Logical Volume Manager
- 1 Overview
- 2 Installation
- 3 Create the LVM Partition
- 4 Set up the Logical Volume Structure
- 5 Create the file systems
- 6 Mounting home and srv
- 7 Set them to mount automatically
- 8 Test it
Logical Volume Management provides a lot of flexibility in managing the file system. Partitions can be resized at any time. There's also a snapshot feature.
Here's a simple overview, based on the diagram in http://tldp.org/HOWTO/LVM-HOWTO/ (originally supplied by Erik Bågfors on the linux-lvm mailing list).
ext2 xfs xfs Filesystems | | | usrlv varlv rootlv Logical Volumes (LVs) \ | / \ | / diskvg Volume Group (VG) / \ / \ sdb1 sdc1 Physical Volumes (PVs) on partitions or whole disks
- File systems sit on top of Logical Volumes (LVs) or "abstract partitions".
- LVs are carved out of Volume Groups, an abstraction used to organize a set of Physical Volumes (PVs).
- PVs are typically disks, or disk-like things (e.g. a Software RAID).
The setup will touch on all four of the levels in this diagram.
Install the LVM package
$ sudo apt-get install lvm2
Create the LVM Partition
Make it the size of the entire second drive. Check with
The list will include the 2 disks, one (usually sda1) holding the system and the other (usually sdb1), depending on what it had on it, other stuff.
Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 73917408 1016796 69145824 2% / varrun 517704 760 516944 1% /var/run varlock 517704 4 517700 1% /var/lock udev 517704 76 517628 1% /dev devshm 517704 0 517704 0% /dev/shm /dev/sdb1 other stuff...
$ sudo fdisk /dev/sdb
Use p to see the current partitions.
Command (m for help): p
Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x3eef1cc1 Device Boot Start End Blocks Id System /dev/sdb1 1 60801 488384001 8e Linux swap / Solaris
Create a new LVM partition that spans the whole disk.
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-621, default 1):<ENTER> Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-60801, default 60801): <ENTER> Or the max number if it's not the default
Assign the partition type as LVM.
Command (m for help): t Partition number (1-4): 1 Hex code (type L to list codes): 8E The code for LVM is 8E Changed system type of partition 1 to 8E (Linux LVM)
Use p again to see the new partition.
Command (m for help): p Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x3eef1cc1 Device Boot Start End Blocks Id System /dev/sdb1 1 60801 488384001 8e Linux LVM
Write the new partition table.
Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
Check that it worked.
$ sudo sfdisk -l /dev/sdb
Disk /dev/sdb: 60801 cylinders, 255 heads, 63 sectors/track Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0 Device Boot Start End #cyls #blocks Id System /dev/sdb1 0+ 60800 60801- 488384001 8e Linux LVM /dev/sdb2 0 - 0 0 0 Empty /dev/sdb3 0 - 0 0 0 Empty /dev/sdb4 0 - 0 0 0 Empty
A partitioning howto with more detail is at: http://tldp.org/HOWTO/Partition/
Set up the Logical Volume Structure
I wanted to set up a single volume group for the entire 500G logical volume partition, called "system". From that, I wanted to allocate 150G as a 50G logical volume for /home and a 100G logical volume for a samba partition, /srv.
Create the Physical Volume (PV)
$ sudo pvcreate /dev/sdb1 Physical volume "/dev/sdb1" successfully created
Check if it's there.
$ sudo pvs PV VG Fmt Attr PSize PFree /dev/sdb1 system lvm2 a- 465.76G 465.76G
Create the Volume Group (VG)
I named my group "system".
$ sudo vgcreate system /dev/sdb1
Check if it's there.
$ sudo vgs VG #PV #LV #SN Attr VSize VFree system 1 2 0 wz--n- 465.76G 465.76G
Create the LVM Partitions
Since these are going to be mounted as /home and /srv, use those names.
The first time I tried this, I got an error. A little newsgroup searching found a bug report. Before the first time you use lvcreate, you need to issue
$ sudo modprobe dm_mod
Then proceed with the volume creation.
$ sudo lvcreate --size 50G --name home $ sudo lvcreate --size 100G --name srv
Check that they are there.
$ sudo lvs LV VG Attr LSize Origin Snap% Move Log Copy% home system -wi-ao 50.00G srv system -wi-ao 100.00G
More detail on LVM is at http://tldp.org/HOWTO/LVM-HOWTO/
Create the file systems
Create a file system on each logical volume
I chose ext3 as the file type. There are other choices, but this one is well supported, tired and true. There's a good discussion of the consideration in "Beginning Ubuntu Server Administration", by Sander van Vugt, ISBN 978-1-59059-923-5.
The logical volumes are in /dev/mapper and named using the pattern <lvgroup>-<lvname>. The home logical volume is at /dev/mapper/system-home.
Use mkfs to create the file systems.
$ mkfs.ext3 /dev/mapper/system-home
mke2fs 1.27 (30-Jun-2005) Filesystem label= OS type: Linux ... Writing inode tables: done Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 35 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.
Repeat for the second LV.
$ mkfs.ext3 /dev/mapper/system-srv
The filesysestem is complete, and ready to use. It only needs to be mounted.
Mounting home and srv
The srv volume is easy since it exists as an empty directory.
$ sudo mount -t ext3 /dev/mapper/system-srv /srv
If it doesn't, create it:
$ sudo mkdir /srv
This is slightly more complicated for /home because I already have it mounted and it has a few files in it. There's a tutorial on moving your home directory that covers the issue of file copying at: http://ubuntu.wordpress.com/2006/01/29/move-home-to-its-own-partition/
Make a temporary directory to copy the old /home files into.
$ sudo mkdir /mnt/newhome
$ sudo mount -t ext3 /dev/mapper/system-home /mnt/newhome
Copy the files from the old home directory into it. Then unmount it and move the original home out of the way.
$ sudo umount /mnt/newhome $ sudo mv /home /oldhome
Create a new /home directory and mount it to the system-home logical volume.
$ sudo mkdir /home $ sudo mount -t ext3 /dev/mapper/system-home /home
All of the files should be there. Clean up:
$ sudo remdir /mnt/newhome $ sudo remdir /oldhome
Set them to mount automatically
Use your favorite editor and add the following lines to /etc/fstab
/dev/mapper/system-home /home ext3 defaults 0 0 /dev/mapper/system-srv /srv ext3 defaults 0 0
Reboot and check to see if the mounts came back. (By this time, I'd added a few more files to /srv.)
Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 73917408 1016776 69145844 2% / varrun 517704 760 516944 1% /var/run varlock 517704 4 517700 1% /var/lock udev 517704 76 517628 1% /dev devshm 517704 0 517704 0% /dev/shm /dev/mapper/system-home 51606140 184316 48800384 1% /home /dev/mapper/system-srv 103212320 5512444 92456996 6% /srv