<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML ><HEAD ><TITLE >How to access the /proc-filesystem</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="Linux IPv6 HOWTO (en)" HREF="index.html"><LINK REL="UP" TITLE="Kernel settings in /proc-filesystem" HREF="chapter-kernel-settings.html"><LINK REL="PREVIOUS" TITLE="Kernel settings in /proc-filesystem" HREF="chapter-kernel-settings.html"><LINK REL="NEXT" TITLE="Entries in /proc/sys/net/ipv6/" HREF="proc-sys-net-ipv6..html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Linux IPv6 HOWTO (en)</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="chapter-kernel-settings.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 11. Kernel settings in /proc-filesystem</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="proc-sys-net-ipv6..html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN1371" ></A >11.1. How to access the /proc-filesystem</H1 ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1373" ></A >11.1.1. Using “cat” and “echo”</H2 ><P >Using “cat” and “echo” is the simplest way to access the /proc filesystem, but some requirements are needed for that</P ><P ></P ><UL ><LI ><P >The /proc-filesystem had to be enabled in kernel, means on compiling following switch has to be set</P ></LI ></UL ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >CONFIG_PROC_FS=y</PRE ></FONT ></TD ></TR ></TABLE ><P ></P ><UL ><LI ><P >The /proc-filesystem was mounted before, which can be tested using</P ></LI ></UL ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># mount | grep "type proc" none on /proc type proc (rw)</PRE ></FONT ></TD ></TR ></TABLE ><P ></P ><UL ><LI ><P >You need read and sometimes also write access (normally root only) to the /proc-filesystem</P ></LI ></UL ><P >Normally, only entries in /proc/sys/* are writable, the others are readonly and for information retrieving only.</P ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN1388" ></A >11.1.1.1. Retrieving a value</H3 ><P >The value of an entry can be retrieved using “cat”:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># cat /proc/sys/net/ipv6/conf/all/forwarding 0</PRE ></FONT ></TD ></TR ></TABLE ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN1392" ></A >11.1.1.2. Setting a value</H3 ><P >A new value can be set (if entry is writable) using “echo”:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># echo "1" >/proc/sys/net/ipv6/conf/all/forwarding</PRE ></FONT ></TD ></TR ></TABLE ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1396" ></A >11.1.2. Using “sysctl”</H2 ><P >Using the “sysctl” program to access the kernel switches is a modern method today. You can use it also, if the /proc-filesystem isn't mounted. But you have only access to /proc/sys/*!</P ><P >The program “sysctl” is included in package “procps” (on Red Hat Linux systems).</P ><P ></P ><UL ><LI ><P >The sysctl-interface had to be enabled in kernel, means on compiling following switch has to be set</P ></LI ></UL ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >CONFIG_SYSCTL=y</PRE ></FONT ></TD ></TR ></TABLE ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN1404" ></A >11.1.2.1. Retrieving a value</H3 ><P >The value of an entry can be retrieved now:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.all.forwarding = 0</PRE ></FONT ></TD ></TR ></TABLE ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN1408" ></A >11.1.2.2. Setting a value</H3 ><P >A new value can be set (if entry is writable):</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># sysctl -w net.ipv6.conf.all.forwarding=1 net.ipv6.conf.all.forwarding = 1</PRE ></FONT ></TD ></TR ></TABLE ><P >Note: Don't use spaces around the “=” on setting values. Also on multiple values per line, quote them like e.g.</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ># sysctl -w net.ipv4.ip_local_port_range="32768 61000" net.ipv4.ip_local_port_range = 32768 61000</PRE ></FONT ></TD ></TR ></TABLE ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN1414" ></A >11.1.2.3. Additionals</H3 ><P >Note: There are sysctl versions in the wild which displaying “/” instead of the “.”</P ><P >For more details take a look into sysctl's manpage.</P ><P >Hint: for digging fast into the settings, use the option “-a” (display all entries) in conjunction with “grep”.</P ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN1419" ></A >11.1.3. Values found in /proc-filesystems</H2 ><P >There are several formats seen in /proc-filesystem:</P ><P ></P ><UL ><LI ><P >BOOLEAN: simple a “0” (false) or a “1” (true)</P ></LI ><LI ><P >INTEGER: an integer value, can be unsigned, too</P ></LI ><LI ><P >more sophisticated lines with several values: sometimes a header line is displayed also, if not, have a look into the kernel source to retrieve information about the meaning of each value...</P ></LI ></UL ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="chapter-kernel-settings.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="proc-sys-net-ipv6..html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Kernel settings in /proc-filesystem</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="chapter-kernel-settings.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Entries in /proc/sys/net/ipv6/</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
