Topics: AIX, Backup & restore, LVM, System Admin

Use dd to backup raw partition

The savevg command can be used to backup user volume groups. All logical volume information is archived, as well as JFS and JFS2 mounted filesystems. However, this command cannot be used to backup raw logical volumes.

Save the contents of a raw logical volume onto a file using:

# dd if=/dev/lvname of=/file/system/lvname.dd
This will create a copy of logical volume "lvname" to a file "lvname.dd" in file system /file/system. Make sure that wherever you write your output file to (in the example above to /file/system) has enough disk space available to hold a full copy of the logical volume. If the logical volume is 100 GB, you'll need 100 GB of file system space for the copy.

If you want to test how this works, you can create a logical volume with a file system on top of it, and create some files in that file system. Then unmount he filesystem, and use dd to copy the logical volume as described above.

Then, throw away the file system using "rmfs -r", and after that has been completed, recreate the logical volume and the file system. If you now mount the file system, you will see, that it is empty. Unmount the file system, and use the following dd command to restore your backup copy:
# dd if=/file/system/lvname.dd of=/dev/lvname
Then, mount the file system again, and you will see that the contents of the file system (the files you've placed in it) are back.



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