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<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN">
<HTML
><HEAD
><TITLE
>The /proc filesystem</TITLE
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN595"
>The <TT
CLASS="FILENAME"
>/proc</TT
> filesystem</A
></H1
><P
>The <TT
CLASS="FILENAME"
>/proc</TT
> filesystem contains
a illusionary filesystem. It does not exist on a disk.
Instead, the kernel creates it in memory. It is used to provide
information about the system (originally about processes, hence
the name). Some of the more important files and directories are
explained below. The <TT
CLASS="FILENAME"
>/proc</TT
> filesystem is
described in more detail in the <TT
CLASS="FILENAME"
>proc</TT
> manual page.
<DIV
CLASS="GLOSSLIST"
><DL
><DT
><B
><TT
CLASS="FILENAME"
>/proc/1</TT
></B
></DT
><DD
><P
>A directory with information about
process number 1. Each process has a directory below
<TT
CLASS="FILENAME"
>/proc</TT
> with the name being its process
identification number. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/cpuinfo</TT
></B
></DT
><DD
><P
>Information about the processor,
such as its type, make, model, and perfomance.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/devices</TT
></B
></DT
><DD
><P
>List of device drivers configured into the
currently running kernel. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/dma</TT
></B
></DT
><DD
><P
>Shows which DMA channels are being used
at the moment. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/filesystems</TT
></B
></DT
><DD
><P
>Filesystems configured into the kernel.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/interrupts</TT
></B
></DT
><DD
><P
>Shows which interrupts are
in use, and how many of each there have been.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/ioports</TT
></B
></DT
><DD
><P
>Which I/O ports are in use at the moment.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/kcore</TT
></B
></DT
><DD
><P
>An image of the physical memory of
the system. This is exactly the same size as your
physical memory, but does not really take up that much
memory; it is generated on the fly as programs access it.
(Remember: unless you copy it elsewhere, nothing under
<TT
CLASS="FILENAME"
>/proc</TT
> takes up any disk space
at all.) </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/kmsg</TT
></B
></DT
><DD
><P
>Messages output by the kernel.
These are also routed to <B
CLASS="COMMAND"
>syslog</B
>.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/ksyms</TT
></B
></DT
><DD
><P
>Symbol table for the kernel.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/loadavg</TT
></B
></DT
><DD
><P
>The `load average' of the system; three
meaningless indicators of how much work the system has
to do at the moment. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/meminfo</TT
></B
></DT
><DD
><P
>Information about memory usage, both
physical and swap. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/modules</TT
></B
></DT
><DD
><P
>Which kernel modules are loaded at
the moment. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/net</TT
></B
></DT
><DD
><P
>Status information about network
protocols. </P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/self</TT
></B
></DT
><DD
><P
>A symbolic link to the process
directory of the program that is looking at
<TT
CLASS="FILENAME"
>/proc</TT
>. When two processes look at
<TT
CLASS="FILENAME"
>/proc</TT
>, they get different links.
This is mainly a convenience to make it easier
for programs to get at their process directory.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/stat</TT
></B
></DT
><DD
><P
>Various statistics about the system, such
as the number of page faults since the system was booted.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/uptime</TT
></B
></DT
><DD
><P
>The time the system has been up.
</P
></DD
><DT
><B
><TT
CLASS="FILENAME"
>/proc/version</TT
></B
></DT
><DD
><P
>The kernel version.
</P
></DD
></DL
></DIV
></P
><P
>Note that while the above files tend to be easily
readable text files, they can sometimes be formatted in a way
that is not easily digestable. There are many commands that
do little more than read the above files and format them for
easier understanding. For example, the <B
CLASS="COMMAND"
>free</B
>
program reads <TT
CLASS="FILENAME"
>/proc/meminfo</TT
> and converts
the amounts given in bytes to kilobytes (and adds a little more
information, as well).</P
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