[cobalt-users] HOWTO: Changing partition sizes on a custom OS Restore CD

[Bruce Timberlake <bruce@xxxxxxxxxx>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

(for the archives...)

Original reference from Gerald:
http://list.cobalt.com/pipermail/cobalt-users/2002-July/073547.html

The Partition_Table referred to is in
/nfsroot-x86/bto-sync/production/<release_spec>/installer/release_spec.<product>

For example, on RaQ 4r, it's

/nfsroot-x86/bto-sync/production/3100R_1.155/installer/release_spec.3100R

The relevant bit of the release_spec file looks like:

# This is the partition table for the product
%begin Partition_Table
0,750,83
,158,5
,200,83
,,83
,30,83
,,82
%end Partition_Table

The format of each line in this section is:

Start, Size, ID

The sfdisk command used in the cobalt_install script (found in 
/nfsroot-x86/bto-sync/production/3100R_1.155/installer/) is :

/sbin/sfdisk -f -L -uM

so we're working in megabytes (that's what the -uM switch is for)

Start = MB to start at (first available MB if left blank)
Size = number of MB (all if left blank)
ID = type of partition (Linux, Swap, MSDOS, or other)

First, let's look at a working system (my RaQ 4r).  Run

sfdisk -uM -l /dev/hda

to get something like:

Disk /dev/hda: 58168 cylinders, 16 heads, 63 sectors/track
Units = megabytes of 1048576 bytes, blocks of 1024 bytes, counting 
from 0

   Device Boot Start   End     MB   #blocks   Id  System
/dev/hda1         0+   750-   751-   768095+  fd  Linux raid 
autodetect
/dev/hda2       750+   908-   159-   162288    5  Extended
/dev/hda3       908+  1108-   201-   205128   fd  Linux raid 
autodetect
/dev/hda4      1108+ 28629- 27521- 28181160   fd  Linux raid 
autodetect
/dev/hda5       750+   780-    31-    30743+  83  Linux
/dev/hda6       780+   908-   129-   131543+  fd  Linux raid 
autodetect

(+ and - after some numbers mean rounding has taken place)


So the Partition_Table info on the OSRCD says:

1st partition (/dev/hda1) = ~750 MB, type 83
Regular Linux partition (/)

2nd partition (/dev/hda2) = ~158 MB, type 5
Extended partition (holds /dev/hda5 and /dev/hda6)

3rd partiton (/dev/hda3) = ~200 MB, type 83
Regular Linux partition (/var)

4th partition (/dev/hda4) = rest of disk, type 83
Regular Linux partition (/home)

5th partition (/dev/hda5) = ~30 MB, type 83

6th partiton (/dev/hda6) = ~ rest of "disk", type 83
(should be about 158-30 or ~128MB)

/dev/hda5 and /dev/hda6 are in the Extended partition (to be honest, 
I'm not sure of their use - fdisk doesn't see them, so I don't think 
they are actually used... probably a remnant from some early disk 
layout that never got removed...)

So to give yourself a 1GB /var and 2GB / (and the rest in /home), 
you'd make your Partition_Table section look like:

# This is the partition table for the product
%begin Partition_Table
0,2000,83
,158,5
,1000,83
,,83
,30,83
,,82
%end Partition_Table

(actual sizes of / and /var might vary a couple of MB depending on 
rounding, etc.)

Then burn your new CD, and your RaQ now has bigger / and /var 
partition!

NOTE: UNOFFICIAL AND UNSUPPORTED. USE AT YOUR OWN RISK.  (Worst case, 
though, is you have to rebuild the disk again with a "real" OSRCD...)

- -- 
Bruce Timberlake

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.1 (GNU/Linux)

iD8DBQE+EedAvLA2hUZ9kgwRAqDEAJ0TttzV/wKcoVMowyP1mkjmTmF+TQCfVJ12
vV+Ik8B5Sq8v548J3z8i9kw=
=x4Fl
-----END PGP SIGNATURE-----