June 29, 2005

Linux to the rescue: A review of three system rescue CDs

Author: Aditya Nag

We've all had this nightmare. You turn on your functioning Windows/Linux
PC, and all you get is a blank screen, or a message telling you that certain
files are missing, or the kernel has panicked for some obscure reason. Nothing
works, and you need the data on your machine. Yes, now's the time to whip
out that trusty backup disk, and heave a sigh of relief that all the important
stuff is backed up, right? Well, think again.

Most people do not back up on a daily, or even a weekly basis. Some people
do not back up at all. Yes, there are uber-geeks with scripts that back up
all their work on an hourly basis to offshore servers, but in a small business
scenario, there are times when you have to get data off a computer
that has crashed.

Here's where you can use the Source, Luke! The world of open source has
many wonderful tools for just such a life-or-death situation. Think of them as paramedics for your computer. While they may not be able to restore your machine to full
functionality, they are a quick way of running tests and diagnostics on the
disabled machine. In a pinch, you can use them to save important files on
a different machine on the network, or burn a CD, before sending the machine
off to be fixed.

This article
reviews three open source rescue CDs: System
Rescue CD
, LNX-BBC, and CDlinux. These are all small downloads,
ranging from 17 to 110MB, specifically designed to perform
system rescue. To test the three, I used a recent AMD Athlon 2400+ machine with 256MB RAM, onboard LAN, and a Nvidia graphics
card. The test machine had Windows XP Professional loaded on an NTFS partition on a SATA drive
and Centos 4 on an ext3 partition on a PATA drive.

I tested the three for basic rescue features: mounting partitions
to read and write data, disk management (format, partition, etc.), network
access, CD/DVD writing, and virus scanning. These are the most important rescue disk features, and if they work well, you are well on your way to getting your machine working again.

System Rescue CD

System Rescue CD is the largest download at 110MB. It includes:

  • Linux-kernel-2.4.27-xfs
  • GNU-Parted-1.6.11 -- This reliable text-based partition editor is the best Linux partition tool.
  • QtParted and PartGui are regarded as the
    best free PartitionMagic clones for Linux, and you can use these two graphical partition tools without XFree86. They work with QtEmbedded and allow you to see a chart
    of your hard disk, create, format, delete, and modify partitions.
  • Partimage-0.6.4 is a Ghost/DriveImage clone for Linux.
  • GRUB-0.94 / LILO-22.5 -- These tools are the most common bootloaders used with Linux. You can restore your bootloader from this System Rescue CD. For example, if Windows removed GRUB, you can run GRUB from this CD and reinstall the bootloader.
  • File system tools
  • Evms 2.3 is a powerful logical volume manager.
  • Archiving tools tar/gzip/bzip2 are provided for Unix users. Zip/unzip, while
    rar/unrar/unace are provided for Windows users.

In addition to these components, System Rescue CD includes editors, partition table tools, CD/DVD burning tools, network admin tools, security tools, an anti-virus package, and many other tools that are useful in rescuing your system.

System Rescue CD provides good documentation on its Web site, including a
46-page PDF/HTML manual that gives step-by-step guidance to help you through common tasks. If you have little or no experience with Linux, it's a welcome addition.

After burning the ISO image
to a CD, I rebooted my test machine with the CD in the drive. The machine
presented me with a boot screen, where I could choose to boot with the default
settings, look up help, or access a menu. I chose the menu, which led me to an ncurses-based screen where I could change the graphics mode, disable the framebuffer, and choose between various keyboard layouts and other kernel parameters, such as enabling or disabling DMA and APIC. Even though
you can manually give all these parameters to the kernel before starting it,
many users will appreciate not having to look up the commands. The interface is easy to navigate and lays out the options in an intuitive manner.

After choosing a sensible set of options for my machine, I booted the System Rescue CD. The standard Linux console messages scrolled by, and after hardware detection, the system dropped me into a console.

I first checked Internet and network connectivity. The system took an address
from my router, and I was able to ping other machines on my network, as well
as connect to the Internet using Lynx.

I could easily mount partitions, but the NTFS partition was mounted read-only by default. System Rescue CD includes Captive, a program that mounts NTFS partitions with full read/write access, which is useful for situations where NTOSkernel.exe or other important
Windows system files get corrupted. To mount NTFS partitions using this, you need to have Windows installed on your machine. You have to mount the partition using the standard Linux drivers, then run the Captive program, which copies some files from your Windows installation and tells you how to mount the partition. I found it fairly easy to use, and it worked like a charm. I created, copied, and deleted files and directories without a single
problem.

The next step was to recover data from the computer by copying files to a different machine over the network. I used the SMBFS support to mount a shared directory and copy files into it. It worked without any problems. Burning a CD was easy through the command line.

I tried initializing a new drive and resizing a NTFS partition with QtParted. Both
operations worked without any problems. The NTFS resizing functionality is especially
useful if you need to install a Linux distro but don't have sufficient free space. Some distros come with a built-in resizing functionality, but it's nice to have this feature handy.

In case you need to clone a hard drive or partition, System Rescue CD includes Partimage. Its interface is easy to learn. The trio of QtParted, GNU Parted, and Partimage take care of all the disk management-related tasks.

An anti-virus scanner is another welcome inclusion. ClamAV scans your drive for
viruses, and if you have mounted your NTFS partitions with Captive, it will
remove them. The manual details the steps needed to update the virus definitions
and start a scan. You need a functioning Internet connection to get the
latest definitions. Once the definitions are downloaded, ClamAV scans the
specified partition for viruses. This is useful when you are stuck with a
virus that Windows-based virus scanners are unable to remove. I
wish some sort of spy/adware removal software were available for Linux, so
that scanning and removing spy/adware could be this easy.

System Rescue CD works well for a huge number of rescue-related tasks. Experienced
sysadmins can even create their own versions of it. The documentation is simple and
clear, and contains step-by-step instructions for the most common tasks.

CDlinux

The next rescue CD that I tried was CDlinux. This is a much smaller download at only 17MB, and the feature set is correspondingly smaller as well.

CDlinux boots up with a help screen telling you about the various kernel options. You can
choose your graphics mode and configure a CD writer.

The normal Linux bootup process proceeds, following which you can log in
as root. The first thing I tried was mounting my SATA drive, only to discover that CDlinux doesn't support SATA. It may be possible to enable support by loading kernel modules, but you'll need to know the exact kernel module,
or download the source and compile it -- a time-consuming process that may not work. In an emergency situation, you don't have the time to sit and figure out stuff like this.
Without SATA support I was un able to test any of the NTFS mounting and copying features. The
Centos installation mounted right up, however, and I was able to copy files to and from it.

Internet and network access worked right away. Mounting an SMB partition worked, and copying files across the network was easy. CDlinux includes GNU Parted, so disk management is covered. Gpart lets you restore a damaged partition table. The only thing missing is some documentation. Unless you really know your way around Linux, you'll need to get some help from the Internet, or
an experienced user. The Web site is rather sparse, but it does offer a little help to get you started. Don't expect too much from the Mini-HOWTO; be prepared to do some reading on the Net, and you'll be fine.

CDlinux is aimed at a different audience than that of the System Rescue CD. While
the latter tries to be the perfect recovery tool, and largely succeeds, CDlinux
provides the bare minimum to get you up and running.

CDlinux is a good a choice when you need to quickly get some data off a non-functioning
PC. Its 17MB download size works for dial-up users and is trivial for broadband users.
You can quickly boot up, copy data to another machine on the network, a secondary hard drive, or a CD. The lack of SATA support is a letdown, but future versions will probably include it. It is possible to create
a customized CDlinux distribution, which includes only what you need.

CDlinux can help you perform more complex tasks, but you'll need to be an experienced Linux user. A Windows user would be well advised to stick to the System Rescue CD.

LNX-BBC

LNX-BBC is a Linux distribution optimized to fit onto a CD that is the size of a business card. At 48MB, it falls neatly in between CDlinux and the System Rescue CD. A Bootable Business Card (BBC) is easy to carry in your wallet and has a capacity of about 50MB. Of course, there's nothing stopping you from putting CDlinux or a similar small distro onto a business card CD.

The bootup is similar to that of CDlinux. A help screen shows you some kernel options and various function keys leads you to information about the project. Choosing a proper framebuffer mode is important because LNX-BBC includes a functional X11 server and a few graphical tools, notably Ethereal and BrowseX.

LNX-BBC was the only distro I tested that did not automatically configure the network without my typing in a command. After I did this, I was able to ping other computers on my network and browse the Internet. SATA support
was non-existent, though mounting the CentOS partition worked. Mounting a Windows shared folder using SMBFS failed with an error message.

LNX-BBC includes a graphical browser, which can come in handy. Unfortunately,
BrowseX is an old browser, dating back to 2003. In fact, LNX-BBC is also rather dated, with the last version being released in May 2003. Development seems to have slowed down or stopped altogether.

I liked LNX-BBC's inclusion of Ethereal. It's handy for quick network troubleshooting and packet sniffing. I administer a large network (+400 machines), and I can think of many uses for this.

LNX-BBC includes some nice tools and can be used to perform system repair and recovery; however, the dated nature of the CD means that better alternatives exist. It's difficult to recommend LNX-BBC, but still, it does most of what it's supposed to, so it is functional. And, of course, you can carry it in your wallet.

Recommendations

Of the three CDs, the System Rescue CD is the best in terms of features and hardware support. Functionality and compatibility come at the price of size, though, and dial-up users may find the large file difficult
to download. At 17MB, CDlinux has the size advantage, and it can quickly copy data to a diskette or across a network.

I decided to keep a copy of the System Rescue CD for its well-rounded, fully featured benefits, and CDlinux for its speed. Although LNX-BBC is functional and has some nice features, the other two CDs are more useful.

The number of open source rescue CDs are increasing everyday. A great
resource for finding a live CD is Live CD List. Frequently
updated, this site lists live CDs of all sorts, not just rescue CDs, so it's
a good place to find a live CD tailored to your needs.

Click Here!