Installation guide

38 Chapter 2. The proc File System
These directories are called process directories, as they are named after a program’s process ID and
contain information specific to that process. The owner and group of each process directory is set to
the user running the process. When the process is terminated, its /proc/ process directory vanishes.
Each process directory contains the following files:
• cmdline — This file contains the command issued when starting the process.
• cpu — Provides specific information about the utilization of each of the system’s CPUs. A process
running on a dual CPU system produces output similar to this:
cpu 11 3
cpu0 0 0
cpu1 11 3
• cwd — A symlink to the current working directory for the process.
• environ — Gives a list of the environment variables for the process. The environment variable is
given in all upper-case characters, and the value is in lower-case characters.
• exe — A symlink to the executable of this process.
• fd — A directory containing all of the file descriptors for a particular process. These are given in
numbered links:
total 0
lrwx------ 1 root root 64 May 8 11:31 0 -> /dev/null
lrwx------ 1 root root 64 May 8 11:31 1 -> /dev/null
lrwx------ 1 root root 64 May 8 11:31 2 -> /dev/null
lrwx------ 1 root root 64 May 8 11:31 3 -> /dev/ptmx
lrwx------ 1 root root 64 May 8 11:31 4 -> socket:[7774817]
lrwx------ 1 root root 64 May 8 11:31 5 -> /dev/ptmx
lrwx------ 1 root root 64 May 8 11:31 6 -> socket:[7774829]
lrwx------ 1 root root 64 May 8 11:31 7 -> /dev/ptmx
• maps — Contains memory maps to the various executables and library files associated with this
process. This file can be rather long, depending upon the complexity of the process, but sample
output from the sshd process begins like this:
08048000-08086000 r-xp 00000000 03:03 391479 /usr/sbin/sshd
08086000-08088000 rw-p 0003e000 03:03 391479 /usr/sbin/sshd
08088000-08095000 rwxp 00000000 00:00 0
40000000-40013000 r-xp 00000000 03:03 293205 /lib/ld-2.2.5.so
40013000-40014000 rw-p 00013000 03:03 293205 /lib/ld-2.2.5.so
40031000-40038000 r-xp 00000000 03:03 293282 /lib/libpam.so.0.75
40038000-40039000 rw-p 00006000 03:03 293282 /lib/libpam.so.0.75
40039000-4003a000 rw-p 00000000 00:00 0
4003a000-4003c000 r-xp 00000000 03:03 293218 /lib/libdl-2.2.5.so
4003c000-4003d000 rw-p 00001000 03:03 293218 /lib/libdl-2.2.5.so
• mem — The memory held by the process. This file cannot be read by the user.
• root — A link to the root directory of the process.
• stat — The status of the process.
• statm — The status of the memory in use by the process. Below is a sample /proc/statm file:
263 210 210 5 0 205 0
The seven columns relate to different memory statistics for the process. From left to right, they
report the following aspects of the memory used:
1. Total program size, in kilobytes
2. Size of memory portions, in kilobytes
3. Number of pages that are shared