[ 6 January 1998

[ 6 January 1998
The Linux JAZ-drive mini-HOWTO is not being maintained by
the author any more. If you are interested in maintaining the
JAZ-drive mini-HOWTO, please get in touch with me at
<[email protected]>. ]

JAZ-drive mini-HOWTO
Bob Willmot, [email protected]
v1.6, 04 June 1997

This HOWTO covers the configuration and use of the Iomega Jaz drive
under Linux and software tools available for the drive.

1. Introduction

The Iomega Jaz drive is a removable media disk drive whose disks
have a capacity of 1021 megabytes. It is currently available in internal
and external SCSI configurations. Iomega plans to release an internal
IDE version.

This document describes how to use the Jaz drive with Linux. Since
this is a SCSI device, it is important for you to read the Drew Eckhardt's
SCSI HOWTO as well.
http://sunsite.unc.edu/pub/Linux/docs/HOWTO/SCSI-HOWTO

I'd like to thank the following people for their contributions and info
they've provived.

* Grant Gunther, [email protected]
* Tom Poindexter, [email protected]
* Todd Woods, [email protected]
* Richard B. Melrose, [email protected]
* Phil Howard, [email protected]
* Rick Niess, [email protected]

If you have any comments/suggestions/corrections please send them to:
Bob Willmot, [email protected]

2. The Jaz disks

The Jaz disks (cartridges) resemble a stack of three 3.5" floppy disks
that hold 1GB of data.

The drive has a motorized mechanism that can eject the disk via
a pushbutton on the from of the drive or through software (see
below on info about the jaztools Linux software)

2.1. The Jaz Jet host adapter

Iomega markets a SCSI host adapter under the name Jaz Jet.

Aparently there are currently two versions of this controller available,
based on two difference SCSI chipsets.

One is based on the Adaptec 7800 family of adapters, and is compatible
with the 2930/2940 host adapters. Linux 2.0 supports this adapter with
the aic7xxx driver. (this driver was introduced in the 1.3.? version of
the kernel).

The other adapter is based on the Advanced Systems chipset. At boot time
the board gives a message like
Jaz Jet PCI SCSI adapter Copyright Advanced Systems 1996
Compile the kernel with the CONFIG_SCSI_ADVANSYS variable set.

3. Configuring a kernel for the Jaz drive

To use the Jaz drive with Linux, you must have a kernel configured
for you SCSI adapter.

Info on building the kernel can be found in the /usr/src/linux/README
file, or in /usr/src/linux/Documentation/ directory for the 2.x kernels.

Also check out Brian Ward's Kernel-HOWTO
http://sunsite.unc.edu/pub/Linux/docs/HOWTO/Kernel-HOWTO

4. Identifying the drive at boot time

When your system boots it should display information about your adapter,
and any disks that arre attaced to the drive.

Boot messages will vary depending on your SCSI adapter and are logged
to the /var/log/messages (or /var/adm/messages) file. You can also
'replay' these messages from the command prompt with the dmesg command.

Here's the kernel booting output from a 2.0.10 kernel with an
Adaptec 2940 controller:

aic7xxx: BurstLen = 8 DWDs, Latency Timer = 64 PCLKS
aic7xxx: AHA-2940 Ultra Rev B.
aic7xxx: devconfig = 0x580.
aic7xxx: Reading SEEPROM...done.
aic7xxx: Extended translation enabled.
aic7xxx: Using 16 SCB's after checking for SCB memory.
AHA-2940 Ultra (PCI-bus):
irq 11
bus release time 40 bclks
data fifo threshold 100%
SCSI CHANNEL A:
scsi id 7
scsi selection timeout 256 ms
scsi bus reset at power-on enabled
scsi bus parity enabled
scsi bus termination (low byte) enabled
aic7xxx: Downloading sequencer code...done.
aic7xxx: Resetting the SCSI bus...done.
scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 3.2/3.1/3.0
scsi : 1 host.
aic7xxx: Scanning channel A for devices.
aic7xxx: Target 4, channel A, now synchronous at 10.0MHz, offset(0xf).
Vendor: iomega Model: jaz 1GB Rev: G.60
Type: Direct-Access ANSI SCSI revision: 02
Detected scsi removable disk sda at scsi0, channel 0, id 4, lun 0
scsi : detected 1 SCSI disk total.
SCSI device sda: hdwr sector= 512 bytes. Sectors= 2091050 [1021 MB] [1.0 GB]
sda: Write Protect is off

In the above log note the raw scsi device name (sda,sdb, etc).
You'll need to use this to access the disk later.

If these lines do not appear, then something is misconfigured in your
hardware or in the kernel.

If the scsi0: line does not appear, then you have not configured your
host adapter and its driver correctly. Some drivers will give you a
hint about what is wrong. If your drive is not detected, you
probably have a cable problem. If a drive name is not assigned, you
probably forgot to include SCSI disk support when you built the
kernel.

Check the README files in drivers/scsi and the SCSI HOWTO for other
debugging hints.

4.2. Fdisk, mke2fs, mount, etc.

Once you know the drive name for your Jaz drive, you are set. You can
manipulate the drive with the normal Linux disk management commands,
fdisk, mke2fs, mount etc.

Refer to the manual pages for these programs.

4.2.1. An existing DOS formatted disk

Disks factory formatted from Iomega are partitioned with a single
partition (for some unknown reason they use the 4th partition).

You can mount this disk (assuming your jaz disk is the raw SCSI device
sda) with the commands

mkdir /jaz
mount -t msdos /dev/sda4 /jaz

Or if you are using the 2.0 kernels and have compiled the kernel with
support for the Win95 VFAT support you can mount it with

mkdir /jaz
mount -t vfat /dev/sda4 /jaz

(this will allow you to read/write long filenames)

Files from the disk will appear in /jaz. While the disk is
mounted, you will not be able to eject it.

To unmount the drive you can issue the command:

umount /dev/sda4

Once you've made the /jaz mount point - you don't need to do it again,
(also make sure your not in the /jaz dir when you try to umount the
drive)

4.2.2. Re-format as a native Linux disk

If you want to erase a Jaz disk and make a Linux native file system on
it. you should use fdisk on the entire disk:

fdisk /dev/sda

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

Format the partition

mke2fs /dev/sda1

(The 1 is the number that you gave this partition in fdisk). Now you
can mount the disk:

mount -t ext2 /dev/sda1 /jaz

(re-using that mount point we created before).

4.2.3. The Jaz Tools disk

There is some extra work to be done if you want to use the disk that
comes with the Jaz drive. As shipped, the software controlled write
protection is enabled.

There are two options here: you can unlock the disk under DOS or
Windows with the "reclaime.exe" program (or by installing the tools
from the setup program) or you can unlock the disk with my jaztools
program (see section 5) with the command

jaztool /dev/sda rw

(adjust the /dev/sda to your appropriate SCSI device) and when prompted
for the password enter

APlaceForYourStuff

5. jaztools

A native Linux program to support some of Iomega's special features
(including software controlled ejection and write protection)
is available at

http://www.cnct.com/~bwillmot/jaztool/

There should be a new version of jaztool available shortly that will
contain a GUI interface and support drive scanning and automated
mounting and unmounting of disks.

6. Frequently asked questions

6.1. I can only mount the Jaz tools disk read-only

The tools disk is shipped in a special password-protected read-only
mode. To unlock the disk run the "reclaim.exe" program under
DOS or Windows or use the native linix jaztools program (see section 5)
with the command

jaztool /dev/sda rw

(adjust the /dev/sda to your appropriate SCSI device) and when prompted
for the password enter

APlaceForYourStuff

6.2. The Jaz locks my system after it spins down ?

I have a feeling that this may be related to the Jaz firmware. Anyone
who has this problem, let me know what Revision your drive is. To determine
Jaz rev check the output of the /etc/dmesg program for some lines like:

scsi0: Target 4, channel A, now synchronous at 10.0MHz, offset 15.
Vendor: iomega Model: jaz 1GB Rev: G.60
Type: Direct-Access ANSI SCSI revision: 02

This apparently happens only under one specific circumstance that the
average Linux user is unlikely to encounter. When the Jaz drive has a
partition/filesystem mounted, the drive spins down with the filesystem
still mounted, and an attempt is made while the drive is still idle to
read from the block device. It appers that Linux attempts to read the MBR
again to restablish the partitions, but somehow this fails _sometimes_ and
leaves the device in an apparently busy state. Both the kernel read for
the MBR and the process device read will fail and this failure may be due
to a lockout or busy status. In this state it thinks it is still reading
even though no I/O is pending or operating. I've had this happen mostly when
block device reading the MBR itself

6.3. Can I boot from the Jaz drive ?

The Jaz drive can select any SCSI target ID from 0-6.

If the Jaz drive co-exists with other SCSI harddrives, most BIOSes will
want to boot the lowest SCSI id that is a disk. Some detected and skip
removeable devices like the Jaz.

If the Jaz drive co-exists with IDE harddrives, nearly every BIOS will
want to boot the first IDE harddrive. Some BIOSes will allow removing
the first IDE device from the configuration and will assign the first
SCSI device as the boot device (Bios 0x80). Others may require removing
all IDE devices from configuration. Still others may require detaching
the IDE drives physically or disabling the IDE interface.

6.4. Why does Iomega use partition number 4 ?

Partition 4 is the default partition used by Macintosh.

On a Mac, the first partition is reserved for boot info, the second for
system info, the third is the resource fork, and the fourth is the data
fork.

Anyway, PCs and most other systems can deal with having to work on the
4th partition whereas the Mac can't deal with anything else. Iomega
sends all their preformatted media with partition 4 used so that both
PC's and Macs can read them and everyone avoids a big compatibility
headache. (PCs with mac-disk-reading software usually expect the data
to be on partition 4)

6.5. How can I have the disk mounted at boot time ?

All you need to do is to add a line to your /etc/fstab file. For
instance, if you will always have a DOS disk in the drive when you
boot, you could put

/dev/sda4 /jaz msdos defaults 0 0

in the fstab. Depending on your distribution, the initialization
scripts might try to run fsck on partitions listed in your fstab. Be
aware that this could cause problems if you forget to put the disk in
the drive when you boot, or have the wrong disk there.

To eliminate these problems you can add a separate mount command in
/etc/rc.d/rc.local to mount the Jaz drive. This will avoid problems
with the standard "mount -a" that takes place when there is no cartridge
in the drive.

6.6. What happens if there is no disk inserted when I boot ?

The kernel will try to read the partition table, but the operation
will (eventually) time out.

When you change disks, it is a good idea always to use fsck to
check the partition structure on the new disk.

The BIOS on some SCSI host adapters will attempt to read the partition
table on your disk during the system boot. If you cannot disable this
check, you may be forced always to boot with a disk in the drive.

6.7. How can I make my Jaz cartridge self-bootable (assuming my BIOS
is set up to allow it?)

The Jaz drive/cartridge makes an excellent ERD (Emergency Repair Disk).
It's also fun to be able to just pop in some new Linux system or to try
Linux on someone else's Jaz-equipped machine.

You could just follow the install procedure for your favorite distribution
with the Jaz drive being the only drive on the system.

However if you want to do an "install" from your running system, you can
often succeed in "building" a self-bootable system on a Jaz cartridge.

Step 1 - partition the drive and make the filesystems. You probably
need to have a swap partition, too, but if you have lots of RAM then maybe
not. Mount the new root as /jaz and any additional partitions within that
directory as appropriate.

Step 2 - copy all the files into place. Be sure all the /dev files
are copied. Be sure all permissions, ownership and groupids are retained.

Step 3 - modify the files on the Jaz cartridge to suit the circumstances
of booting from it. In particular be sure to change /jaz/etc/fstab to mount
the Jaz cartridge partition(s) as appropriate. Also change /jaz/etc/lilo.conf
to match as well.

Step 4 - there are two alternatives:

A: make a kernel image floppy and use "rdev" to make it mount the Jaz
cartridge as root. Boot from the floppy when ready the first time
then run lilo to make the Jaz MBR bootable.

B: you can run lilo from your non-Jaz root running system to install the
bootable MBR on the Jaz cartridge. Add these lines (change "1" to your
root partition number and "sda" to your Jaz device name as appropriate)
to your /jaz/etc/lilo.conf file before the first system definition:

drive = /dev/sda1
bios = 0x80

When you are all ready to install the Jaz MBR, you run lilo with the
-r option to make it operate within the /jaz tree as if it is /. The
command looks like:

lilo -r /jaz

Normally lilo searches for what the bios device number of the boot
device will be at boot time. This needs to be overridden since the
Jaz drive is not currently the bootable one. The 2 added lines do
this.

There will be a number of error messages output by lilo and the kernel.
Lilo is warning you there may be problems which will not be in this
case. The kernel reports problems related to /dev/hdc which are due
to probes for devices that lilo is doing trying to discover some things.
Lilo tries to make a device node for the old major/minor code for "hdc"
and the kernel is recognizing the attempt as an error. These messages
can be ignored. Watch the Jaz drive light to see it being written to.

At this point your Jaz drive should be bootable.

7. Getting more current information

The most up-to-date version of this mini-HOWTO can be found at:

http://www.cnct.com/~bwillmot/jaztool/

Iomega's web pages are at

http://www.iomega.com/