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RedHat 9 (Linux i386) - man page for proc (redhat section 5)

PROC(5) 			    Linux Programmer's Manual				  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 changed.

       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 following 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 prop-
		     erly. In bash, you may use pwd -P.

		     This  file  contains the environment for the process.  The entries are sepa-
		     rated 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 lilo(8).)

	      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 process as [number].

		     Under Linux 2.0 and earlier exe is a pointer to the binary  which	was  exe-
		     cuted, and appears as a symbolic link. A readlink(2) call on the exe special
		     file under Linux 2.0 returns a string in the format:


		     For example, [0301]:1502 would be inode 1502 on device major 03  (IDE,  MFM,
		     etc. drives) minor 01 (first partition on the first drive).

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

	      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 out-
		     put, can be effectively foiled this way, assuming that -i is the flag desig-
		     nating an input file and -o is the flag designating an output file:
		     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 fact.

	      maps   A file containing the currently mapped memory regions and their access  per-

		     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/ld-2.2.4.so
	40013000-40015000 rw-p 00012000 03:0c 4165	 /lib/ld-2.2.4.so
	4001f000-40135000 r-xp 00000000 03:0c 45494	 /lib/libc-2.2.4.so
	40135000-4013e000 rw-p 00115000 03:0c 45494	 /lib/libc-2.2.4.so
	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.

	      mem    Via the mem file one can access the pages	of  a  process's  memory  through
		     open(2), read(2), and fseek(3).

	      root   Unix and Linux support the idea of a per-process root of the filesystem, set
		     by the chroot(2) system call.  Root points to  the  file  system  root,  and
		     behaves as exe, fd/*, etc. do.

	      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 currently owns the tty that
			    the process is connected to.

		     flags %lu
			    The  flags of the process.	The math bit is decimal 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

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

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

		     utime %lu
			    The number of jiffies that this process has been  scheduled  in  user

		     stime %lu
			    The  number of jiffies that this process has been scheduled in kernel

		     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

		     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
			    The current EIP (instruction pointer).

		     signal %lu
			    The bitmap of pending signals (usually 0).

		     blocked %lu
			    The bitmap of blocked signals (usually 0, 2 for shells).

		     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  textual  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  eas-
		     ier for humans to parse.

       bus    Contains subdirectories for installed busses.

	      pci    Contains  various bus subdirectories and pseudo-files containing 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 sup-
	      ported architecture a different list.  Two common entries are processor which gives
	      CPU  number  and	bogomips; a system constant that is calculated during kernel ini-
	      tialization.  SMP machines have information for each CPU.

	      Text listing of major numbers and device groups.	 This  can  be	used  by  MAKEDEV
	      scripts for consistency with the kernel.

       dma    This is a list of the registered ISA DMA (direct memory access) channels in use.

       driver Empty subdirectory.

	      List of the execution domains (ABI personalities).

       fb     Frame buffer information when CONFIG_FB is defined during kernel compilation.

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

       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  mes-
	      sages.   A  process  must have superuser privileges 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.

       ksyms  This holds the kernel exported symbol definitions used by the modules(X)	tools  to
	      dynamically link and bind loadable modules.

	      The  load  average  numbers  give  the number of jobs in the run queue (state R) or
	      waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes.   They  are  the
	      same as the load average numbers given by uptime(1) and other programs.

       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 during 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  ker-

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

       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/Documentation/mtrr.txt   for

       net    various net pseudo-files, all of which give the status of some part of the network-
	      ing layer.  These files contain ASCII structures and are, therefore, readable  with
	      cat.   However, the standard 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 dynamically learned and pre-programmed ARP
		     entries.  The format is:

	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 hard-
	      ware  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
	      physical layer mapping for that IP address if it is known.

	      dev    The  dev  pseudo-file contains network device status information. This gives
		     the number of received and sent packets, 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

	      rarp   This file uses the same format as the arp	file  and  contains  the  current
		     reverse mapping database used to provide rarp(8) reverse address lookup ser-
		     vices. If RARP is not configured into the kernel,	this  file  will  not  be

	      raw    Holds  a dump of the RAW socket table. Much of the information 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 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 manage-
		     ment information bases for an snmp agent.

	      tcp    Holds a dump of the TCP socket table. Much of the information 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 useful for debugging. The uid field holds the cre-
		     ator euid of the socket.

	      udp    Holds a dump of the UDP socket table. Much of the information 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
	      datagram	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.

	      Contains major and minor numbers of each partition as well as number of blocks  and
	      partition name.

       pci    This  is	a listing of all PCI devices found during kernel initialization and their

       scsi   A directory with the scsi midlevel pseudo-file and  various  SCSI  lowlevel  driver
	      directories,  which  contain a file for each SCSI host in this system, all of which
	      give the status of some part 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 subsystem or switch cer-
	      tain features on or off.

	      scsi   This is a listing of all SCSI devices known to the kernel.  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 con-
		     tains one file per registered host. Every host-file is named after the  num-
		     ber the host was assigned during initialization.

		     Reading these files will usually show driver and host configuration, statis-
		     tics etc.

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

       self   This directory refers to the process accessing the /proc filesystem, and is identi-
	      cal 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
		     The  number  of jiffies (1/100ths of a second) that the system spent in user
		     mode, user mode with low priority (nice), system mode, and  the  idle  task,
		     respectively.   The  last	value should be 100 times the second entry in the
		     uptime pseudo-file.

	      page 5741 1808
		     The number of pages the system paged in and the number that were  paged  out
		     (from disk).

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

	      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 modi-
	      fied  using  the	proc file system, and the sysctl(2) system call. Presently, there
	      are subdirectories 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 present.

	      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  dentry-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

	      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 dnotify interface
	      described in fcntl(2) on a system-wide basis.  A value of 0 in this  file  disables
	      the interface, and a value of 1 enables it.

	      The  file dquot-max shows the maximum number of cached disk quota entries.  On some
	      (2.4) systems, it is not present.  If the number of free cached disk quotas is very
	      low  and	you have some awesome number of simultaneous system users, you might want
	      to raise the limit.

	      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 pro-
	      cesses.  (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 value:

	      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  con-
	      tains  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 han-
	      dles 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-state.

	      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 more.

	      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 the value 0, leases are disabled.  A non-
	      zero value enables leases.

	      The files overflowgid and overflowuid allow you to change the value  of  the  fixed
	      UID  and GID.  The default is 65534.  Some filesystems only support 16-bit UIDs and
	      GIDs, although in Linux UIDs and GIDs are 32 bits. When one of these filesystems is
	      mounted  with  writes enabled, any UID or GID that would exceed 65535 is translated
	      to the overflow value before being written 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

	      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,  ver-
		     sion 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 sus-
	      pends. If free space gets above highwater percent  accounting  resumes.	Frequency
	      determines  how  often the kernel checks the amount of free space (value is in sec-
	      onds). 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 exec.

	      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 syncing 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  host-
	      name, i.e.:

	      # echo "darkstar" > /proc/sys/kernel/hostname
	      # echo "mydomain" > /proc/sys/kernel/domainname

	      has the same effect as

	      # hostname "darkstar"
	      # domainname "mydomain"

	      Note,  however,  that the classic darkstar.frop.org has the hostname "darkstar" and
	      DNS (Internet Domain Name Server) domainname "frop.org", 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  host-
	      name(1) man page.

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

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

	      The file modprobe is described by the kernel source file Documentation/kmod.txt.

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

	      The  file msgmni defines the system-wide limit on the number of message queue iden-
	      tifiers.	(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 maxi-
	      mum 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
	      watchdog 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_console_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  con-
	      sole_loglevel  will be printed to the console.  Messages without an explicit prior-
	      ity will be printed with priority default_message_level.	 minimum_console_loglevel
	      is  the minimum (highest) value to which console_loglevel can be set.  default_con-
	      sole_loglevel is the default value for console_loglevel.

	      The directory random contains various parameters controlling the operation  of  the
	      file /dev/random.

	      The  file  real-root-dev is documented in the kernel source file Documentation/ini-

	      The file reboot-cmd (Sparc only) seems to be a way to give an argument to the SPARC
	      ROM/Flash boot loader. Maybe to tell it 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 system.

	      The file rtsig-nr shows the number POSIX realtime signals currently 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 identifiers.

	      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 number of pages of Sys-
	      tem 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  seg-
	      ments up to 1Gb are now supported in the kernel.	This value defaults to SHMMAX.

	      The file shmmni (available in Linux 2.4 and onwards) specifies the system-wide max-
	      imum number of System V shared memory segments 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, possibly speeding up get_free_pages.

	      The    net This directory contains networking stuff.

	      proc   This directory may be empty.

	      sunrpc This directory supports Sun remote procedure call for  network  file  system
		     (NFS).  On some systems, it is not present.

	      vm     This directory contains files for memory management tuning, buffer and cache

	      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  simi-
	      lar  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  fur-
	      ther background on the information 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 (seconds), and the  amount
	      of time spent in idle process (seconds).

	      This  string  identifies the kernel version that is currently running.  It includes
	      the contents of /proc/sys/ostype, /proc/sys/osrelease and  /proc/sys/version.   For
	    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), read-
       link(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/Documenta-

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

       Last updated for Linux 2.4.17.

       Note that many strings (i.e., the environment and command line) are in the  internal  for-
       mat,  with  sub-fields terminated by NUL bytes, so you may find that things are more read-
       able 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  docu-
       mentation files written by Rik van Riel.

					    2002-07-13					  PROC(5)

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