Hack 41 Create an Emergency File Server

When files need to be transferred quickly over the network, Knoppix can serve as a quick makeshift file server.

There are many different occasions that might call for creating an emergency file server. For instance, you might have a file server with multiple drives that has suffered hard-disk failure on the root drive. All of the hard disks that have shared data are fine, but you need to still serve files while waiting on the replacement drive. This is the perfect environment for anyone wanting to learn how to configure Samba or start up a quick temporary file server. For experienced systems administrators, this makes it easy to share all the drives on an infected system for a quick virus scan by a centralized corporate virus scanner while the infected OS is shut down. You can even connect a spare machine to a printer, boot Knoppix, and quickly configure a makeshift network printer server.

Knoppix includes a nice GUI configuration utility to configure Samba (the Linux SMB file server). You aren't required to use the Knoppix Samba utility to set up a file server. If you already know which kind of configuration you want, simply edit /etc/samba/smb.conf directly, and then run this command to start the Samba process:

knoppix@ttyp0[knoppix]$ sudo /etc/init.d/samba start

To use the Knoppix-provided Samba configuration utility, click K MenuKNOPPIXServicesStart Samba Server. Each time you run this script, it wipes out the previous Samba configuration, so don't run this script if you have made changes to smb.conf that you want to keep. This program prompts you to choose a password to assign to the knoppix user if there isn't already one, because Knoppix's default behavior requires a username and password to access any shares it creates.

After it confirms your password, Knoppix asks you whether you want to export all your hard drives so that remote machines can access them. If you answer "no" to this question, the script creates an smb.conf file that shares your home directory and any printers that you have previously configured on the system. If you answer "yes" to this question, the script adds shares for all hard drives and CD-ROM drives that Knoppix has detected, and automatically mounts the devices for you as they are accessed. Once you click "yes" or "no," the script creates the smb.conf file and starts Samba.

If you only want to share all of the drives on your system as read-only over the network, then you are finished. By default, the share shows up in the WORKGROUP workgroup as a machine named KNOPPIX, and if you have shared all of the drives on your system, they appear with the same names they were previously assigned on your desktop, such as hda1. You can find the configuration for each drive at the bottom of the /etc/samba/smb.conf :

[hda1]

    comment = /mnt/hda1

    browseable = yes

    path = /mnt/hda1

    writeable = yes

    preexec = /bin/mount /mnt/hda1

    postexec = /bin/umount /mnt/hda1

These shares all require that you log in with the username knoppix and the password you created for the knoppix account. Then Knoppix automatically mounts the drive when you access it and unmounts it when you are finished. Notice that by default, Samba is configured to allow writing to the drives, but Knoppix automatically mounts all drives read-only, so it overrides this, and you are still able to read from the drives. To allow write access to a drive, modify the preexec line in smb.conf to read:

preexec = sudo /bin/mount -o rw /mnt/hda1

and replace /mnt/hda1 with the drive you are configuring. To allow anyone to access the share without requiring a password, add the following line to the share's configuration:

guest ok = yes

In general, you do not need to restart Samba for share level changes to take effect; however, changes you make to the global configuration (under the [global] header) require you to restart Samba.

To share something entirely different from the hard drives, add new shares to the default configuration. It doesn't matter which script option you chose earlier, just add the new configuration to the end of the file. The following example creates a new directory called share under the home directory knoppix and configures it as a guest share under Samba. First, create the share directory:

knoppix@ttyp0[knoppix]$ mkdir /home/knoppix/share

Then edit /etc/samba/smb.conf as root, and add the following lines:

[share]

    comment = Knoppix share

    browseable = yes

    path = /home/knoppix/share

    writeable = yes

    guest ok = yes

Once you save your changes, the new share immediately appears, and anyone is able to view, add, and delete files in that directory. Keep in mind that this share is running off of your home directory that is in a ramdisk by default. The size of files stored here are limited by RAM, so for storing large files, you want to configure a share on the system's hard drives.

Remember that each time you run the Knoppix Samba configuration script, it creates a new smb.conf, and any manual changes are lost.