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Once you are logged in via SSH (or telnet), you have to run the Linux/390 standard
dasdfmt and fdasd programs to format and partition your DASD volumes.
At first glance it looks a little scary, but it's really quite simple.
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Starting dasdfmt
For Linux/390 systems, the rules are pretty simple. Format everything with a blocksize
of 4096, and create at least one partition per DASD volume or minidisk. The device
names you will be formatting will depend on how many DASD device numbers you told the
startup script. The devices will be named like this:
/dev/dasda
/dev/dasdb
/dev/dasdc
etc.
Formatting an entire 3390-3 (or larger) volume can take quite a while, so start up the
dasdfmt command and go do something else while it is running:
dasdfmt -b 4096 -f /dev/dasda
Dasdfmt will warn you about what it is going to do, and ask you to confirm that by
typing in "yes," unless you specify the "-y" switch. If you do, dasdfmt will not ask
for confirmation, and just format the device. So, make sure you specify the right
device number if you want to use "-y."
dasdfmt -b 4096 -y -f /dev/dasda
Repeat this for every DASD volume or minidisk you want your Linux/390 system to use,
and then move on to the partitioning step.
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Starting fdasd
Once your DASD has been formatted, then you have to create at least one, and a maximum
of three partitions on each volume or minidisk. The limit of three is different from
that on Intel Linux, where you can have up to 4 primary paritions, or 3 primary
partitions and one extended partition that can hold a large number of logical
partitions.
The fdasd command is very similar to the fdisk command. When invoked, it gives you a
list of all the possible sub-commands:
fdasd /dev/dasda
reading volume label: VOL1
reading vtoc : ok
Command action
m print this menu
p print the partition table
n add a new partition
d delete a partition
v change volume serial
t change partition type
r re-create VTOC and delete all partitions
u re-create VTOC re-using existing partition sizes
s show mapping (partition number - data set name)
q quit without saving changes
w write table to disk and exit
Command (m for help):
To create the required one partition, and have it use all the available space, simply
type "n," and hit the enter key twice in response to the prompts for "First track," and
"Last track." Type the "w" command to write out the partition table and exit the fdasd
command. Repeat this for every DASD volume or minidisk you have defined.
If you are going to be using real DASD for your swap volume/partition, remember to
use the "t" sub-command to change the parition type to "Linux swap" instead of "Linux
native." This will allow the installation routines to properly detect it and set it up
for you automatically. If you are going to be using the xpram device driver, or z/VM
V-disk, this is not necessary (or possible), since dasdfmt and fdasd only work with
ECKD devices, and not DIAG or FBA ones.
The installation routines will detect all DIAG and FBA devices, and present
them to you as potential candidates for swap devices. If you have DIAG or FBA devices
that you do not want used for swap, simply de-select them when presented with the
list.
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