2

In AIX systems there are the command backup and its counterpart restore meant to make and restore backups, respectively.

But what are the advantages of using them instead of a well-known tar command which would allow us to restore the backed up data in any other system?

EDIT: Documentation for commands: backup and restore

5
  • I thought it was dump that produced backups that restore restored. But then again, I don't know AIX. Did you read the manual for backup/dump? dump can do incremental backups. Also tar is for creating archives, and is not really designed specifically for backups in the same way as other types of more modern software, such as borgbackup and restic.
    – Kusalananda
    Commented Oct 23, 2018 at 15:18
  • @Kusalananda: Yes, I read them. But besides some difference the way the tape device are managed (like ways to add more backups to the same tape), there is no clue about any advantages over tar command, like performance, integrity, ...
    – Luciano
    Commented Oct 23, 2018 at 15:23
  • Since dump is a standard ELF tool introduced with SVr4, the backup program dump has been renamed to ufsdump on Solaris. Maybe a similar rename has been applied to AIX for the same reason.
    – schily
    Commented Oct 23, 2018 at 15:35
  • @Kusalananda: GNU tar claims to support incremental backups and star includes working support for incremental backups. And BTW: this is not against you, but the downvoting trolls are awake now...
    – schily
    Commented Oct 23, 2018 at 15:53
  • Have you ever been interested in an answer on your question, or why is there no reaction on my answer?
    – schily
    Commented Oct 31, 2018 at 10:48

2 Answers 2

0

Lately, the main advantage I got from backup command suit (backup, restore and backsnap) is that they work over JFS2 snapshots. Other commands like tar, cpio and some others cannot, they just fail with some weird or non-descriptive errors, like tar that fail with a blank error:

$ cd /home/myjfshome/.snapshot/snapshot_1
$ tar -cvf /tmp/mytarfile myfile
tar:
-3

The programs dump (backup) and restore are from BSD from around 1980. They implement a working and rock solid incremental backup system.

A normal tar implementation like the tar that is delivered with AIX, is not comparable to a backup system as normal tar implementations do not keep all needed file meta data.

If you however are using star (I am the author of star which is the oldest free tar implementation) to backup a filesystem, you get the same basic algorithm as used by these programs, but the backup is done in a filesystem and OS independent way. Star also gives you a rock solid incremental backup system.

See http://schilytools.sourceforge.net/man/man1/star.1.html for more information.

Since star is able to use any size of FIFO (e.g. several gigabytes if you specify a related fs= option) and the BSD backup program only supports a small number of 63 kBytes buffer, star is faster than the historic method. This is important if you like to backup directly to a tape device that needs to be be kept in streaming mode.

Note: there is currently not yet support for NFSv4 ACLs on AIX in star, I cannot speak for the state for the withdrawn POSIX draft ACLs on AIX as I currently have no access to an AIX machine.

Another popular program seems to be gnu tar, but this program has no ACL support and it claims to support incremental backups and restores, but fails to restore an incremental if there are non-trivial changes in the filesystem between two incremental backups.

See this Is it possible to use tar for full system backups? for a script to repeat the well known GNU tar bug (present since 1992 and reported several time since 2004).

Here is an in dept comparison: linux tar listed-incremental untrustworthy

3
  • Thanks by the additional infos you gave here, but I really need to know the differences between backup and tar commands in AIX.
    – Luciano
    Commented Oct 31, 2018 at 11:10
  • OK, I added a small paragraph for typical tar implementations delivered with UNIX installations. Does this help? If you like to know more, you would need to give explicit questions.
    – schily
    Commented Oct 31, 2018 at 11:18
  • BTW: I forgot to hit the "save" button after editing the answer, so the content was not visible 12 minutes after i send the comment
    – schily
    Commented Oct 31, 2018 at 12:54

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .