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Knoppix is the Low TCO Desktop Operating System
Copyright (C) 2004 by Steve Litt

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Contents:

Executive Summary

Supporting multiple computers is expensive and time consuming. Here are a few of the challenges:
Knoppix is a breath of fresh air. Its hardware detection is second to none, so installation is quick on all but the most unusual hardware. There is only one installation CD, and it is perfectly legal to copy and recopy that CD, installing to an entire fleet of computers. Because it's Debian based, adding or upgrading applications is as simple as apt-get.

You can expect a full Knoppix install to take about 25 minutes on a modern computer. Most of this time is unattended, so you can go on with your other work. When you need an operating system right away, Knoppix is ideal.


Disclaimer

Obviously, you use this document at your own risk. I am not responsible for any damage or injury caused by your use of this document, or caused by errors and/or omissions in this document. If that's not acceptable to you, you may not use this document. By using this document you are accepting this disclaimer.

Installing Knoppix

These instructions were written for Knoppix 3.6. Before describing the installation, there's one principle that requires understanding -- a Knoppix hard disk installation can have only those capabilities that existed when you first booted the CD. In other words, if there is no networking when you boot the CD (perhaps because the local DHCP server was down), the hard disk install will not have networking, even if you fix the DHCP server.

Likewise, if there was no sound upon booting the CD, the hardware install won't have sound, even if you insert a sound card.

Knoppix is Linux, so of course you can post-configure a network or sound. However, such post configuration is time consuming. The right way to use Knoppix is to make sure all desired features are present in your CD boot, before beginning your hard disk installation.

Installation involves two, or possibly three steps:
  1. Boot to CD
  2. Install to hard disk
  3. Post installation configuration

Boot to CD

Make sure the computer has a working network connection, and make sure that network connection has a DHCP server on it. A Knoppix CD boot obtains its IP address exclusively via DHCP, so if there's no DHCP server, there will be no networking. Hard disk installs don't have this limitation -- you can set up fixed IP addresses in the post installation phase.
Place your Knoppix CD in the CD drive, reboot, set the Bios to boot off the CD before the hard drive, and let it boot. Knoppix detects all hardware, and comes up in a GUI screen (typically KDE).

Once it's booted, test all features:
If anything doesn't work, fix it before installing to the hard disk.

Install to hard disk

Press the Ctrl+Alt+F2 keystroke combination to get a console. In Knoppix systems booted from the Knoppix CD, such a console is root. Issue the following command:
knoppix-installer
One of two things will happen: Either you'll get a menu of six items, the first of which is "configure installation", or you will be asked to partition the drive. If you're asked to partition the drive, the cfdisk program is called to assist you. Unfortunately, it is likely that the installer won't recognize a valid partitioning setup, thereby denying you the six choice installation menu. The documented way to get past this problem is to perform the installation with the following command:
IGNORE_CHECK=1 sudo knopix-installer
Another way is to either install another distro (waste of time), or format the partitions (mkfs.ext2 and mkswap followd by swapon). Once you get the installation menu, you can continue.

Partitioning

Knoppix installs itself to a single partition. This behavior is right in line with a low TCO  operating system. You don't want to come back later and need to resize partitions, when in fact your disk has excess capacity.

Therefore, make the first partition (/dev/hda1 or whatever) big enough to hold the operating system and expected data. In fact, a case can be made for creating a swap partition plus single partition encompassing the entire rest of the hard disk. This is certainly the easiest way to do things, and assures you that if the user outgrows his partition, he will have also outgrown his entire hard disk.

On the other hand, many of us prefer separate partitions for data (especially /home). To do that, create the future /home partition, but ignore it during the install. You can repartition in the post install, by copying the home directories to that partition, and then modifying /etc/fstab to mount the new home partition.

Post installation configuration

Switching Languages

Users you add in post installation often default to German, in which case you have a catch 22 -- a buried shovel. If only you could read the menu items, you could configure for English, and if only you could configure for English, you could read the menu items. If you have a German language user, the following set of two choices from the start menu should bring you to a point where it's obvious how to switch languages:
On the screen that pops up, choose United States and English, and you're all set.

Knoppix as an Investigational Tool

Before your repair a non-booting system, you need to understand it. Rescue CD's such as the Red Hat Installer and the old Linuxcare CD's don't make such investigation easy. Knoppix does.

Knoppix' default boot is GUI mode. The desktop contains an icon for every partition in the machine. Single-clicking any of these partitions brings up its contents in a file manager so you can instantly deduce its normal mountpoint. Write down each partition device and its mountpoint so that you have the necessary information when you do the actual repair.

You might want to look at some configuration files. And naturally you'll want to browse the logs. Finally, check out the "files" in the /proc directory, especially /proc/meminfo and /proc/partitions.

If there was a question about features like sound and video, check whether they work in Knoppix. If so, copy their configuration files to a place on one of the system's partitions.

Once your investigation's complete, it's time to bust in and take control of the machine.

Backing Up from the Knoppix Environment

In many cases, your first responsibility is to protect the data on a no-boot computer. Boot to your Knoppix CD. and take measures to copy the data off the computer.

By far the easiest way is to copy the data to a CD. This is a great alternative, but there are several requirements:
  1. The computer must have a CD burner (or you must be willing to install one)
  2. The computer must have a partition, that can be mounted read/write, that has enough space to hold image files

Backing Up to CD

To back up to a CD, follow these instructions:
Assuming you have a partition you can mount writeable, you can use tar, gzip, mkisofs and cdrecord to record the CD. This has the advantage of better verification and also compression, meaning you can get more on a single CD. But it involves more thinking, and in tense situations, you might want to go the brainless route.

Network Backups

If you can't back up to CDROM, back up via the network. If necessary, install a network card in the no-boot computer, and Knoppix will find and use it. The network card should be fast (minimum 100Mbps) because of the huge data amounts. Likewise, all wiring, hubs or switches, and the network card on the destination computer should support the high speed.

There's no reason why the no-boot computer or the destination computer should be on the LAN. You could hook them together with two network cables and a hub, or even a crossover network cable (although that reduces troubleshooting test points).

The destination computer must have a partition with enough room to hold the backup, and it must have a DHCP server to give the Knoppix booted computer an address. Of course, if you're connecting to the destination computer through the LAN, any DHCP server on the LAN can give the Knoppix booted computer an address, but take care that it's in the same subnet as the destination computer.

The destination computer must have an ssh server. Or, if you're doing an NFS transfer, it must have an NFS server and a properly configured /etc/exports file.

Backing Up Via ssh

The easiest way I've found is by using ssh. Assuming the following:
In the preceding circumstances, the following command will back up the former home directory will be backed up to emergency.tgz in the /scratch directory on 192.168.100.4:
tar czf - /mnt/hda4 | ssh myuid@192.168.100.4 'cat > /scratch/emergency.tgz'
The emergency.tgz file will extract files to a mnt/hda4/ directory instead of a /home directory. If it's necessary to restore this data, a mv command can be used to put the data in the right place after extraction.

The preceding example backs up an entire partition. To back up a directory within a partition, just append the directory. For instance, had you wanted to back up /home/myuid only, the argument to the tar command would have been /mnt/hda4/myuid.

Backing Up Via NFS

So far I've not found a way, from a Knoppix booted machine, to successfully mount an exported directory, but I'll continue trying to find one. When I do, network backups will be trivial -- something like this:
tar czf emergency.tgz /mnt/nfs

Huge Backups

The backups mentioned in this article fit on a CD or a spare partition. Sometimes that isn't realistic. In such cases, I imagine the ssh method could be used to write directly to tape. I don't know how to do that, but it's probably not too difficult.

Summary

When a computer becomes unbootable, often your first responsibility is to protect the data on that computer. By booting Knoppix on the unbootable computer, you gain access to its partitions and can copy its data either to CD's, or over the network for disposition on another computer. It's often best to perform this backup action before attempting to restore the computer to bootability.

Busting Back Into a Locked Up Machine

You told yourself not to mess with lilo.conf! But nooooooo, you had to mess with it, run lilo, and reboot. And now you get nothing.

Don't worry, Knoppix to the rescue.

First step is to investigate, as described in Knoppix as an Investigational Tool. Once fully armed with information, use your Knoppix CD to bust back in to even the most locked up systems.

Place the Knoppix CD in the CD drive, shut down the system, set the bios to boot from the CD, and bring the system back up. Now, obtain a root prompt by pressing Ctrl+Alt+F2. Actually, the F2 could be anything between F1 and F4, because those are the four virtual terminals. Ctrl+Alt+F5 houses the GUI, which cannot give you a root prompt. Unlike most distributions, Ctrl+Alt+F2 in Knoppix gives you a root prompt without requiring a password.

At the root prompt, you are the root user, with full access to the system.

First, mount the root partition by its device number. For instance, if the partition mounted as the root directory was /dev/hda2, perform the following command:
mount /dev/hda2 /mnt/hda2
Note that Knoppix creates directories for each partition, under the /mnt directory, so there's no need to create /mnt/hda8. What you do next depends on whether you want to use the Knoppix programs to achieve the repairs, or whether you'd prefer to use the programs of the computer under repair. Your choice depends on many factors:
Use the Knoppix Utilities when...
 Use the underlying system's utilities when...
  • You believe the underlying system's utilities have been compromised (rootkit, etc).
  • You're performing repairs requiring the underlying system's root partition or /usr directory or other important partitions to be unmounted.
  • The Knoppix utilities are easier to use.
  • The underlying system's partitions are so damaged as to be useless in restoring bootability.
  • You find it less confusing to work within the original system's directory structure.
  • You're trying to fix a lilo problem.
  • The underlying utilities are easier to use than the Knoppix utilities.

Using the underlying System's Utilities


Assume the following mounts in the original system:

/dev/hda1
 /boot
/dev/hda2 /
/dev/hda3 /usr

Do the following:

mount /dev/hda2 /mnt/hda2
chroot /mnt/hda2
mount /dev/hda1 /boot
mount /dev/hda3 /usr
You now have a replica of the original filesystem, making creation and modification of config files MUCH easier. This is especially important when configuring lilo.conf, because many aspects of lilo.conf configuration depend on the filesystem structure when lilo is run, not when the system is subsequently booted. In other words, if, in the Knoppix world, your system had completely different mountpoints, you'd need to change those mountpoints within lilo.conf, and then change them back once the system was repaired. Ughhh!

When possible, it's often, but not always easiest using your system's native filesystem to accomplish the repairs.

Always remember to unmount everything before rebooting and attempting to boot the original system. Unmounting guarantees that everything will be written to disk. Do the following: 
umount /dev/hda3
umount /dev/hda1
exit
umount /dev/hda2
The exit command undoes the chroot performed earlier.

With the partitions unmounted, from the Knoppix command prompt, type reboot. The CD will pop out. Remove it, press Enter, and the system will attempt to boot its original operating system.

Using the Knoppix Utilities

Unfortunately, it's not always advisable or even possible to use the native system's utilities. For instance, one or more of the native system's partitions might be so damaged as to be unusable. Or maybe you suspect that you've been rootkitted and don't trust the native system's utilities.

The real showstopper is that if you boot to Knoppix and then chroot to the underlying system's root partition, the functional /proc and /dev special directories are unavailable. You might find contents in the /dev directory, but they're not real devices. Sometimes you can perform /proc and dependent tasks before chrooting. Other times it's better to byte the bullet and decline to chroot. Except in special cases such as lilo.conf, it's not difficult.

Once again, assume the following mounts in the original system:

/dev/hda1
 /boot
/dev/hda2 /
/dev/hda3 /usr

First, perform actions requiring unmounted partitions. The tune2fs, fsck and e2fsck commands come to mind. Then mount the drives:
mount /dev/hda1 /mnt/hda1
mount /dev/hda2 /mnt/hda2
mount /dev/hda3 /mnt/hda3

Now you can work on individual files and run programs. Perhaps you need to copy files onto the computer. This is particularly true if you blew a computer compile and now must get it back. Don't forget that with modular kernels, the original /lib/modules/version_number directory must be restored. Perhaps the best bet is to compile a monolithic kernel on another machine, place it and its associated initrd file on the blown machine, modify grub.conf, run grub_install, and reboot.

Always remember to unmount everything before rebooting and attempting to boot the original system. Unmounting guarantees that everything will be written to disk. Do the following: 

umount /dev/hda3
umount /dev/hda2
umount /dev/hda1

With the partitions unmounted, from the Knoppix command prompt, type reboot. The CD will pop out. Remove it, press Enter, and the system will attempt to boot its original operating system.

When Things Go Wrong

"Does not boot" problems are seldom simple. They're usually caused by system level problems -- often arcane ones. Here are some troubleshooting tips:

Summary

When things go wrong, you need Knoppix. A Knoppix CD can allow you to boot an unbootable computer, salvage and transfer its data, and then fix whatever is preventing bootup.

See also: [ Linux Library | Knoppix Knowhow | Troubleshooters.Com | Email Steve Litt | Copyright Notice ]

Copyright (C)2003 by Steve Litt. -- Legal