Evil Home Stereo

I guess this is old news to most people, but I’m still excited: The combination of LVM and ext3 makes it possible to resize a partition while it is still mounted.

The short story:
root@TreeHouse:~# lvextend -L+1G /dev/hd/kubuntu
Extending logical volume kubuntu to 6.00 GB
Logical volume kubuntu successfully resized
root@TreeHouse:~# resize2fs /dev/hd/kubuntu
resize2fs 1.40.8 (13-Mar-2008)
Filesystem at /dev/hd/kubuntu is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/hd/kubuntu to 1572864 (4k) blocks.
The filesystem on /dev/hd/kubuntu is now 1572864 blocks long.
That took maybe two seconds.

The long story: Some time ago I replaced the harddisk in my notebook with a 120 GB one. When I reinstalled Kubuntu, I decided to go with LVM for everything. My typical partitioning scheme has one partition (or volume) for the root, a big one for /home and a separate relatively small one for /var (so eg. /var/tmp can’t fill up your root). Plus a big swap partiton and /tmp mounted as tmpfs (so /tmp can’t fill up root neither). Additionally I usually symlink /usr/src to /var/src. Only /boot is not located in the LVM. Which results in the following fstab:

/dev/hd/kubuntu / ext3 defaults,noatime,errors=remount-ro 0 1
/dev/hd/kubuntu+var /var ext3 defaults,relatime 0 2
/dev/hd/home /home ext3 defaults,relatime 0 3
/dev/hd/media /media/Media ext3 defaults,noatime 0 0
/media/Media/music /home/mss/Music none bind 0 0
/media/Media/pictures /home/mss/Pictures none bind 0 0
/dev/sda1 /boot ext3 defaults,noatime 0 2
/dev/hd/swap none swap sw 0 0
proc /proc proc defaults 0 0
tmp /tmp tmpfs size=3G,mode=1777 0 0

For a typical desktop system partitioned like that and running KDE you don’t need more than 4 GiB for the root.

My initial volumes looked like this:
root@TreeHouse:~# pvdisplay /dev/sda3
--- Physical volume ---
PV Name               /dev/sda3
VG Name               hd
PV Size               110.69 GB / not usable 1.24 MB
Allocatable           yes
PE Size (KByte)       4096
Total PE              28337
Free PE               5809
Allocated PE          22528
PV UUID               3aP8yu-j0R1-gnKW-DXOd-rPjd-BHXz-8gjmP7
root@TreeHouse:~# vgdisplay hd
--- Volume group ---
VG Name               hd
System ID
Format                lvm2
Metadata Areas        1
Metadata Sequence No  20
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                5
Open LV               5
Max PV                0
Cur PV                1
Act PV                1
VG Size               110.69 GB
PE Size               4.00 MB
Total PE              28337
Alloc PE / Size       22528 / 88.00 GB
Free  PE / Size       5809 / 22.69 GB
VG UUID               FBM2Pd-5yTa-iQIE-cJzO-2ZW1-bf2j-CrYymN
root@TreeHouse:~# lvdisplay hd
--- Logical volume ---
LV Name                /dev/hd/home
VG Name                hd
LV UUID                ooX4NK-rScI-0ByG-tBmd-PALp-Y58V-iGCJuy
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                50.00 GB
Current LE             12800
Segments               1
Allocation             inherit
Read ahead sectors     0
Block device           254:0
--- Logical volume ---
LV Name                /dev/hd/kubuntu+var
VG Name                hd
LV UUID                Dg8Dfj-JWTY-6jlj-uER8-u311-5BQp-qTlRju
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                4.00 GB
Current LE             1024
Segments               1
Allocation             inherit
Read ahead sectors     0
Block device           254:1
--- Logical volume ---
LV Name                /dev/hd/kubuntu
VG Name                hd
LV UUID                P3Hf92-Fg2F-JX0Z-Oa2j-nffR-gQrn-dXUYQN
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                5.00 GB
Current LE             1280
Segments               1
Allocation             inherit
Read ahead sectors     0
Block device           254:2
--- Logical volume ---
LV Name                /dev/hd/swap
VG Name                hd
LV UUID                jHyLo5-AEdF-kESY-zKkS-BnbI-NRnZ-EUvwry
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                4.00 GB
Current LE             1024
Segments               1
Allocation             contiguous
Read ahead sectors     0
Block device           254:3
--- Logical volume ---
LV Name                /dev/hd/media
VG Name                hd
LV UUID                aosr8H-zDav-aKhx-zlmx-BUc3-LWnW-glDMw0
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                25.00 GB
Current LE             6400
Segments               1
Allocation             inherit
Read ahead sectors     0
Block device           254:4
As you can see I kept ca. 20 GiB spare space (who needs 100+ GiB anyway…) which I didn’t allocate to any volume.

That saved my ass when yesterday suddenly my updates started to fail (after I installed Lazarus). With all those installed libraries, headers and development environments my system doesn’t really qualify as a standard desktop anymore. Now I can even think about installing the KDE 4.1 Beta packages

In case of less anticipatory planning, you might be interested in another article which explains how you shrink one of your volumes first.