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4. Using a Jaz Disk

4.1 DOS Formatted Disks

Jaz disks come pre-formatted from Iomega with a single partition using the DOS FAT16 file system. The single partition is usually the 4th disk partition (for Mac compatibility - the Mac requires data to be on the 4th partition, but the PC doesn't care which partition data is on).

Linux is perfectly happy reading and writing a FAT16 file system, so you can use the disk as is. In order to use the disk, you need to mount it, so the first thing you need to do is create a mount point. For this document, we'll mount all our DOS Jaz drives under /dos_jaz, so let's create that mount point (you'll need to be root for most of this stuff). You'll only need to do this once:

mkdir /dos_jaz

In a previous section, I mentioned you'd need to remember the Jaz drive's raw SCSI device name. You need that now. If your drive is /dev/sda then all these examples will work for you. If not, you'll need to replace "sda" with the device ID of your Jaz drive. Since you need to issue these commands as root, you'll want to be sure you have the correct names.

If you have a 2.0 kernel, or have added VFAT support, you can mount the Jaz disk this way, and have long filenames under FAT16:

mount -t vfat /dev/sda4 /dos_jaz

Note that although VFAT allows you to use long filenames, those filenames are still case in-sensitive, and although 'ls' lists permissions, you can't actually change permissions on any of the files.

If the "vfat" format is not recognized by the mount command, then you'll use this command to mount the Jaz disk:

mount -t msdos /dev/sda4 /dos_jaz

Once you have issued either of the mount commands, files from the disk will appear under the /dos_jaz directory. While the disk is mounted, you will not be able to eject it.

When you are done with the disk, you can unmount it with the command:

umount /dos_jaz

Once unmounted, you can press the button on the front of the drive to eject the cartridge.

4.2 Repartitioned DOS Jaz Disks

Since a Jaz disk is simply a disk, it can be repartitioned and reformatted like a fixed disk. If this is done, you need to know which partition numbers were used during repartitioning to be able to mount the disk.

For instance, if the partition table was wiped, and a single new partition was created as the first partition, the two mount commands from the previous section would be:

mount -t vfat /dev/sda1 /dos_jaz

and

mount -t msdos /dev/sda1 /dos_jaz

4.3 Linux-Native Jaz Disks

Linux-Native Jaz disks allow files to be stored with standard Unix permissions and case-sensitive filenames. The only drawback to Linux-Native disks is that they can no longer be used on DOS/Windows machines.

A Jaz disk looks the same as a hard drive to Linux, so for those of you familiar with the Linux disk management tools, none of the following will be a surprise.

If you want to erase a Jaz disk and make a Linux native file system on it, you use fdisk on the entire disk. Please be very careful using fdisk, especially if you have a SCSI hard drive - we wouldn't want to have any "accidents". :-) In particular, make sure you are operating on the correct device before making changes. In most cases, you'll use:

fdisk /dev/sda

and delete the existing partitions (with the d command). Then create a new partition with the n command, make it primary partition number 1 (using all the cylinders), use w to write the partition table to disk, and quit with q.

Once the partition has been created, format it with:

mke2fs /dev/sda1

(The 1 is the number that you gave this partition in fdisk). I prefer to create a separate mount point for Linux native Jaz disks, and you'll see why a little later when we talk about the fstab. So let's create that mount point now, and then mount the disk:

mkdir /jaz

mount -t ext2 /dev/sda1 /jaz

As usual, when the Jaz disk is mounted, it cannot be ejected. When you're done using the Jaz disk, you unmount it with:

umount /jaz

Once unmounted, you can press the button on the front of the drive to eject the cartridge.

4.4 Checking Linux-Native Jaz Disks

Like your other disk drives, once a Linux Jaz disk has been mounted and unmounted a certain number of times, the system will mark the disk as "dirty". When this happens, you'll get a message like:

Mounting unchecked filesystem, /dev/sda1. Recommend running e2fsck.

Once you see this message, it's a good idea to go ahead and check the disk. The disk must be unmounted in order to check it. Unfortunately, you only get the "dirty" message when you mount it, so you can either check the disk when you're done using it, or unmount it, check it, then re-mount it. Use the following command to check the disk (assuming the partition to be checked is the first one):

e2fsck /dev/sda1

4.5 Using the fstab to Make Things Easier

Up to now, we've had to be root to mount and unmount the Jaz disks, and we've had to type quite a bit to mount the Jaz disks. By adding a couple of entries to the file /etc/fstab, we can make using the Jaz drive much easier.

DOS Format Disks

If you've got preformatted DOS disks, and you've created the /dos_jaz mount point, you can add this line to the file /etc/fstab:

/dev/sda4 /dos_jaz vfat defaults,user,nosuid,noauto 0 0

With this line in the fstab, any user can mount and unmount a DOS-format Jaz cartridge with the following commands:

mount /dos_jaz

umount /dos_jaz

This is because we have told Linux what the Jaz device ID and media type are in the fstab, plus we have given the user option to allow any user to mount and unmount the disk. Naturally, if your Jaz drive is other than sda, you'll need to change that, and this won't work for DOS cartridges that have been repartitioned without another entry in the fstab that uses a separate mount point (e.g. /dos_jaz2).

Linux Format Disks

If you've got Linux formatted disks, and you've created the /jaz mount point, you can add this line to the fstab:

/dev/sda1 /jaz ext2 defaults,user,exec,nosuid,noauto 0 0

With this line in the fstab, any user can mount and unmount a Linux-format Jaz cartridge with the following commands:

mount /jaz

umount /jaz

Once again, we have told Linux what the Jaz device ID and media type are in the fstab, plus we have given the user option to allow any user to mount and unmount the disk. Some system administrators may not wish to have the exec option present, as there are some security risks with letting any user run an executable of unknown origin from the drive, but with the nosuid option present, these risks are minimal.

Automatic Mount at Boot Time

Both of the fstab examples above have the option noauto in them to prevent the disk from being automatically mounted at boot time. In general, this is a good idea because if there is no disk in the drive when the computer boots, or the drive is powered off, it can cause varying amounts of trouble, depending on which SCSI driver you are using.

If you're sure you want to mount the jaz drive at boot time, simply remove the noauto option, and make sure the drive is on, and a cartridge is inserted before booting. Note that you can only have one fstab entry for jaz drive that will auto-mount, or you may encounter the same problems as if there was no cartridge in the drive.

4.6 The Jaz "tools" Disk

With some Jaz drives, the software to run the drive is supplied on a Jaz cartridge instead of on CD-ROM. The "problem" with these disks is that software-controlled write protection is enabled on the disk, so that the user can't wipe the disk until after the tools are installed at least once.

There are several ways you can reclaim the Jaz tools disk:

If you have access to one of the password protection removal programs, all you need is the password that Iomega uses, and it is:

APlaceForYourStuff

Note that capitalization is important.

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