Doing it 1999 style: OpenBSD Merging Partitions
This document attempts to outline the steps required to merge multiple partitions back into one.
This is particularly targeting new users to OpenBSD with a few Linuxism’s here and there to make it relatable.
Most of the information in here is already covered on the OpenBSD FAQ. This is not a replacement for it, this document is simply here to walk you though the process with examples so that you can do the same.
The setup
On a VM I configured with 16GB, to run some simple tests, the auto layout created the following partitions
foo# df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/sd0a 404M 84.1M 299M 22% /
/dev/sd0k 2.5G 2.0K 2.4G 0% /home
/dev/sd0d 531M 14.0K 504M 0% /tmp
/dev/sd0f 1.9G 1.2G 666M 64% /usr
/dev/sd0g 525M 298M 200M 60% /usr/X11R6
/dev/sd0h 1.7G 220K 1.6G 0% /usr/local
/dev/sd0j 5.0G 2.0K 4.8G 0% /usr/obj
/dev/sd0i 1.5G 2.0K 1.4G 0% /usr/src
/dev/sd0e 758M 7.5M 712M 1% /var
foo#
Most of the partitions will be fine as is however /usr/src, /usr/obj, will most likely never be used. Moreover, 1.6GB for /usr/local will not be enough to install some eye candy desktop.
The plan (baby steps)
Our plan is to start with something simple at first and with less chances of losing data. We are going to merge /usr/src and /usr/obj into the /usr/local partition.
First we ensure that the partitions are empty as to avoid messing up something and copy whatever is needed back after the merge.
foo# ls -la /usr/src
total 8
drwxrwxr-x 2 root wsrc 512 May 24 03:25 .
drwxr-xr-x 16 root wheel 512 May 24 00:28 ..
foo# ls -la /usr/obj
total 8
drwxrwx--- 2 build wobj 512 May 24 03:25 .
drwxr-xr-x 16 root wheel 512 May 24 00:28 ..
foo#
Both are empty so we proceed into unmounting them
foo# unmount /usr/src
foo# unmount /usr/obj
Temporarily, we unmount the partition for the /usr/local so that we can manipulate it without corruption.
foo# umount /usr/local
If you get an error similar to the following, ensure that you kill any processes that my be using this partition
foo# umount /usr/local
umount: /usr/local: Device busy
Comment out the entries on /etc/fstab to avoid being mounted by accident again and to avoid getting error during our next reboot (since we are going to delete those two).
#9a04e665d7da593d.j /usr/obj ffs rw,nodev,nosuid 1 2
#9a04e665d7da593d.i /usr/src ffs rw,nodev,nosuid 1 2
Let the fun begin
Run the disklabel utility and note the offset and sizes of the partitions
foo# disklabel -E sd0
Label editor (enter '?' for help at any prompt)
sd0>
Display the partition table using human sizes p m and size in blocks with just p
sd0> p m
OpenBSD area: 64-33554432; size: 16384.0M; free: 0.0M
# size offset fstype [fsize bsize cpg]
a: 420.1M 64 4.2BSD 2048 16384 6667 # /
b: 620.2M 860416 swap # none
c: 16384.0M 0 unused
d: 552.1M 2130592 4.2BSD 2048 16384 8764 # /tmp
e: 782.2M 3261376 4.2BSD 2048 16384 12516 # /var
f: 2040.2M 4863424 4.2BSD 2048 16384 12960 # /usr
g: 546.0M 9041728 4.2BSD 2048 16384 8667 # /usr/X11R6
h: 1834.3M 10160032 4.2BSD 2048 16384 12960 # /usr/local
i: 1608.0M 13916640 4.2BSD 2048 16384 12960
j: 5336.1M 17209888 4.2BSD 2048 16384 12960
k: 2644.7M 28138176 4.2BSD 2048 16384 12960 # /home
sd0> p
OpenBSD area: 64-33554432; size: 33554368; free: 16
# size offset fstype [fsize bsize cpg]
a: 860352 64 4.2BSD 2048 16384 6667 # /
b: 1270160 860416 swap # none
c: 33554432 0 unused
d: 1130784 2130592 4.2BSD 2048 16384 8764 # /tmp
e: 1602048 3261376 4.2BSD 2048 16384 12516 # /var
f: 4178304 4863424 4.2BSD 2048 16384 12960 # /usr
g: 1118304 9041728 4.2BSD 2048 16384 8667 # /usr/X11R6
h: 3756608 10160032 4.2BSD 2048 16384 12960 # /usr/local
i: 3293248 13916640 4.2BSD 2048 16384 12960
j: 10928288 17209888 4.2BSD 2048 16384 12960
k: 5416256 28138176 4.2BSD 2048 16384 12960 # /home
The partitions that are of interest to us are i & j. We are going to delete those and merge them into h.
- i offset: 13916640, size: 3293248
- j offset: 10928288, size: 17209888
Note that your values will differ, adapt them accordingly
Delete the two partitions and print the table again to confirm. (NOTE: when you have modifications that are not yet written to disk the * character will be added to the prompt such as sd0*>)
sd0> d i
sd0*> d j
sd0*> p
OpenBSD area: 64-33554432; size: 33554368; free: 14221552
# size offset fstype [fsize bsize cpg]
a: 860352 64 4.2BSD 2048 16384 6667 # /
b: 1270160 860416 swap # none
c: 33554432 0 unused
d: 1130784 2130592 4.2BSD 2048 16384 8764 # /tmp
e: 1602048 3261376 4.2BSD 2048 16384 12516 # /var
f: 4178304 4863424 4.2BSD 2048 16384 12960 # /usr
g: 1118304 9041728 4.2BSD 2048 16384 8667 # /usr/X11R6
h: 3756608 10160032 4.2BSD 2048 16384 12960 # /usr/local
k: 5416256 28138176 4.2BSD 2048 16384 12960 # /home
Lets change our h partition for /usr/local to increase its size. Open a calculator and add up the size values for h,i,j
foo# echo $((3756608+3293248+17209888))
24259744
and add the sum to the size question
sd0*> c h
Partition h is currently 3756608 sectors in size, and can have a maximum
size of 17978144 sectors.
size: [3756608] 24259744
Confirm the new sizes
sd0*> p
OpenBSD area: 64-33554432; size: 33554368; free: 16
# size offset fstype [fsize bsize cpg]
a: 860352 64 4.2BSD 2048 16384 6667 # /
b: 1270160 860416 swap # none
c: 33554432 0 unused
d: 1130784 2130592 4.2BSD 2048 16384 8764 # /tmp
e: 1602048 3261376 4.2BSD 2048 16384 12516 # /var
f: 4178304 4863424 4.2BSD 2048 16384 12960 # /usr
g: 1118304 9041728 4.2BSD 2048 16384 8667 # /usr/X11R6
h: 17978144 10160032 4.2BSD 2048 16384 12960 # /usr/local
k: 5416256 28138176 4.2BSD 2048 16384 12960 # /home
sd0*> p m
OpenBSD area: 64-33554432; size: 16384.0M; free: 0.0M
# size offset fstype [fsize bsize cpg]
a: 420.1M 64 4.2BSD 2048 16384 6667 # /
b: 620.2M 860416 swap # none
c: 16384.0M 0 unused
d: 552.1M 2130592 4.2BSD 2048 16384 8764 # /tmp
e: 782.2M 3261376 4.2BSD 2048 16384 12516 # /var
f: 2040.2M 4863424 4.2BSD 2048 16384 12960 # /usr
g: 546.0M 9041728 4.2BSD 2048 16384 8667 # /usr/X11R6
h: 8778.4M 10160032 4.2BSD 2048 16384 12960 # /usr/local
k: 2644.7M 28138176 4.2BSD 2048 16384 12960 # /home
Great our partition is now ~8GB, lets save and quit the utility (note that q also saves but force of habit dictates saving first before quitting)
sd0*> w
sd0> q
No label changes.
Great from here on you can follow the remaining steps from the OpenBSD FAQ - Grow Partition finish up.
Notice that the FAQ happened to mention the same partition as ours, something tells me this is not by accident
Now lets grow our filesystem to match the new partition definition.
foo# growfs sd0h
We strongly recommend you to make a backup before growing the Filesystem
Did you backup your data (Yes/No) ? Yes
new filesystem size is: 4494536 frags
Warning: 145184 sector(s) cannot be allocated.
growfs: 8707.5MB (17832960 sectors) block size 16384, fragment size 2048
using 43 cylinder groups of 202.50MB, 12960 blks, 25920 inodes.
super-block backups (for fsck -b #) at:
4147360, 4562080, 4976800, 5391520, 5806240, 6220960, 6635680, 7050400, 7465120, 7879840, 8294560, 8709280, 9124000, 9538720, 9953440, 10368160, 10782880, 11197600, 11612320, 12027040, 12441760, 12856480, 13271200, 13685920, 14100640, 14515360,
14930080, 15344800, 15759520, 16174240, 16588960, 17003680, 17418400
Check the filesystem
fsck /dev/sd0h
foo# fsck /dev/sd0h
** /dev/rsd0h
** Last Mounted on /usr/local
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Cyl groups
111 files, 110 used, 4318081 free (57 frags, 539753 blocks, 0.0% fragmentation)
MARK FILE SYSTEM CLEAN? [Fyn?] y
***** FILE SYSTEM WAS MODIFIED *****
Remount your filesystem and check the size
foo# mount /usr/local
foo# df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/sd0a 404M 84.1M 299M 22% /
/dev/sd0k 2.5G 2.0K 2.4G 0% /home
/dev/sd0d 531M 14.0K 504M 0% /tmp
/dev/sd0f 1.9G 1.2G 666M 64% /usr
/dev/sd0g 525M 298M 200M 60% /usr/X11R6
/dev/sd0e 758M 7.6M 712M 1% /var
/dev/sd0h 8.2G 220K 7.8G 0% /usr/local
Congrats you did it… if you liked this guide and want to thank me, please consider supporting the OpenBSD project by making donations or purchases.