Mounting a File System on a Partition Inside of an LVM Volume
Tags: fdisk, filesystem, kpartx, kvm, linux, lvm, partition, storage, sysadmin, unix, Virtualization, Xen
In my linux virtual environment I am using LVM volumes as the backing devices for virtual machines. Each of these LVM volumes contains a partition table splitting the LVM volume into at least one linux partition and one swap partition. In order to access these partitions from the dom0 host itself we can use the kpartx command to create device mapper entries which correspond to each of the partitions.
In this example we want to access the ext3 filesystem contained on the first partition of the “vm_example” logical volume.
[root@vm ~]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert vm_example vg0 -wi-ao 6.00G [root@vm ~]# fdisk -l /dev/vg0/vm_example Disk /dev/vg0/vm_example: 6442 MB, 6442450944 bytes 255 heads, 63 sectors/track, 783 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/vg0/vm_example1 1 653 5245191 83 Linux /dev/vg0/vm_example2 654 783 1044225 82 Linux swap / Solaris |
As you can see, partition 1 is type linux and partition 2 is type linux swap. Now we use kpartx with the -a flag to create the device mapper entries for the partitions displayed above.
[root@vm ~]# kpartx -a /dev/vg0/vm_example |
And now we can interact with the /dev/mapper devices as you normally would to mount, fsck, etc.
[root@vm ~]# file -s /dev/mapper/vm_example1 /dev/mapper/vm_example1: Linux rev 1.0 ext3 filesystem data (large files) [root@vm ~]# file -s /dev/mapper/vm_example2 /dev/mapper/vm_example2: Linux/i386 swap file (new style) 1 (4K pages) size 261055 pages |
Then, when you’re finished, clean up with the kpartx -d command. The logical volume will remain in-use until this is done.
[root@vm ~]# kpartx -d /dev/vg0/vm_example |
