How to resize an LVM physical volume without a reboot
Tue, 2009.07.28 - 15:22 — müzso
The essential information -that I lacked- was here: "Avoid Reboot after Partition Change with Fdisk". I've found references to the
Now for a detailed example ...
Let's assume you've an LVM volume group named
Note that this is not for beginners. One small mistake and you can easily lose all your data on the given volume group!
Here're the commands to achieve that pv expansion without a reboot:
/sys/block/sda/device/rescan Sysfs entry too, but it seemed not to help. The partprobe command on the other hand worked like a charm.Now for a detailed example ...
Let's assume you've an LVM volume group named
vol01 that has a physical volume named /dev/sda2. You still have free space on the /dev/sda disk and you'd like to increase the size of the sda2 partition and extend the associated physical volume ... thus increasing the free space in your volume group.Note that this is not for beginners. One small mistake and you can easily lose all your data on the given volume group!
Here're the commands to achieve that pv expansion without a reboot:
# First unmount everything that uses the given volume group
# List all the logical volumes that are in vol01
$ lvdisplay /dev/vol01
--- Logical volume ---
LV Name /dev/vol01/lv01
VG Name vol01
LV UUID q3eQP3-4V9E-7yvo-LUZR-zbXz-F2Mh-Pn5fDt
LV Write Access read/write
LV Status available
# open 1
LV Size 139.70 GB
Current LE 35762
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:0
--- Logical volume ---
LV Name /dev/vol01/lv02
VG Name vol01
LV UUID b53h7W-VO2U-3Ok5-WvW3-GbDp-Tbvb-6bbdkw
LV Write Access read/write
LV Status available
# open 1
LV Size 29.31 GB
Current LE 7504
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:1
# Now unmount all these volumes (if they are mounted)
$ umount /dev/vol01/lv01
$ umount /dev/vol01/lv02
# In case you get a "device is busy" error, check out what processes use them (lsof /dev/vol01/lv01) and stop/kill them.
# Now deactive the volume group.
$ vgchange -a n vol01
# Increase the size of the sda2 partition to the desired value.
# You do this by deleting the partition and recreating it with a higher end cylinder.
# I assume that pvresize can handle partition expansions only if the partition start remains the same and the partition end cylinder is moved to a higher value.
$ fdisk /dev/sda
The number of cylinders for this disk is set to 60801.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): p
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000e4bad
Device Boot Start End Blocks Id System
/dev/sda1 1 486 3903763+ 83 Linux
/dev/sda2 487 18722 146480670 8e Linux LVM
Command (m for help): d
Partition number (1-4): 2
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (487-60801, default 487):
Using default value 487
Last cylinder or +size or +sizeM or +sizeK (487-60801, default 60801):
Using default value 60801
Command (m for help): t
Partition number (1-4): 2
Hex code (type L to list codes): 8e
Changed system type of partition 2 to 8e (Linux LVM)
Command (m for help): p
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000e4bad
Device Boot Start End Blocks Id System
/dev/sda1 1 486 3903763+ 83 Linux
/dev/sda2 487 60801 484480237+ 8e Linux LVM
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
# Now comes the interesting part: we force the system with partprobe to re-read the partition table.
$ pvdisplay /dev/sda2
--- Physical volume ---
PV Name /dev/sda2
VG Name vol01
PV Size 139.69 GB / not usable 3.53 MB
Allocatable yes (but full)
PE Size (KByte) 4096
Total PE 35761
Free PE 0
Allocated PE 35761
PV UUID S0cDcl-7mr8-2AAb-172u-HClq-J2aQ-DfC2V5
$ partprobe
$ pvresize /dev/sda2
$ pvdisplay /dev/sda2
--- Physical volume ---
PV Name /dev/sda2
VG Name vol01
PV Size 462.04 GB / not usable 1.04 MB
Allocatable yes
PE Size (KByte) 4096
Total PE 118281
Free PE 82520
Allocated PE 35761
PV UUID S0cDcl-7mr8-2AAb-172u-HClq-J2aQ-DfC2V5
# Voala! :-) The physical volume got increased.
# Time to reactivate the volume group.
$ vgchange -a y vol01
# Now check the volume group details.
$ vgdisplay vol01
--- Volume group ---
VG Name vol01
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 18
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 3
Open LV 3
Max PV 0
Cur PV 2
Act PV 2
VG Size 927.79 GB
PE Size 4.00 MB
Total PE 237515
Alloc PE / Size 68866 / 269.01 GB
Free PE / Size 168649 / 658.79 GB
VG UUID 0eY2tg-AOny-XsDL-wfLR-d290-2jxO-TDTNnQ
# You can now use lvextend to increase logical volumes in the volume group.
$ lvextend -L +10G --name lv01 /dev/vol01
# And resize2fs to extend the Ext2/3 filesystem on the logical volume.
$ resize2fs /dev/vol01/lv01
# And finally mount the filesystems.
$ mount /dev/vol01/lv01
$ mount /dev/vol01/lv02
# You're now ready.
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Comments
What to do if partprobe also suffers from Device Busy?
Error: Error informing the kernel about modifications to partition /dev/sdb1 -- Device or resource busy. This means Linux won't know about any changes you made to /dev/sdb1 until you reboot -- so you shouldn't mount it or use it in any way before rebooting.
Warning: The kernel was unable to re-read the partition table on /dev/sdb (Device or resource busy). This means Linux won't know anything about the modifications you made until you reboot. You should reboot your computer before doing anything with /dev/sdb.
Re: What to do if partprobe also suffers from Device Busy?
partprobeworks only with a certain kernel version and above. I had the following, when got partprobe working successfully:Linux server44 2.6.26-2-xen-amd64 #1 SMP Thu Aug 20 00:36:34 UTC 2009 x86_64 GNU/LinuxAs this is still up to date
Re: As this is still up to date
fuser -mis an option too. Although I "trust"lsofmore.fdisk-partprobe
Worked like a charm for me. Thanks a lot.
Thx for an excellent howto.
The only info that was missing is that you might have to turn swap off (using swapoff) if you happen to have the swap as a LV. After turning the swap off, inactivate the volume:
lvm lvchange -a n vol01/xyzAt least, I found no way to umount the LV that was used for swap.
I guess the biggest problem was that the swap didn't show up in the df output so I didn't understand why/where the last LV was mounted.
regarding swap-partition ...
shows the device(file)name(s) used for swap and
swapoff /dev/path/to/device
umounts the specific one (if possible / unused)
Thanks for the feedback!
Thank you - very helpful article.
Re: Thank you - very helpful article
Very helpful
I had to boot my system from a rescue CD (RIPLinux) before I could umount my LVM LV, and after extending the LV I had to extend reiserfs file system which requires this command:
resize_reiserfs -f /dev/vol01/lv01
Well...
THANK YOU!
Query about data loss after using the given steps
Re: Query about data loss after using the given steps
Your question already tells me that you're not familiar with how various disk partitioning methods work, so most probably you should not attempt this "surgery". Especially if on a "live" (or production) system. If you choose to give it a try, I strongly suggest you first do a test run. Create a new physical volume, a new volume group and logical volumes in it, format the LVs with a filesystem, put some data on it and go through the steps of this post. If you really want to be on the safe side, you do all this in a virtual machine.
As for your actual question: deleting a partition does not remove the actual data from the physical storage that was in that partition. The whole point of this post is to do a PV extension without loosing any data and without rebooting the server.