Programming Forums - BASH backup script

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- - BASH backup script (http://www.programmingforums.org/showthread.php?t=44594)

carlw

Apr 9th, 2012 3:13 AM

BASH backup script

Hi Guys, I'm working on a backup script for a university project. It needs a lot of work but I'm a BASH beginner.

My issue is: I'm trying to implement a solution where the user can just enter as the first argument, the name of the account to backup and as the second argument, f for a full backup or i for an incremental backup.

My code:

#!/bin/bash

SOURCEDIR="/home/$1"

TARGETDIR="/mnt/backup/"

OUTPUTFILE=$1backup-$(date +%Y%m%d).tar.gz

USERFILE="$1backup-\w+.tar.gz"





function incbackup {

tar -xvfz $TARGETDIR$USERFILE

tar -uvfz $TARGETDIR$USERFILE

}



function fullbackup {

tar -zcvpf $TARGETDIR$OUTPUTFILE $SOURCEDIR

}



if [ $2 = f ]; then

echo "Running Full Backup"

fullbackup

exit

        elif [ $2 = i ]; then

        echo "Running Incremental Backup"

        incbackup

        exit

                else

echo "usage ./backupscript [username] [f for full or i for incremental]"

fi

exit

The full backup works OK I think. The incremental has trouble locating the existing file - I tried to use regex in the variable "$USERFILE" - I gather this won't work?

Also I've been reading through the "man tar". I think my flags are OK?
tar -xvfz $TARGETDIR$USERFILE <- "extract, listing verbosely, the file with zip"
tar -uvfz $TARGETDIR$USERFILE <- "update listing verbosely, the file with zip"

How do my flags look?

Thanks in advance.

watael

Apr 9th, 2012 9:45 AM

Re: BASH backup script

hi,

bash doesn't understand regexes (except inside double square brackets with tilde)
You have to use globs, and extended globs.
Check bash's man page for 'Pathname Expansion'

carlw

Apr 9th, 2012 9:51 AM

Re: BASH backup script

Quote:

Originally Posted by watael (Post 234160)

hi,

bash doesn't understand regexes (except inside double square brackets with tilde)
You have to use globs, and extended globs.
Check bash's man page for 'Pathname Expansion'

Thank you sir! I will read that tonight.

carlw

Apr 9th, 2012 10:13 PM

Re: BASH backup script

OK so after reading: http://wiki.bash-hackers.org/syntax/expansion/globs

I changed my code:

#!/bin/bash

SOURCEDIR="/home/$1"

TARGETDIR="/mnt/backup/"

OUTPUTFILE=$1backup-$(date +%Y%m%d).tar.gz

USERFILE="$1backup-*.tar.gz"





function incbackup {

echo "Extracting Previous Backup"

tar -xvfz $TARGETDIR$USERFILE

echo "Updating Backup File"

tar -uvfz $TARGETDIR$USERFILE

}



function fullbackup {

tar -zcvpf $TARGETDIR$OUTPUTFILE $SOURCEDIR

}



if [ $2 = f ]; then

echo "Running Full Backup"

echo "-------------------"

fullbackup

exit

        elif [ $2 = i ]; then

        echo "Running Incremental Backup"

        echo "--------------------------"

        incbackup

        exit

                else

echo "usage ./backupscript [username] [f for full or i for incremental]"

fi

exit

I had done a full backup on the 8th of April and here's the output when I try to do an incremental today:

carl@ubuntubox:~$ ./backupscript carl i
Running Incremental Backup
--------------------------
Extracting Previous Backup
tar: /mnt/backup/carlbackup-20120408.tar.gz: Not found in archive
tar: Exiting with failure status due to previous errors
Updating Backup File
tar: Removing leading `/' from member names
/mnt/backup/carlbackup-20120408.tar.gz
carl@ubuntubox:~$

Do I need different flags or is it just not possible to use gzip when doing this type of incremental backup?

sharted

Apr 10th, 2012 5:18 AM

Re: BASH backup script

I see several things you might benefit from considering:

1) you never check the return value of tar. You can do this by look at the $? variable;

2) I _think_ this error message might be because you have more than one backup in your /mnt/backup directory. When you pass more arguments to tar's extract capability it tries to extract subsequent files from the archive. I.e. imagine that

/mnt/backup/carlbackup-*.tar.gz

expands to

/mnt/backup/carlbackup-20120407.tar.gz /mnt/backup/carlbackup-20120408.tar.gz

tar will think you want to extract /mnt/backup/carlbackup-20120408.tar.gz from /mnt/backup/carlbackup-20120407.tar.gz. Given that this first file probably doesn't exist in the backup, you'll see the error message you see.

Of course, I could be completely wrong about this.... :) What's in your backup directory?

Have you tried doing what you want to do just at the command line?

hth

carlw

Apr 10th, 2012 5:30 AM

Re: BASH backup script

Nice to hear from you again Sharted!

You're right, it doesn't work on the command line.

carl@ubuntubox:~$ cd /mnt/backup
carl@ubuntubox:/mnt/backup$ ls
backup-20120408.tgz carlbackup-20120408.tar.gz
carl@ubuntubox:/mnt/backup$ tar -xvfz carlbackup-20120408.tar.gz
tar: z: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now
carl@ubuntubox:/mnt/backup$ tar -xvfz /mnt/backup/carlbackup-20120408.tar.gz
tar: z: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now

OH WAIT I JUST FOUND THIS -- http://stackoverflow.com/questions/7...mmand-tar-xvfz
You leave the dash off the flags for some reason.
Also I need sudo - so I'll lookup how to implement sudo in to the script.

carlw

Apr 10th, 2012 5:56 AM

Re: BASH backup script

Here is some strange behaviour:

carl@ubuntubox:/mnt/backup$ ls

carlbackup-20120410.tar.gz

carl@ubuntubox:/mnt/backup$ sudo tar xfz carlbackup-20120410.tar.gz

carl@ubuntubox:/mnt/backup$ ls

carlbackup-20120410.tar.gz  home

carl@ubuntubox:/mnt/backup$ cd home

carl@ubuntubox:/mnt/backup/home$ cd carl

carl@ubuntubox:/mnt/backup/home/carl$ ls

backupscript  etc_passwd.awk  etc_passwd_printnice.sh  home  lovescript.pl  month2.pl  mystudentadd.plx

carl@ubuntubox:/mnt/backup/home/carl$ cd

carl@ubuntubox:~$ ls

backupscript  etc_passwd.awk  etc_passwd_printnice.sh  home  lovescript.pl  month2.pl  mystudentadd.plx  testest  z

carl@ubuntubox:~$ sudo ./backupscript carl i

Running Incremental Backup

--------------------------

Updating Backup File

tar: Removing leading `/' from member names

tar: /home/carl/z: file is the archive; not dumped

carl@ubuntubox:~$

It seems to create a file called "z" in my home. I'm not sure why it's doing that.
The script is:

#!/bin/bash

SOURCEDIR="/home/$1"

TARGETDIR="/mnt/backup/"

OUTPUTFILE=$1backup-$(date +%Y%m%d).tar.gz

USERFILE="$1backup-*.tar.gz"





function incbackup {

echo "Updating Backup File"

tar -ufz $TARGETDIR$USERFILE $SOURCEDIR

}



function fullbackup {

tar -cpfz $TARGETDIR$OUTPUTFILE $SOURCEDIR

}



if [ $2 = f ]; then

echo "Running Full Backup"

echo "-------------------"

fullbackup

exit

        elif [ $2 = i ]; then

        echo "Running Incremental Backup"

        echo "--------------------------"

        incbackup

        exit

                else

echo "usage ./backupscript [username] [f for full or i for incremental]"

fi

exit

sharted

Apr 10th, 2012 6:12 AM

Re: BASH backup script

Hi Carlw,

what happens if you change the command from:

tar -cpfz $TARGETDIR$OUTPUTFILE $SOURCEDIR

tar -cpzf $TARGETDIR$OUTPUTFILE $SOURCEDIR

?

I seem to remember something like the f option must be followed by the archive file... The examples in the man page all show this usage but I wasn't able (skimming through) to see this explicitly stated.

Maybe this is of some help... :icon_neutral:

carlw

Apr 10th, 2012 7:13 AM

Re: BASH backup script

Quote:

Originally Posted by sharted (Post 234174)

Hi Carlw,

what happens if you change the command from:

tar -cpfz $TARGETDIR$OUTPUTFILE $SOURCEDIR

tar -cpzf $TARGETDIR$OUTPUTFILE $SOURCEDIR

There's an issue:
carl@ubuntubox:/mnt/backup$ ls
carlbackup-20120410.tar.gz
carl@ubuntubox:/mnt/backup$ cd
carl@ubuntubox:~$ sudo ./backupscript carl i
Running Incremental Backup
--------------------------
Updating Backup File
tar: Cannot update compressed archives
Try `tar --help' or `tar --usage' for more information.
carl@ubuntubox:~$

My Code:

#!/bin/bash

SOURCEDIR="/home/$1"

TARGETDIR="/mnt/backup/"

OUTPUTFILE=$1backup-$(date +%Y%m%d).tar.gz

USERFILE="$1backup-*.tar.gz"





function incbackup {

echo "Updating Backup File"

tar -uzf $TARGETDIR$USERFILE $SOURCEDIR

}



function fullbackup {

tar -cpzf $TARGETDIR$OUTPUTFILE $SOURCEDIR

}



if [ $2 = f ]; then

echo "Running Full Backup"

echo "-------------------"

fullbackup

exit

        elif [ $2 = i ]; then

        echo "Running Incremental Backup"

        echo "--------------------------"

        incbackup

        exit

                else

echo "usage ./backupscript [username] [f for full or i for incremental]"

fi

exit

sharted

Apr 10th, 2012 7:43 AM

Re: BASH backup script

Ok, I see. You could separate the tar and compression stages of the backup. That way for the incremental procedure, you can just uncompress, update and then recompress. Alternatively, you could not compress the backup at all...

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