Four rescue systems compared

Emergency Response

Everything You Need

The reputation of being just a desktop system still clings unfairly to Knoppix. Although it starts the LXDE graphical user interface in standard mode out of the box, a text mode without X11 is also available. This is especially important because it is not much fun operating a graphical interface through the VNC client of IPMI, DRAC, iLO, or RSA.

Once you have logged into Knoppix, several options present themselves. You will usually want to access the rescue system via SSH to get rid of the VNC console. This is no problem with Knoppix – an SSH server is included. The network configuration can also be changed on the fly, as long as you are logged in locally via VNC console.

Knoppix impresses with its cornucopia of tools for system administration. LVM confidently handles the distribution so that administrators have access to all logical volumes (LVs). The same applies to software RAID configurations with the MD/RAID driver. As soon as the logical drive – be it an LVM LV or MD/RAID device – is working, chroot is also available. You can then tinker with the broken system as if it had booted.

Having 32- and 64-bit binaries bundled on the Knoppix DVD image is also practical. You can be sure that you will be able to process any system with the same DVD and not need separate recovery media. However, the versatility has a snag: Version 7.4.2 of Knoppix is 4GB and, as you will see, clearly exceeds the size of its competitors.

Knoppix is made of a mixture of Debian "stable" topped off with packages from the testing branch. The kernel for Knoppix 7.4.2 is the no longer totally new 3.16; Knoppix version 7.5 takes it up to the more recent 3.18.6.

Modified Versions

Knopper provides a detailed guide on the Knoppix website for creating a locally modified version of the DVD [2]. This process might take awhile, but it also ultimately gives you perfect results that are adapted to your circumstances.

Anyone who needs a special kernel module in Knoppix should follow his instructions: The corresponding module that must then be installed in a second unzipped Knoppix hierarchy can be built from an unzipped Knoppix. This second version of Knoppix serves as a golden master for the new DVD, which is available for use at the end of the process.

Grml: All-Purpose Weapon

Just mentioning Grml [3] (Figure 2) can cause administrators to nod sympathetically. Little wonder, because its inventor Michael Prokop designed Grml as an all-purpose tool for administrators and has stayed faithful to this line for years. Grml was created in response to specific needs: To give administrators exactly the tools they need for everyday use for everything from debugging systems to reviving failed servers and performing other maintenance work that is impossible from within the production system.

Figure 2: The classic: Grml is the most comprehensive tool for administrators wanting to resuscitate an ailing server.

Grml is virtually the counter-concept of Knoppix: Whereas everything was colorful and graphical with Knoppix in the beginning, and the emergency options were only added gradually, Grml was designed for professionals from the beginning.

To this day, Grml only contains a rudimentary graphical interface. If you insist on X11, you might be able to use Fluxbox as a window manager, but ultimately X11 is more of an annoyance when you are trying to save servers. Grml might have reduced graphics because large flash memories were rare in its early days.

Today, Grml can be found in three forms: Grml32 and Grml64, each about 350MB and intended for 32- and 64-bit systems, respectively, and Grml96, which combines both images, yet still fits on a CD. You will never have to download more than 700MB to fill up your toolbox.

Grml does not show any weaknesses in terms of functionality. Almost any conceivable sys admin task can be performed using the system: including LVM and software RAID drives, as well as devices encrypted with Dmcrypt. An SSH server is onboard to avoid the need for remote VNC. The Z shell, which is the default in Grml, might be an unusual choice for many administrators, but it really doesn't cause a problem in everyday life. Anyone who is accustomed to Bash can cope with Zsh.

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