Ask the Expert

Is there a product that will simplify backup for Linux disaster recovery?

Just recently we've started testing the waters of Linux (Red Hat) and everything seems to be going flawlessly except in the area of disaster recovery.

I've been working on Unix systems for about seven years now and I've never actually had to restore a boot drive. So I'd like you to shed some light on this process for me.

In the Windows world we have utilities such as Disk Keeper and Norton to image a disk and bang, disaster-recovery issues solved.

In the Linux world I've tried using Disk Keeper 7.0 for this, but they do not seem to support EXT3 file systems.

I ignored the error messages when creating the drive image, then before I made the restore I actually had to install a basic install of Linux to set up the MBR on the disk. (Apparently this can be avoided by running 'pqdi /MBR') After the image was restored I had to recreate the swap file with 'mkswap -v1 /dev/'

It worked, but was messy. Is there any product out there that I can just pop a disk in, make an image, and restore the image to a new drive without all the hoops?
When

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a file is written to disk, it can't always be written in consecutive blocks. A file that is not stored in consecutive blocks is fragmented. Since the disk's read-write head will have to move more, it takes longer to read a fragmented file. It is desirable to avoid fragmentation, although it is less of a problem in a system with a good buffer cache with read-ahead.

The ext2 file system attempts to keep fragmentation at a minimum by keeping all blocks in a file close together, even if they can't be stored in consecutive sectors. Ext2 effectively allocates the free block that is nearest to other blocks in a file. For ext2, it is seldom necessary to worry about fragmentation. Most distributions come with defragmentation programs. If yours doesn't, follow the link to download defrag.

There are many Windows defragmentations such as Disk Keeper that move blocks around in the file system to remove fragmentation. For other file systems, defragmentation must be done by backing up the file system, re-creating it, and restoring the files from backups. Backing up a file system before defragmenting is a good idea for all file systems, since many things can go wrong during the defragmentation. debugfs is a file system debugger that allows direct access to the file system data structures stored on disk. It can be used to repair a disk that is so broken that fsck can't fix it automatically. It has also been known to be used to recover deleted files. However, debugfs very much requires that you understand what you're doing; a failure to understand can destroy all your data.

No, there is no other product, however products like Acronis and Boot Magic will allow you to resize a swap file.

This was first published in August 2003

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