11.9. Extending a logical volume
To extend a logical volume you simply tell the lvextend command how
much you want to increase the size. You can specify how much to
grow the volume, or how large you want it to grow to:
# lvextend -L12G /dev/myvg/homevol
lvextend -- extending logical volume "/dev/myvg/homevol" to 12 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended
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will extend /dev/myvg/homevol to 12 Gigabytes.
# lvextend -L+1G /dev/myvg/homevol
lvextend -- extending logical volume "/dev/myvg/homevol" to 13 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended
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will add another gigabyte to /dev/myvg/homevol.
After you have extended the logical volume it is necessary to
increase the file system size to match. how you do this depends on
the file system you are using.
By default, most file system resizing tools will increase the size
of the file system to be the size of the underlying logical volume
so you don't need to worry about specifying the same size for each
of the two commands.
ext2/ext3
Unless you have patched your kernel with the ext2online
patch it is necessary to unmount the file system before
resizing it. (It seems that the online resizing patch is
rather dangerous, so use at your own risk)
# umount /dev/myvg/homevol/dev/myvg/homevol
# resize2fs /dev/myvg/homevol
# mount /dev/myvg/homevol /home
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If you don't have e2fsprogs 1.19 or later, you can download
the ext2resize command from
ext2resize.sourceforge.net
and use that:
# umount /dev/myvg/homevol/dev/myvg/homevol
# ext2resize /dev/myvg/homevol
# mount /dev/myvg/homevol /home
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For ext2 there is an easier way. LVM 1 ships with a utility
called e2fsadm which does the lvextend and resize2fs for you
(it can also do file system shrinking, see the next section).
 | LVM 2 Caveat |
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There is currently no e2fsadm equivalent for
LVM 2 and the e2fsadm that ships with LVM 1
does not work with LVM 2.
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# e2fsadm -L+1G /dev/myvg/homevol
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is equivalent to the two commands:
# lvextend -L+1G /dev/myvg/homevol
# resize2fs /dev/myvg/homevol
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 | Note |
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You will still need to unmount the file system before
running e2fsadm.
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reiserfs
Reiserfs file systems can be resized when mounted or
unmounted as you prefer:
Online:
# resize_reiserfs -f /dev/myvg/homevol
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Offline:
# umount /dev/myvg/homevol
# resize_reiserfs /dev/myvg/homevol
# mount -treiserfs /dev/myvg/homevol /home
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xfs
XFS file systems must be mounted to be resized and the
mount-point is specified rather than the device name.
jfs
Just like XFS the JFS file system must be mounted to be
resized and the mount-point is specified rather than the
device name. You need at least Version 1.0.21 of the
jfs-utils to do this.
# mount -o remount,resize /home
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| Known Kernel Bug |
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Some kernel versions have problems with this syntax
(2.6.0 is known to have this problem). In this case you
have to explicitly specify the new size of the
filesystem in blocks. This is extremely error prone as
you must know the blocksize of your
filesystem and calculate the new size based on those
units.
Example: If you were to resize a JFS file system to 4
gigabytes that has 4k blocks, you would write:
# mount -o remount,resize=1048576 /home
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