97 lines
4.6 KiB
HTML
97 lines
4.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>The Linux+FreeBSD mini-HOWTO: Sharing swap space between Linux and FreeBSD</TITLE>
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<LINK HREF="Linux+FreeBSD-4.html" REL=next>
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<LINK HREF="Linux+FreeBSD-2.html" REL=previous>
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<LINK HREF="Linux+FreeBSD.html#toc3" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="Linux+FreeBSD-4.html">Next</A>
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<A HREF="Linux+FreeBSD-2.html">Previous</A>
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<A HREF="Linux+FreeBSD.html#toc3">Contents</A>
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<HR>
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<H2><A NAME="s3">3. Sharing swap space between Linux and FreeBSD</A><!--FreeBSD dualboot!swap space, sharing--></H2>
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<P>This section describes how I got Linux and FreeBSD to share a swap partition.
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There may be other ways to get the same result. You can install FreeBSD before
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Linux if you want to, just pay attention to the order of the partitions in the
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FreeBSD slice.
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<P>
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<H2><A NAME="installlinux"></A> <A NAME="ss3.1">3.1 Installing and preparing Linux</A>
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<!--FreeBSD dualboot!Linux, installing--></H2>
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<P>The first step is to install Linux as normal. You have to leave space for the
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FreeBSD slice at your hard drive. You don't have to make a Linux swap
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partition, but if you want one, put it in the space you want to allocate for
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FreeBSD. That way you can delete the Linux swap partition later and use the
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space for FreeBSD.
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<P>When you have installed Linux you have to build a new kernel. Read <B>The
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Linux Kernel HOWTO</B> if this is new to you. You <EM>have</EM> to include both
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<B>UFS filesystem support (read only)</B> and <B>BSD disklabel (FreeBSD
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partition tables) support</B>:
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<PRE>
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UFS filesystem support (read only) (CONFIG_UFS_FS) [N/y/m/?] y
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BSD disklabel (FreeBSD partition tables) support (CONFIG_BSD_DISKLABEL) [N/y/?]
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(NEW) y
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</PRE>
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<P>Install the new kernel and reboot. Remove any line including the word <EM>swap</EM>
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from your <CODE>/etc/fstab</CODE> file if you have made a Linux swap partition.
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<EM>Make sure you have a working Linux boot floppy with the new kernel.</EM> Now
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you are ready to install FreeBSD.
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<P>
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<H2><A NAME="ss3.2">3.2 Installing FreeBSD</A>
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<!--FreeBSD dualboot!FreeBSD, installing--></H2>
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<P>Install FreeBSD as described in the FreeBSD documentation. Remove the Linux
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swap partition if you have made one (you can use the FreeBSD <CODE>fdisk</CODE>
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program.) Pay attention to the order of the partitions in the FreeBSD
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slice. If you use the default labelling the second partition will be the swap
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partition. Complete the installation of FreeBSD and reboot into Linux
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<EM>using the new Linux boot floppy</EM>.
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<P>
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<H2><A NAME="ss3.3">3.3 Setting up the FreeBSD swap partition in Linux</A>
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<!--FreeBSD dualboot!FreeBSD swap partition configuration--></H2>
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<P>Run <CODE>dmesg</CODE> when you have booted into Linux. In the output you should see
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something like this:
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<PRE>
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Partition check:
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hda: hda1 hda2 hda3 hda4 < hda5 hda6 hda7 hda8 >
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</PRE>
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<P>This means that <CODE>/dev/hda4</CODE> is your FreeBSD slice, while
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<CODE>/dev/hda5</CODE>, <CODE>/dev/hda6</CODE>, <CODE>/dev/hda7</CODE> and
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<CODE>/dev/hda8</CODE> are the FreeBSD partitions. If your swap partition is
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the second partition in the slice, it will be <CODE>/dev/hda6</CODE>.
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<P>You have to put the following line into your Linux <CODE>/etc/fstab</CODE> file to
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enable the swap partition:
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<PRE>
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/dev/hda6 none swap sw 0 0
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</PRE>
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<P>While FreeBSD can use any type of partition as swap space, Linux needs a
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special signature in the swap partition. This signature is made by <CODE>mkswap</CODE>.
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FreeBSD ruins this signature when it uses the shared swap partition, so you
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will have to run <CODE>mkswap</CODE> each time you boot into Linux. To do this
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automagically you have to find the script that runs <CODE>swapon</CODE> at boot time.
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In Red Hat Linux it is <CODE>/etc/rc.d/rc.sysinit</CODE>. Put the following line
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into that file just <EM>before</EM> <CODE>swapon -a</CODE>:
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<PRE>
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awk -- '/swap/ && ($1 !~ /#/) { system("mkswap "$1"") }' /etc/fstab
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</PRE>
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<P>This will run <CODE>mkswap</CODE> on any swap partitions in <CODE>/etc/fstab</CODE> every
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time you boot except if they are commented out (having ``#'' as the first
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character in the line.)
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<P>Run <CODE>free</CODE> to check out the size of the swap space when you have rebooted
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into Linux. You should also reboot into FreeBSD to make sure everything works
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as expected. If it does not, you have probably used the wrong partition
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as swap partition. The only solution to that problem is to reinstall FreeBSD
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and try again. Experience is a great teacher. :-)
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<P>
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<HR>
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<A HREF="Linux+FreeBSD-4.html">Next</A>
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<A HREF="Linux+FreeBSD-2.html">Previous</A>
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<A HREF="Linux+FreeBSD.html#toc3">Contents</A>
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