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8. Application Specific Notes

I have listed below notes about backing up particular applications.

8.1. Squid

Squid is a http proxy and cache. As such it keeps a lot of temporary data on the hard drive. There is no point in backing that up. Insert "--exclude /var/spool/squid" into the appropriate tar command in your second stage backup script. Then, get squid to rebuild its directory structure for you. Tack onto the tail end of the second stage restore script a command for squid to initialize itself. Here is how I did it over ssh in restore.tester:

ssh $target "mkdir /var/spool/squid ; chown squid:squid /var/spool/squid;\
      /usr/sbin/squid -z;touch /var/spool/squid/.OPB_NOBACKUP"

The last command creates a file of length 0 called .OPB_NOBACKUP. This is for the benefit of Arkeia, and tells Arkeia not to back up below this directory

8.2. Arkeia

These notes are based on testing with Arkeia 4.2.

Arkeia is a backup and restore program that runs on a wide variety of platforms. You can use Arkeia as part of a bare metal restoration scheme, but there are two caveats.

The first is probably the most problematic, as absent any more elegant solution you have to hand select the directories to restore in the navigator at restoration time. The reason is that, apparently, Arkeia has no mechanism for not restoring files already present on the disk, nothing anlogous to tar's -p option. If you simply allow a full restore, the restore will crash as Arkeia over-writes a library which is in use at restore time, e.g. lib/libc-2.1.1.so. Hand selection of directories to restore is at best dicy, so I recommend against it.

The second caveat is that you have to back up the Arkeia data dictionary and/or programs. To do that, modify the save.metatdata script by adding Arkeia to the list of directories to save:

# arkeia specific:
tar cf - usr/knox | gzip -c > $zip/arkeia.tar.gz

You must back up the data dictionary this way because Arkeia does not back up the data dictionary. This is one of my complaints about Arkeia, and I solve it on my own computer by saving the data dictionary to tape with The TOLIS Group's BRU.

The data dictionary will be restored in the script restore.metadata automatically.

8.3. Amanda

Amanda (The Advanced Maryland Automatic Network Disk Archiver) works quite well with this set of scripts. Use the normal Amanda back-up process, and build your first stage data as usual. Amanda stores the data on tape in GNU tar or cpio format, and you can recover from individual files to entire backup images. The nice thing about recovering entire images is that you can then use variants on the scripts in this HOWTO to restore from the images, or direct from tape. I was able to restore my test machine with the directions from W. Curtis Preston's Unix Backup & Recovery. For more information on it, see the Resources. The Amanda chapter from the book is on line.

I made two changes to the script restore.tester. First, I changed it to accept a file name as an argument. Then, since Amanda's amrestore decompresses the data as it restores it, I rewrote it to cat the file into the pipe instead of decompressing it.

The resulting line looks like this:

cat $file | ssh $target "umask 000 ; cd / ; tar -xpkf - "

where $file is the script's argument, the image recovered from the tape by amrestore.

Since the command line arguments to tar prohibit over-writing, restore from images in the reverse of the order in which they were made. Restore most recent first.




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