Resizing an LVM partition

[jvincent08]

Alright, I've been googling all day on how to do this. All I wanted to do is shrink an LVM logical volume to free up some space. I've discovered that I need to first shrink the partition that is on the volume, so as not to lose data. The logical volume is spread across 2 320GB hard drives. Here's some info:


root@ubuntu:~# fdisk -l

Disk /dev/sda: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000d87b1

Device Boot Start End Blocks Id System
/dev/sda1 * 1 38913 312568641 f W95 Ext'd (LBA)
/dev/sda5 1 38913 312568609+ 8e Linux LVM

Disk /dev/sdb: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000425a0

Device Boot Start End Blocks Id System
/dev/sdb1 * 1 31 248976 83 Linux
/dev/sdb2 32 274 1951897+ 82 Linux swap / Solaris
/dev/sdb3 275 38913 310367767+ 5 Extended
/dev/sdb5 275 38913 310367736 8e Linux LVM

root@ubuntu:~# lvdisplay
/proc/misc: No entry for device-mapper found
Is device-mapper driver missing from kernel?
Failure to communicate with kernel device-mapper driver.
/proc/misc: No entry for device-mapper found
Is device-mapper driver missing from kernel?
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.20 (2007-06-15)(compat) and kernel driver
--- Logical volume ---
LV Name /dev/VolGroup/Root
VG Name VolGroup
LV UUID YC6zl7-Wp92-U3s6-5fSE-6cbi-glYB-5qkLxe
LV Write Access read/write
LV Status NOT available
LV Size 30.00 GB
Current LE 7680
Segments 1
Allocation inherit
Read ahead sectors 0

--- Logical volume ---
LV Name /dev/VolGroup/Home
VG Name VolGroup
LV UUID etLIAF-eok9-x4P6-5Rgp-X96r-qv8q-y59PLL
LV Write Access read/write
LV Status NOT available
LV Size 564.07 GB
Current LE 144403
Segments 2
Allocation inherit
Read ahead sectors 0
root@ubuntu:~# pvdisplay
--- Physical volume ---
PV Name /dev/sda5
VG Name VolGroup
PV Size 298.09 GB / not usable 2.78 MB
Allocatable yes (but full)
PE Size (KByte) 4096
Total PE 76310
Free PE 0
Allocated PE 76310
PV UUID HaIApD-ZnpM-hn30-5DWn-898Z-DOoQ-PM8oO4

--- Physical volume ---
PV Name /dev/sdb5
VG Name VolGroup
PV Size 295.99 GB / not usable 1.49 MB
Allocatable yes (but full)
PE Size (KByte) 4096
Total PE 75773
Free PE 0
Allocated PE 75773
PV UUID tlzmO7-As83-jZzD-V4Mq-W7V8-2x9y-AilNGh


I tried shrinking the filesystem like so:


root@ubuntu:~# ext2resize /dev/sda1 300112m
ext2resize v1.1.19 - 2001/03/18 for EXT2FS 0.5b
error: End of Device: read 0 of 1024 bytes at 1024
root@ubuntu:~#


And similarly:

root@ubuntu:~# resize2fs /dev/sda1 300112m
resize2fs 1.40.8 (13-Mar-2008)
resize2fs: Attempt to read block from filesystem resulted in short read while trying to open /dev/sda1
Couldn't find valid filesystem superblock.
root@ubuntu:~#


I'm doing this all from the Desktop live cd, so none of the volumes/partitions are mounted. I'm new to LVM, and it sounds promising (supposedly being able to easily resize partitions without losing data), so any help on this will be greatly appreciated. Like I said before, I've been searching on how to do this for a while now. Thanks in advance.

[rowdog]

Well, the first problem is that you're trying to resize an extended partion rather than the actual ext3 filesystem. I believe you need to get lvm and the device mapper running before you can resize a filesystem that's split across 2 disks.

PLEASE BE CAREFUL, DO NOT JUST COPY AND PASTE!!!

I'm no expert in LVM2 but here's what I'd try to do...


boot live cd and get a root shell
install lvm2 in the running system ... aptitude install lvm2
load the kernel module(s?) ... something like modprobe dm_mod
get an idea of the size of the fs you want to resize
mount /dev/VolGroup/Whatever /mnt
df -h /mnt
umount /mnt
now, especially for ext3 you'll want some extra space because you need to store the journal. I usually add about 10G of safety margin.

check the filesystem ... e2fsck -f /dev/VolGroup/Whatever

now, you'll need to know the new size of the fs. Say that df -h said it was 120G, A lot of web sites say how to get the numbers right but I don't want to screw up my filesystems so I would then go with like 130G

resize2fs /dev/VolGroup/Whatever 130G

It's probably not necessary but I always run e2fsck again after resizing.

Now you can lvreduce the logical volume and then maybe even pvresize the physical volume if you want to take the space outside of lvm.

Good Luck!