I have an existing FreeBSD v4.7 installation and want to delete a small
filesystem that I had designated for email (/var/mail), and want to freeup
that unused space to the '/usr/home' filesystem. If I use DISKLABEL to
delete '/var/mail', and then re-write '/usr/home' to reflect the added
space (writing the changes to the SAME '/usr/home' partition), will that
erase the '/usr/home' filesystem and all of its user-data contents
from the disk itself???
If I understand what you are saying, you have two (ingoring others
that are not involved such as root) file systems /var/mail and /usr/home
and you want to combine the space from /var/mail in to /usr/home.
By filesystems I do not mean just directories within other filesystems.
They are separately mountable entities. If they are just directories
within their respective filesystems eg you have /var and /usr filesystems
and mail is just a directory within /var and home is just a directory
within /usr, then it is a completely different story.
To combine those two filesystems (/var/mail and /usr/home) you need to
repartition the disk using disklabel and then run newfs again. Running
newfs on the newly combined larger partition will wipe out everything
previously (sort of - it doesn't actually overwrite the data, just the
superblocks which makes it unreachable by normal means).
There is something called 'growfs' that can allow a filesystem to grow
to take in some additional free space without wiping out what was already
in the filesystem. I have not yet used growfs, but it might work for you.
I would guess that at the least you would have to use disklabel to remove
the partition that is used for /var/mail.
Someone else might better comment on growfs.
The disk space to be added must be addressibly contiguous to the base
filesystem that you are trying to increase. I believe that is true
for growfs as well as for recreating the filesystem with disklabel and
newfs. If the two spaces are not contiguous, then you will have to
redo your who slice partitioning schema and remake all of the partitions
and re-newfs them.
Since I can't say much about growfs, I will comment only on merging
the full re-creation way. So, presuming the two spaces are contiguous,
NOTE: this is best done in single user mode, but can be done in multi.
make a good backup of the /usr/home filesystem. Use dump(8)
dump -0af /dev/nrsa0 /usr/home (presumes a tape drive. Change the
device to whereever you dump to)
Check it out with restore.
mt rewind
restore -ivf /dev/nrsa0 look around a little, maybe restore a file.
Then unmount the filesystems
umount /usr/home
umount /var/mail
Then bring up disklabel
disklabel -r -e /da0s1 (or whatever the disk slice device is)
edit the partition table to combine the two in to one.
Example, say disklabel shows something like the following:
8 partitions:
#size offset fstype [fsize bsize bps/cpg]
a: 25149440 4.2BSD 2048 1638489 # (Cyl.0 - 156*)
b: 4618240 2514944 swap # (Cyl. 156*- 444*)
c: 355517820 unused 0 0# (Cyl.0 - 2212*)
e: 2514944 7133184 4.2BSD 2048 1638489 # (Cyl. 444*- 600*)
f: 25903654 9648128 4.2BSD 2048 1638489 # (Cyl. 600*- 2212*)
and you want to combine partitions e and f
Edit it to look like the following
(all the stuff after the # is ignored so nuke it)
8 partitions:
#size offset fstype [fsize bsize bps/cpg]
a: 25149440 4.2BSD 2048 1638489 # (Cyl.0 - 156*)
b: 4618240 2514944 swap # (Cyl. 156*- 444*)
c: 355517820 unused 0 0# (Cyl.0 - 2212*)
e: 28418598 7133184 4.2BSD 2048 16384#
Or better yet, if you are using a recent FreeBSD version
8 partitions:
#size offset fstype [fsize bsize bps/cpg]
a: 25149440 4.2BSD 2048 1638489 # (Cyl.0 - 156*)
b: 4618240* swap # (Cyl. 156*- 444*)
c:*0 unused 0 0# (Cyl.0 - 2212*)
e:** 4.2BSD 2048 16384#
The newer disklabel will calculate for you all of the offsets and the
size of the 'c' partition and the last partition if that is to be all
of the remaining disk.
Note in either case you are leaving the other partitons as is (whatever
that may be in your case).
Get out of the editor with a write back (save). You might want to
check it to make sure it is happy by doing:
disklabel -r da0s1 which forces it to read the actual label
Then do the newfs
newfs /dev/rda0s1e Get the device right or you have big trouble
mount the newly remade filesystem
mount /usr/home (presuming it is already in /etc/fstab
