How to backup filesystem with tar using a bash script? - bash

Question

I want to backup my ubuntu filesystem, and I wrote this little script. It is very basic, but being my first try I am afraid to do mistakes. And since it will take few hours to complete to see results, I think it is better to ask you as experienced programmers if I did something wrong.
I'm particularly interested in > will that record output of mv or will it output also results of tar?
Also variables inside tar command is it correct way?
#!/bin/bash
mybackupname="backup-fullsys-$(date +%Y-%m-%d).tar.gz"
{ time tar -cfpzv $mybackupname --exclude=/$mybackupname --exclude=/proc --exclude=/lost+found --exclude=/sys --exclude=/mnt --exclude=/media --exclude=/dev / && ls -gh $mybackupname && mv -v $mybackupname backups/filesystem/ ; } > backup-system.log
exit
Anything I should know before I run this?

Answer 1

Sandro, you might want to consider spacing things out in your script and producing individual errors. Makes things much easier to read.
#!/bin/bash
mybackupname="backup-fullsys-$(date +%Y-%m-%d).tar.gz"
# Record start time by epoch second
start=$(date '+%s')
# List of excludes in a bash array, for easier reading.
excludes=(--exclude=/$mybackupname)
excludes+=(--exclude=/proc)
excludes+=(--exclude=/lost+found)
excludes+=(--exclude=/sys)
excludes+=(--exclude=/mnt)
excludes+=(--exclude=/media)
excludes+=(--exclude=/dev)
if ! tar -czf "$mybackupname" "${excludes[#]}" /; then
status="tar failed"
elif ! mv "$mybackupname" backups/filesystem/ ; then
status="mv failed"
else
status="success: size=$(stat -c%s backups/filesystem/$mybackupname) duration=$((`date '+%s'` - $start))"
fi
# Log to system log; handle this using syslog(8).
logger -t backup "$status"
If you wanted to keep debug information (like the stderr of tar or mv), that could be handled with redirection to a tmpfile or debug file. But if the command is being run via cron and has output, cron should send it to you via email. A silent cron job is a successful cron job.
The series of ifs causes each program to be run as long as the previous one was successful. It's like chaining your commands with &&, but lets you run other code in case of failure.
Note that I've changed the order of options for tar, because the thing that comes after -f is the file you're saving things to. Also, the -p option is only useful when extracting files from a tar. Permissions are always saved when you create (-c) a tar.
Others might wish to note that this usage of the stat command works in GNU/Linux, but not other unices like FreeBSD or Mac OSX. In BSD, you'd use stat -f%z $mybackupname.

Answer 2

The file redirection as you have it will only record the output of mv.
You can do
{ tar ... && mv ... ; } > logfile 2>&1
to capture the output of both, plus any errors that may occur.
It's a good idea to always be in the habit of quoting variables when they are expanded.
There's no need for the exit.