process file system
The process file system, or
implements a view of the system process table inside the file system. It is
normally mounted on /proc
provides a two-level view of
process space, unlike the previous FreeBSD 1.1
implementation. At the highest
level, processes themselves are named, according to their process ids in
decimal, with no leading zeros. There is also a special node called
which always refers to the process
making the lookup request.
Each node is a directory which contains the following entries:
- The debug registers as defined by
dbregs is currently only implemented on
the i386 architecture.
- The type of the executable referenced by the
- A symbolic link to the file from which the process text was read. This can
be used to gain access to the process' symbol table, or to start another
copy of the process. If the file cannot be found, the link target is
- The floating point registers as defined by
struct fpregs in
fpregs is only implemented on machines
which have distinct general purpose and floating point register sets.
- A map of the process' virtual memory.
- 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
- Used for sending signals to the process. Not implemented.
- Used for sending signal to the process group. Not implemented.
- Allows read and write of the kernel osrel value assigned to the process.
It affects the compatibility shims that are turned on and off depending on
the value. Initial process value is read from the ABI note tag in the
executed ELF image, and is zero if the tag not supported by binary format
or was not found.
- Allows read and write access to the process' register set. This file
contains a binary data structure
regs defined in
regs can only be written when the
process is stopped.
- This is a read-only file containing the process current and maximum
limits. Each line is of the format rlimit
current max, with -1 indicating infinity.
- 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
- device name of the controlling terminal, or a minus sign
(“-”) if there is no controlling terminal.
- a list of process flags:
there is a controlling terminal,
sldr if the process is a session
noflags if neither of the
other two flags are set.
- the process start time in seconds and microseconds, comma
- the user time in seconds and microseconds, comma separated.
- the system time in seconds and microseconds, comma separated.
- the wait channel message
- the process credentials consisting of the effective user id and the
list of groups (whose first member is the effective group id) all
- the hostname of the jail in which the process runs, or
-’ to indicate that the process
is not running within a jail.
Each node is owned by the process's user, and belongs to that user's primary
- normal mount point for the
- directory containing process information for process
- directory containing process information for the current process
- the process executable name
- executable type
- executable image
- the process floating point register set
- virtual memory map of the process
- the complete virtual address space of the process
- used for signaling the process
- used for signaling the process group
- the process osrel value
- the process register set
- the process current and maximum rlimit
- the process' current status
To mount a
file system on
mount -t procfs proc
This manual page written by Garrett Wollman
based on the description provided by Jan-Simon
, and revamped later by Mike