<HTML ><HEAD ><TITLE >Adding Support for More Loop Devices </TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.63 "><LINK REL="HOME" TITLE="CDServer-HOWTO" HREF="index.html"><LINK REL="PREVIOUS" TITLE="Procedure" HREF="procedure.html"><LINK REL="NEXT" TITLE="More Information" HREF="moreinfo.html"></HEAD ><BODY CLASS="sect1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >CDServer-HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="procedure.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="moreinfo.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="sect1" ><H1 CLASS="sect1" ><A NAME="addloops" >3. Adding Support for More Loop Devices</A ></H1 ><P > Newer Linux kernels (2.4) allow you to add more loop devices easily by editing <TT CLASS="filename" >/etc/modules.conf</TT > or through the use of a boot parameter. </P ><P > Older kernels (2.2 ?) only had support for 8 loop devices compiled into the kernel. In short, you were only able to share 8 CD's on a network with this default value. In order to support more than that default, you needed to modify the kernel source and recompile a new kernel. </P ><P > Use the following methods to determine which version of the kernel you are running. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >uname -a</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > or </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >cat /proc/version</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="loopmodule" >3.1. Adding the Loop Module Option</A ></H2 ><P > Current kernels allow you to set the number of loop devices supported without recompiling the kernel. One of these methods is to add an options line to <TT CLASS="filename" >/etc/modules.conf</TT >. This method will only work if your loop support has been configured as a loadable kernel module (which is how most major Linux distributions come preconfigured now). </P ><P > Edit <TT CLASS="filename" >/etc/modules.conf</TT > and add the following line. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > options loop max_loop=64 </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > After making the above change, simply reboot. Or you can try to use <B CLASS="command" >rmmod</B > and <B CLASS="command" >insmod</B > to make the change on the fly - but this will not work if you currently have any loop devices mounted (you'll get an error saying loop: Device or resource busy). </P ><P ></P ><DIV CLASS="variablelist" ><DL ><DT >Note</DT ><DD ><P > If you do not have an <TT CLASS="filename" >/etc/modules.conf</TT > file, your module configuration file may be called <TT CLASS="filename" >/etc/conf.modules</TT > (this name is now deprecated). </P ></DD ></DL ></DIV ><P > Continue with <A HREF="addloops.html#loopdev" >Section 3.4</A >. </P ><P > <EM > Thanks to Paul A. Sand for pointing out the /etc/modules.conf option. </EM > </P ></DIV ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="bootprompt" >3.2. Appending to the Boot Prompt</A ></H2 ><P > If your loop support has been compiled directly into the kernel (in other words, it is not loaded as a module), you can append the number of loop devices you would like to support at the linux boot prompt. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >boot:</TT > <B CLASS="command" >linux <TT CLASS="parameter" ><I >max_loop=<TT CLASS="replaceable" ><I >64</I ></TT ></I ></TT ></B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > Or, if you are using <SPAN CLASS="application" ><SPAN CLASS="acronym" >LILO</SPAN ></SPAN >, you can edit your linux boot stanza in <TT CLASS="filename" >/etc/lilo.conf</TT > and add/modify the <TT CLASS="parameter" ><I >append=</I ></TT > line. Here is an example stanza showing <TT CLASS="parameter" ><I >append=</I ></TT > (<EM >note: only add or modify the append line, don't change your whole stanza to look like this one or your system may not boot</EM >). For more information about LILO, consult the <A HREF="http://www.linuxdoc.org/HOWTO/mini/LILO.html" TARGET="_top" >LILO mini-HOWTO</A > at <SPAN CLASS="systemitem" >http://www.linuxdoc.org/HOWTO/mini/LILO.html</SPAN >. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > image=/boot/vmlinuz label=linux root=/dev/hdb5 initrd=/boot/initrd.img append=<TT CLASS="replaceable" ><I >" max_loop=64"</I ></TT > vga=788 read-only </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > After changing <TT CLASS="filename" >/etc/lilo.conf</TT >, you need to run the <B CLASS="command" >lilo</B > command for your changes to take effect. </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >lilo</B > <TT CLASS="computeroutput" > Added linux * Added linux-nonfb Added failsafe Added windows Added floppy </TT > </PRE ></FONT ></TD ></TR ></TABLE ><P > Next restart your system. After your system restarts, you can check your boot command line by typing the following: </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >cat /proc/cmdline</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P ></P ><DIV CLASS="variablelist" ><DL ><DT >Note</DT ><DD ><P > I am not sure if the loop module (compiled as a module) reads <TT CLASS="filename" >/proc/cmdline</TT > when the module is loaded, and therefore may not need an options line <TT CLASS="filename" >/etc/modules.conf</TT >. It's possible that it can (and if it doesn't, it should). To summarize: I have not tested this. </P ></DD ></DL ></DIV ><P > Continue with <A HREF="addloops.html#loopdev" >Section 3.4</A >. </P ><P > <EM > Thanks to Tony Melia for the boot prompt info. </EM > </P ></DIV ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="editkernel" >3.3. Tweaking the Kernel</A ></H2 ><P > If you have an older kernel (v. 2.2) or if you are completely comfortable recompiling the kernel, you can increase the number of loop devices supported by editing the <TT CLASS="filename" >/usr/src/linux/drivers/block/loop.c</TT > file. </P ><P ></P ><DIV CLASS="variablelist" ><DL ><DT >Note</DT ><DD ><P > If you find that the kernel sources are not installed on your machine, you'll need to consult your Linux Distribution's documentation on how to install them (the Kernel Sources come with all distributions - it's part of the <SPAN CLASS="acronym" >GNU</SPAN > <SPAN CLASS="acronym" >GPL</SPAN > licensing). </P ></DD ></DL ></DIV ><P > Change the number in the following line to however many loop devices you'll need. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > #define MAX_LOOP <TT CLASS="replaceable" ><I >16</I ></TT > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > Compile the new kernel or module as the case may be. If you need some help getting started with this, read <TT CLASS="filename" >/usr/src/linux/README</TT > or consult <A HREF="http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html" TARGET="_top" > The Linux Kernel HOWTO</A >. </P ><P > Continue with <A HREF="addloops.html#loopdev" >Section 3.4</A >. </P ></DIV ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="loopdev" >3.4. Creating the Loop Devices in /dev</A ></H2 ><P > You should check how many <TT CLASS="filename" >/dev</TT > entries you have for loop devices. </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >ls -l /dev/loop*</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > The <B CLASS="command" >mknod</B > command creates the devices in the <TT CLASS="filename" >/dev</TT > directory. The loop devices have a major number of <SPAN CLASS="QUOTE" >"7"</SPAN >, and the minor numbers begin at <SPAN CLASS="QUOTE" >"0"</SPAN >. If your <TT CLASS="parameter" ><I >MAX_LOOP</I ></TT > was defined as <SPAN CLASS="QUOTE" >"8"</SPAN > in <TT CLASS="filename" >/usr/src/linux/drivers/block/loop.c</TT >, you should have <TT CLASS="filename" >/dev/loop0</TT > through <TT CLASS="filename" >/dev/loop7</TT >. To create the <TT CLASS="filename" >/dev/loop8</TT > device, use the following command (subsitute the appropriate number you need for both the <SPAN CLASS="QUOTE" >"8's"</SPAN > in the example below). </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >mknod -m660 /dev/loop<TT CLASS="replaceable" ><I >8</I ></TT > b 7 <TT CLASS="replaceable" ><I >8</I ></TT ></B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > Check Owner/Group & Permissions on the new file (using <B CLASS="command" >ls -l</B >). You can change the owner and group with the following command: </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >chown root.disk /dev/loop8</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ><P > You can change the permissions using the following command: </P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > <TT CLASS="prompt" >bash#</TT > <B CLASS="command" >chmod 666 /dev/loop8</B > </PRE ></FONT ></TD ></TR ></TABLE > </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="procedure.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="moreinfo.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Procedure</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >More Information</TD ></TR ></TABLE ></DIV ></BODY ></HTML >