What's The Fuss With Those Tedious Archivers?

[rishi]

I've bee trying to make a backup of my hardisk (Everything minus the partion, where I try to store the archive).

tar goes down after about 30 minutes due to too many errors (mostly because it can't handle the symbolic links, that go by the plenty in linux (at least in suse 10.1).

dar doesn't seem to have problems with those links, but goes down after a couple of hours due to too many reading errors of various kinds.

This all happens on a freshly, default install of suse 10.1 were the install went perfectly without the slightest indication of anything not being perfect. I haven't touched anything, just installed, rebooted a couple of times to make sure things had all settled, opened a session as root and launched the archivers with parameters according to books.

"A couple of hours", I wrote. Under windows I could take a snapshot of my harddisk in 10 minutes, which I could restore in 5 minutes --- and everything would be back to the situation excactly as it were, when I took the snapshot. We're talking about a harddisk-usage about 5 times as big - would probably take the whole day with those archivers, even if it all went smoothless.

Is it impossible to do that basic task under linux with same ease as under windows? If I'm backing up a system that works perfectly to my needs, I really don't care if 0.0001% of the files I'm backing up, should be invalid, corrupted, without proper permission, or whatever.

Edited June 21, 2006 by rishi

[autonomous_unit]

Can you provide some details about what you are doing? Perhaps the output of "df" and the specific tar command you have used (all parameters)? Try not to show us any personal information, but do tell what the drives/partitions are, where they are mounted, what directory you are in when you invoke tar, and what the arguments are. Also include the real error messages...

I have never had problems with tar and symbolic links. Are you accidentally telling tar to also include the directory where the output archive is going? This can lead to amusing but probably unintended results as tar chases its own tail by trying to archive the archive file. Are you forgetting to exclude /proc or /sys? These psuedo-filesystems have rapidly changing files that are invented by the kernel and do not need to be archived. On an inactive system, e.g. one mounted via a rescue system, they are empty directories.

A useful option is --one-filesystem to make sure tar doesn't traverse any mount points. This way, you can make separate archives of each filesystem by starting at its root. I don't know how many filesystems are used with a typical SUSE system, so I am not sure this matters much. Typical example would be to keep separate tar files for / /boot and /home. You can also use the --exclude option to suppress backups where the selection criteria are more complex than a whole filesystem.

Also, you should always be running tar as root to do a system backup, so permissions should not be an issue. When I use tar, it usually goes at the rate I would expect based on the bandwidth of the harddrive(s) in question, considering that it is both reading and writing the archived data... e.g. 25-35 MB/s on my laptop divided between reading and writing, or 100-150 MB/s on a software RAID volume on a server.