdparm(8),  ifconfig(8),  lsmod(8),  lspci(8),  netstat(8),
       procinfo(8), route(8) /usr/src/linux/Documentation/filesystems/proc.txt


       This  roughly conforms to a Linux 2.4.17 kernel.  Please update this as

       Last updated for Linux 2.4.17.


       Note that many strings (i.e., the environment and command line) are  in
       the  internal  format,  with sub-fields terminated by NUL bytes, so you
       may find that things are more readable if you use od -c  or  tr  "\000"
       "\n" to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.


       The material on /proc/sys/fs and /proc/sys/kernel is closely  based  on
       kernel source documentation files written by Rik van Riel.

                                  2002-07-13                           proc(5)