Hack 21 Create Persistent Knoppix Settings

Knoppix has the capability of saving changes you have made during your session to floppies, USB drives, or other removable media. Use this ability to create a Knoppix setup that you can take to any computer.

One of the great things about Knoppix is that it all resides on a single CD, so you can take the same desktop environment and programs with you to any accessible computer. One problem, however, is that a CD is read-only media, so any configuration changes you make or any special settings you might change to get Knoppix to work on your hardware are lost the moment you shut down the computer. If you have a USB drive, a floppy drive, or some other writable media, Knoppix has automated the process of keeping changes you make to Knoppix persistent across reboots. You even have the option of saving your entire /home directory if you want, which means you can take your data with you too.

3.2.1 Save Settings

To save all of your changes, click K MenuKNOPPIXConfigureSave Knoppix configuration or run /usr/sbin/saveconfig in a console. There are a number of settings that Knoppix can save. The different types of settings you can choose from are:

Personal configuration (desktop, programs)

Select this option to save the configuration files in your home directory. KDE and other Linux programs have standardized the saving of user settings in hidden files and directories, which begin with a period and are commonly referred to as dot files. So this option saves any theme or color changes you have made for your desktop, any settings changes made for any program (so, for instance, this would save your web browser bookmarks and your email settings), and any other configuration settings that are stored in these hidden files.

All files on the desktop

This option doesn't save settings per se but instead backs up the full /home/knoppix/Desktop directory, so any files you have saved on the desktop will still be there the next time you reboot if this option is checked. Use this option in lieu of saving the entire home directory, which is described below, if you just have a few files on the desktop that you wish to save and don't particularly care about keeping configuration changes.

Network settings (LAN, Modem ISDN, ADSL)

Select this option to save special network-specific directories and settings stored under /etc so they will be reloaded the next time the machine is booted. Choose this option if you had to make any special changes to your network settings, such as set up a wireless, PPPoE, or dial-up connection.

Graphics subsystem settings (XF86Config)

This option saves the configuration files under /etc/X11 and reloads them on reboot. Check this option to save direct edits you have made to your XF86Config file to get your graphics environment to load.

Other system configuration (printer, etc.)

This option saves some other miscellaneous configuration settings, including those for printers and other peripherals.

Saveconfig's default is to select all these options except for saving desktop files. If you plan to use Knoppix on many machines with different hardware and network configurations, you might want to just select the first option, "Personal configuration," so that desktop, data, and program settings will be saved, but network and graphics settings will be detected on each new machine you come to.

After you select which settings to save and click OK, Knoppix provides a list of all the available writable media you can store your settings to. This includes any hard drives on your system, floppy drives, and any USB or other removable storage currently connected. Select the device to save to, and Knoppix will back up your settings to that device.

Knoppix stores its configuration settings in the root directory of the device in a bzipped tar file called configs.tbz, along with a script that Knoppix runs to restore this configuration called knoppix.sh. To examine just which files Knoppix has saved, click on configs.tbz in a file manager (Konqueror automatically displays the contents of archives) or run the following command in a console:

knoppix@ttyp0[knoppix]$ tar tvfj configs.tbz

The size of the file varies depending on how many program settings are being saved and, if you are saving your desktop, the size of any files stored there.

Now that you have your settings and data saved, you need some way to use what you've saved in subsequent boots. This is where myconfig comes in. If you have saved your settings to a removable USB drive at /dev/sda1, boot with the cheat code:

myconfig=/dev/sda1

If you don't know which device the settings are stored on, then boot with:

myconfig=scan

This command instructs Knoppix to scan for your settings on all devices it finds. In general, it is easier to just use the scan option unless you have saved settings at different times on different devices, in which case you may prefer to explicitly tell Knoppix which device to use.

After Knoppix boots, it then runs the knoppix.sh script it created when you backed up your settings and extracts the files from configs.tgz.

Remember that if you make any new changes that you would like to save, you must run the saveconfig script again.

3.2.2 Save Your Home Directory

Through the use of the mkpersistenthome script and the home cheat code, Knoppix also supports saving your entire home directory to an image that can be restored in later boots. The mkpersistenthome script backs up the complete /home/knoppix directory with all of its hidden and unhidden files, including the desktop. This makes it different from the saveconfig script, which just backs up the hidden configuration files and the desktop. Another difference with this method is that creating a persistent home directory means that Knoppix mounts this new image as the home directory, so that as long as you pass the home cheat code at boot, any changes or new files in the home directory are still changed the next time you reboot without the need to run the script again.

To create the persistent home directory image, run K MenuKNOPPIXConfigureCreate a persistent KNOPPIX home directory or from a console run:

knoppix@ttyp0[knoppix]$ /usr/sbin/mkpersistenthome

The execution of this script is similar to the saveconfig script. When run, it presents you with a list of detected drives on which to create the persistent home directory. One main difference is that after you choose your drive, you have the potentially dangerous option to format the drive and use the entire drive for the home directory. The safest choice is to tell Knoppix to create a loopback file on the device that it will save to. A loopback file is an entire filesystem contained within a single file, like a CD image. Loopback files can be formatted and mounted just as though they were full filesystems.

You must also choose a size for the loopback file. The size of your loopback file depends greatly on how many extra files you plan to store. See how much space you are currently using for your home directory by typing the following command:

knoppix@ttyp0[knoppix]$ du -sh ~

12M     /home/knoppix

Keep in mind that this loopback file does not grow even if there is more free space on the drive. Therefore, choose a file size based on how much space you think you will need in the future, not just how much you need now. Otherwise, when you need more space, you will have to create a brand-new persistent home directory and copy your files over. To resize the image to size megabytes, type:

knoppix@ttyp0[knoppix]$ resize2fs knoppix.img size

M

After configuring the loopback file, Knoppix creates and formats the loopback file and then copies the full home directory to it.

When the script finishes, you should see a knoppix.img file on your storage device. To view the contents of the file, mount it with the following command:

knoppix@ttyp0[knoppix]$ mkdir ~/temp

knoppix@ttyp0[knoppix]$ sudo mount -o loop /mnt/sda1

/knoppix.img ~/temp

Replace /mnt/sda1 with the path to your Knoppix image, then see the contents of the file at /home/knoppix/temp.

To tell Knoppix to use the loopback file for your home directory at boot, use the home cheat code. This cheat code works just like the myconfig cheat code covered earlier in this hack. You can either pass it a specific device that contains knoppix.img or boot with home=scan for Knoppix to scan all available drives for knoppix.img. For example, to use a persistent home directory created in /mnt/sda1/knoppix.img, boot with:

home=/mnt/sda1/knoppix.img

If you have a Linux partition available on your system and are willing to add the Knoppix home directory to it, you can also create a full Knoppix home directory without reformatting a drive or being limited by the space to which you have assigned an image. This method is particularly useful to add an extra directory to your desktop's home directory just for use by Knoppix. On the underlying Linux system, it looks just like a new user named knoppix has been added.

First, choose the partition you wish to use and make sure that it is writable—changing read/write mode is covered in [Hack #10] . For these examples, I use /mnt/hda3, which contains my regular Linux home directories on this system. To create the new home directory and make sure that the knoppix user owns it, open a terminal and type:

knoppix@ttyp0[knoppix]$ sudo mkdir /mnt/hda3

/knoppix

knoppix@ttyp0[knoppix]$ sudo chown knoppix:knoppix /mnt/hda3

/knoppix

To copy your Knoppix home directory, run:

knoppix@ttyp0[knoppix]$ rsync -av /home/knoppix/ /mnt/hda3

/knoppix/

To use this directory the next time you boot, use the home cheat code, but make sure to pass it the path to this new home directory. In this example, type:

home=/dev/hda3

/knoppix

Now you can have a special Knoppix home directory along with all of your other user accounts. Similar to other persistent home directory methods, this method uses this directory in place of a ramdisk for /home/knoppix, so any changes you make or files you create are always saved—without running any extra commands.

Knoppix's persistent cheat codes are especially handy if you use Knoppix frequently, as it bypasses many of the disadvantages of booting from a read-only media and allows you to save changes you have made. Combine these persistent settings with a small USB key drive, and your settings and files can follow you to any computer with a CD-ROM drive and a USB port.