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Linux Administrator's Security Guide
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Linux Backup Guide

By Kurt Seifried kurt@seifried.org

I don't know how many times I can tell people, but it never ceases to amaze me how often people are surprised by the fact that if they do not backup their data it will be gone, if the drive suffers a head crash on them or they hit 'delete' without thinking. Always backup your system, even if it's just the config files, you'll save yourself time and money in the long run. This is even on the SANS top 20 list.

To backup your data under Linux there are many solutions, all with various pro's and con's. There are also several industrial strength backup programs, the better ones support network backups which are a definite plus in a large non-homogenous environment.

One of the other critical things to remember with backups is that whoever has access to them (backup admin, cleaning staff) will have access to all your files unless you encrypt the backups. Physically securing backups is critical, damaging backups physically so they cannot be recovered is extremely easy, with magnetic media simply place a strong magnet near them, for CD's simply scratching the surface or cracking the CD will prevent usage. You should also keep a relatively recent set of backups offsite in case the building burns down or is inaccessible for some other reason (such as a chemical spill).

Contents

Non-commercial backup programs for Linux

There are numerous non commercial backup programs for Linux ranging from simple tools suitable for saving a few files to professional multi-system network backups.

Tar and Gzip or Bzip2

Oldies but still goldies, tar and gzip. Why? Because like vi you can darn near bet the farm on the fact that any UNIX system will have tar and gzip. They may be slow, klunky and starting to show their age, but it's a universal tool that will get the job done. I find with Linux the installation of a typical system takes 15-30 minutes depending on the speed of the network/cdrom, configuration another 5-15 (assuming I have backups or it is very simple) and data restoration takes as long as it takes (definitely not something you should rush). Good example: I recently backed up a server and then proceeded to blow the filesystem away (and remove 2 physical HD's that I no longer needed), I then installed Red Hat 5.2, and reconfigured all 3 network cards, Apache (for about 10 virtual sites), Bind and several other services in about 15 minutes. If I had done it from scratch it would have taken me several hours. Simply:

tar -cvf archive-name.tar dir1 dir2 dir3....

to create the tarball of all your favorite files (typically /etc, /var/spool/mail/, /var/log/, /home, and any other user/system data), followed by a:
gzip -9 archive-name.tar
to compress it as much as possible (granted harddrive space is cheaper then a politicians promise but compressing it makes it easier to move around). You might want to use bzip2, which is quite a bit better then gzip at compressing text, but it is quite a bit slower. I typically then make a copy of the archive on a remote server, either by ftping it or emailing it as an attachment if it's not too big (e.g. the backup of a typical firewall is around 100k or so of config files).

rsync

rsync is an ideal way to move data between servers. It is very efficient for maintaining large directory trees in synch (not real time mind you), and is relatively easy to configure and secure. rsync does not encrypt the data however so you should use something like SSH or IPSec if the data is sensitive (SSH is easiest, simply use "-e ssh").

Amanda

Amanda is a client/server based network backup programs with support for most unices and Windows (via SAMBA). Amanda is BSD style licensed and available from: http://www.amanda.org/. Amanda now ships standard with a number of distributions.

Commercial backup programs for Linux

BRU

BRU (Backup and Restore Utility), has been in the Linux world since as long as Linux Journal (they have had ads in there since the beginning as far as I can tell). This program affords a relatively complete set of tools in a nice unified format, with command line and a graphical front end (easy to automate in other words). It supports full, incremental and differential backups, as well as catalogs, and can write to a file or tape drive, basically a solid, simple, easy to use backup program. BRU is available at http://www.tolisgroup.com/products3.html.

Quickstart

Quickstart is more aimed at making an image of the system so that when the hard drive fails/etc. you can quickly re-image a blank disk and have a working system. It can also be used to 'master' a system and then load other systems quickly (as an alternative to say Red Hat's KickStart). It's reasonably priced as well and garnered a good revue in Linux Journal (Nov 1998, page 50). You can get it at: http://www.tolisgroup.com/products3.html.


Backup Professional

http://www.unitrends.com/br_bp.html

CTAR

http://www.unitrends.com/ctar.html

CTAR:NET

http://www.unitrends.com/br_ct.html

PC ParaChute

http://www.unitrends.com/ps_cr.html

Legato Networker

Legato Networker is another enterprise class backup program, now completely supported on Linux as both client and server. You can get it from: http://www.legato.com/.

Backup media

There are more things to back data up onto than you can drive a range rover over but here are some of the more popular/sane alternatives:

Name of Media Pro's Con's
Hard Drive It's fast. It's cheap. It's huge (160 gigs). It's pretty reliable. ($2-$3 USD per gig) It might not be big enough, and they do fail, usually at the worst possible time. Harder to take offsite as well. RAID is a viable option though.
CDROM Not susceptible to EMP, and everyone in the developed world has a CDROM drive. Media is also pretty sturdy and cheap ($0.20 USD per 650 Megs or so) CDROM's do have a finite shelf life of 5-15 years, and not all recordables are equal. Keep away from sunlight, and make sure you have a CDROM drive that will read them.
Tape It's reliable, you can buy BIG tapes, tape carousels and tape robots, but they're not very cheap. Magnetic media, finite life span and some tapes can be easily damaged (you get what you pay for), also make sure the tapes can be read on other tape drives (in case the server burns down....).
Floppies I'm not kidding, there are rumors some people still use these to backup data. It's a floppy. They go bad and are very small. Great for config files though.
Zip Disks I have yet to damage one, nor have my cats. They hold 100 megs which is good enough for most single user machines. Not everyone has a zip drive, and they are magnetic media. The IDE and SCSI models are passably fast, but the parallel port models are abysmally slow. Watch out for the click of death.
Jazz Drives 1 or 2 gig removable hard drives, my SCSI one averages 5 meg/sec writes. They die. I'm on my third drive. The platters also have a habit of going south if used heavily. And they aren’t cheap. They are junk.
LS120 120 Megs, and cheap, gaining in popularity (hah, I actually believed that). These things are dead as far as I can tell. Slow. I'm not kidding. 120 megs over a floppy controller to something that is advertised as "up to 3-4 times faster then a floppy drive".
Printer Very long shelf life. requires a standard Mark 1 human being as a reading device. Handy for showing consultants and as reference material. Cannot be easily altered. You want to retype a 4000 entry password file? OCR is another option as well.
Linux Administrator's Security Guide
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  Copyright Kurt Seifried 2001 kurt@seifried.org. Published under the terms of the Open Content License Design by Interspire