Create A Linux Rescue/Recovery Disc
05-Jul-2008
Found this article by chance and have popped it here for easy reference! It's as simple as it sound - useful in instances where something goes wrong and you can't access your Ubuntu.
Kurt Edelbrock talks you though the process.
Create the live CD environment
First grab the Ubuntu 8.04 live CD ISO file for your system type. You can get this either from the Ubuntu Web site, or use wget on the command line:
wget -v http://releases.ubuntu.com/hardy/ubuntu-8.04-desktop-i386.iso
To work with the image, you'll need to install a few packages to support the squashfs filesystem format, and mkisofs, the utility to create ISO images. On Ubuntu, you can install them with the command
sudo apt-get install squashfs-tools mkisofs.
Now, load the squashfs module, then copy, mount, and extract the contents of the ISO file in order to customize the contents:
sudo modprobe squashfs
mkdir rescue
mv ubuntu-8.04-desktop-i386.iso rescue
cd rescue
mkdir mnt
sudo mount -o loop ubuntu-8.04-desktop-i386.iso mnt
mkdir extract-cd
rsync --exclude=/casper/filesystem.squashfs -a mnt/ extract-cd
mkdir squashfs
sudo mount -t squashfs -o loop mnt/casper/filesystem.squashfs squashfs
mkdir edit
sudo cp -a squashfs/* edit/
You'll want to customize the CD in a chroot environment. Chroot changes the root directory of the environment, allowing you to access the files and applications inside the CD directly, which you must do in order to use tools like apt-get. In order to use a network connection inside chroot, which you'll probably want to do to add new packages, you'll need to copy in the hosts and resolv.conf files to configure your network settings. You can achieve this with the following:
sudo cp /etc/resolv.conf edit/etc/
sudo cp /etc/hosts edit/etc/
Once you've completed these steps, you can start to work inside the live CD. Mount the live CD to the edit/dev mountpoint, then change your root directory into the newly mounted volume. You'll need to mount /proc and /sys volumes to work with the kernel, and export your settings to avoid locale and GPG problems later on:
sudo mount --bind /dev/ edit/dev
sudo chroot edit
mount -t proc none /proc
mount -t sysfs none /sys
export HOME=/root
export LC_ALL=C
Free space by removing unneeded packages
You can configure the packages that are included with the live CD using apt-get or Aptitude. You'll want to free up some space to add the rescue applications; even though the data is compressed, all of it needs to fit on a 700MB CD or on a higher-capacity DVD. You can remove packages and applications that aren't useful for the recovery. I chose to remove the OpenOffice.org suite, the GNOME games set, Ekiga, Ubiquity, Evolution, and the GIMP, saving me around 200MB. If you are comfortable without a command-line environment, you might want to get rid of GNOME and Xorg; if you do that, you need not install GParted and the other graphical tools in the next section. In any case, the goal is to get rid of large applications. To sort all of the installed packages by size, run the following command in the chrooted environment:
dpkg-query -W --showformat='${Installed-Size} ${Package}\n' | sort -nr | less
You can use apt-get to remove a package. Use it with the --purge argument to get rid of configuration files. The sudo command won't work in the chroot, and therefore should be omitted:
apt-get remove --purge package-name
Add rescue applications
Once you have removed all of the unneeded applications from the live CD you can start to add rescue and recovery applications. Generally, rescue CDs include a variety of disk utilities and security tools, as well as networking tools to find support and access outside machines. You may not want all of the applications I mention, and you can add some that I don't. This is your personal boot CD, and should be configured as you see fit. For ideas about what to include on your CD, you might want to check out some of the prebuilt rescue distributions mentioned in the sidebar.
You can install packages from the repositories using apt-get, but you must add the multiverse repository to your /etc/apt/sources.list file:
deb http://us.archive.ubuntu.com/ubuntu/ hardy main multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ hardy main multiverse
A disk partition tool is the staple of a mature boot disk. Fortunately, the Ubuntu live CD comes with GParted, the GNOME Partition Editor, so adding a package isn't required. If you chose to forgo a graphical environment, you should make sure that parted is installed instead to handle partition tables from the command line. If you accidentally delete a partition, installing a program like testdisk can help you recover it, as well as provide a few other basic disk tools. If you are using the ext2 filesystem type and you accidentally delete a file, you'll find the e2undel package helpful in recovering it. If you need to copy an entire partition from a dying disk, or just want to make a backup, partimage is the way to go. You can also use it to restore a partition with a previously made backup.
If you plan to use this disc with Windows machines, you will want to install antivirus and rootkit tools. Clamscan provides quick and easy virus scan with a command-line-based update tool. Chkrootkit is a scanner to find and remove rootkits that could be hiding in your computer. You can use sleuthkit to conduct analysis of your filesystem and browse through hidden files.
After you finish adding packages, clean up your temporary data and unmount the environment:
apt-get clean
rm -rf /tmp/*
rm /etc/resolv.conf
umount /proc
umount /sys
exit
sudo umount edit/dev
Now, regenerate the manifest (which is basically a list of installed packages) and copy in into the correct directory:
chmod +w extract-cd/casper/filesystem.manifest
[following two lines are all one line]
sudo chroot edit dpkg-query -W --showformat='${Package} ${Version}\n' >
extract-cd/casper/filesystem.manifest
sudo cp extract-cd/casper/filesystem.manifest extract-cd/casper/filesystem.manifest-desktop
sudo sed -i '/ubiquity/d' extract-cd/casper/filesystem.manifest-desktop
Compress the filesystem to squeeze it onto a disc:
sudo rm extract-cd/casper/filesystem.squashfs
sudo mksquashfs edit extract-cd/casper/filesystem.squashfs -nolzma
And finally, create the ISO file:
cd extract-cd
[The Following is all one line]
sudo mkisofs -r -V "$IMAGE_NAME" -cache-inodes -J -l -b isolinux/isolinux.bin
-c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o
../ubuntu-8.04-desktop-i386.iso
Once the image file is created, you need to burn it to a disc. You can do that pretty easily with K3b or Brasero. If you want, you can do it from the command line:
cdrecord dev=/dev/cdrom ubuntu-8.04-desktop-i386.iso
Once the CD is finished burning, you should be able to put it into your optical drive and boot into the environment you just created.
This should give you more than enough information to start building your ultimate custom rescue CD. Add the packages and tools you need, and hopefully you'll never be at a loss the next time your computer has a problem during startup.
Posted by Joey Saturday, July 05, 2008
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