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MOUNT_PROCFS(8) System Manager's Manual MOUNT_PROCFS(8)

mount_procfsmount the process file system

mount_procfs [-o options] /proc mount_point

The mount_procfs command attaches an instance of the process namespace to the global filesystem namespace. The conventional mount point is /proc. This command is normally executed by mount(8) at boot time.

The options are as follows:

Options are specified with a -o flag followed by a comma separated string of options. See the mount(8) man page for possible options and their meanings. The following procfs specific option is also available:
Add Linux compatibility links and nodes to procfs.

The root of the process filesystem contains an entry for each active process. These processes are visible as a directory whose name is the process's PID. In addition, the special entry curproc references the current process.

Each directory contains several files.

Process command line parameters, separated by NULs.
A reference to the vnode from which the process text was read. This can be used to gain access to the process's symbol table, or to start another copy of the process.
The complete virtual memory image of the process. Only those address which exist in the process can be accessed. Reads and writes to this file modify the process. Writes to the text segment remain private to the process.
The process status. This file is read-only and returns a single line containing multiple space-separated fields as follows:

  • Command name.
  • Process ID.
  • Parent process ID.
  • Process group ID.
  • Session ID.
  • major,minor of the controlling terminal, or -1,-1 if there is no controlling terminal.
  • List of process flags: ctty if there is a controlling terminal, sldr if the process is a session leader, or noflags if neither of the other two flags are set.
  • Process start time in seconds and microseconds, comma separated.
  • User time in seconds and microseconds, comma separated.
  • System time in seconds and microseconds, comma separated.
  • Wait channel message.
  • Process credentials consisting of the effective user ID and the list of groups (whose first member is the effective group ID), all comma separated.

Statistics reported by df(1) on a procfs filesystem will indicate virtual memory used/available instead of ‘disk space’, and the number of process slots used/allocated instead of ‘inodes’. The block size of the filesystem is the system page size.


mount(2), fstab(5), mount(8), umount(8)

The mount_procfs utility first appeared in 4.4BSD.

This filesystem may not be NFS-exported since most of the functionality of procfs requires that state be maintained.

December 28, 2011 OpenBSD-5.3