FreeBSD/LiveCD

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This document will describe how to get a rudimentary Live CD built on your own system from a working/running FreeBSD install.

Contents

Getting Started

To begin, start by building world and the proper kernel for your live CD. You can build a live CD on a 64-bit box for 32-bit fairly easily. The process is described briefly here.

Building world and kernel for a live CD is no different than building it for a running system. During the install process, we want to specify a new location, which will be our live CD. You do this with the DESTDIR variable, given to make.

# cd /usr/src
# make buildworld DESTDIR=/path/to/livecd
# make installworld DESTDIR=/path/to/livecd
# make buildkernel DESTDIR=/path/to/livecd
# make installkernel DESTDIR=/path/to/livecd
# make distribution DESTDIR=/path/to/livecd

If you're building a 64-bit live CD on a 32-bit box, or something else, add TARGET_ARCH and TARGET variables to your build/install. Here's an example of a 32-bit build being done on a 64-bit system:

# make buildworld TARGET_ARCH=i386 TARGET=i386 DESTDIR=/path/to/livecd
# make installworld TARGET_ARCH=i386 TARGET=i386 DESTDIR=/path/to/livecd
# make buildkernel TARGET_ARCH=i386 TARGET=i386 DESTDIR=/path/to/livecd
# make installkernel TARGET_ARCH=i386 TARGET=i386 DESTDIR=/path/to/livecd
# make distribution TARGET_ARCH=i368 TARGET=i386 DESTDIR=/path/to/livecd

Configuration / Installing Packages

Once these operations are complete, you will have a 'working' system in /path/to/livecd (make sure the directory exists before putting files there!) Now, you can chroot to this directory and install a ports tree, add packages, etc. Again, if you're building a 32-bit live CD on a 64-bit system, or something similar, you need to do a couple things first.

Setup a working devfs in your chroot:

# mount -t devfs devfs /path/to/livecd/dev
# chroot /path/to/livecd

As above, if you're cross-compiling, you need to set a couple environment variables. Once inside your chroot, set the following environment variables:

MACHINE i386
UNAME_p i386
UNAME_m i386

You should now be able to pkg_add or build any ports you need for your live CD. In our example, we're using this live CD to restore backups via rsync from a remote server.

The following tasks were completed for our example:

  1. Install rsync (pkg_add -rv rsync)
  2. run /etc/rc.d/sshd onestart to create ssh host keys (so they're static on our live cd)
  3. set a password for the root user
  4. enabled root ssh in sshd_config
  5. added a script to /usr/local/etc/rc.d/ to search for and run dhclient on all interfaces
  6. create a memory disk and union mount it over /etc so resolv.conf can be written by dhclient.
  7. create a file /etc/issue if you want a banner displayed prior to login.

Nitty-Gritty

/etc/fstab

/dev/acd0	/		cd9660	ro		0	0
md		/mnt/etc		mfs	rw,-s32m,-S	2	0
md		/mnt/root	mfs	rw,-s32m,-S	2	0
/mnt/etc		/etc		unionfs	rw		0	0
/mnt/root	/root		unionfs	rw		0	0

/usr/local/etc/rc.d/network.sh

#!/bin/sh

echo "Configuring network interfaces for DHCP..."
echo ""
#ifconfig | grep flags | cut -f 1 -d : | grep -vE 'carp|lo|bridge|tun|tap' | xargs -D 1 -I III dhclient III
rawint=`ifconfig | grep flags | cut -f 1 -d : | grep -vE 'carp|lo|bridge|tun|tap'`

for int in $rawint
do
	if [ ! `ifconfig $int | grep "no carrier"` ]; then
		dhclient $int
	fi
done

/etc/rc.conf

## LiveCD Options
update_motd="NO"
syslogd_enable="NO"
sendmail_enable="NONE"
cleanvar_enable="NO"
hostid_enable="NO"
ip6addrctl_enable="NO"
moused_nondefault_enable="NO"
sendmail_submit_enable="NO"
sendmail_outbound_enable="NO"
sendmail_msp_queue_enable="NO"
cron_enable="NO"
crashinfo_enable="NO"
virecover_enable="NO"
newsyslog_enable="NO"
mixer_enable="NO"
root_rw_mount="NO"
hostname="CLX_LIVECD"

## LiveCD Daemons
sshd_enable="YES"

Create ISO

Once the image is built, we create an ISO using mkisofs, which can be had from /usr/ports/sysutils/cdrtools. The following command will create an ISO with the proper options:

# mkisofs -no-emul-boot -R -b boot/cdboot -J -publisher "ClaimLynx, Inc." -V FreeBSD-LiveCD -o ~/clx2.iso path/to/dir/

Test

I test my ISOs using VirtualBox. You're also welcome to burn them to a CD-R/W and try booting from it.

Paring Down

If you need a smaller ISO than the one we have here (about 440MB), you can remove the following things from your /path/to/livecd:

  • /usr/ports
  • /var/db/portsnap

Resources

Links

Man Pages

  • mdmfs

Thanks

  • Josh Paetzel (most of this article)
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