Linux Backups

I love using the find command. In DOS, find is like grep. In Linux, find is the most powerful recursive DOS dir /s or Linux ls -r command you could ever put your saddle on.

One of the things you can do with find is to avoid directories, using the -prune switch. Like so:

find /usr/local -type d -a \( -name jre1.6.0_38 -prune -o -type d -print \)

Yeah, put your bike helmet on if you keep reading. That spat out a ton of gook. But was I lying? Well, grep out everything but what we should have pruned:

find /usr/local -type d -a \( -name jre1.6.0_38 -prune -o -type d -print \) | grep jre1.6

What if you have a series of subdirectories you want to include, but you cannot write enough -prune switches for them? This is a problem I frequently have. For instance, how do you exclude all your Firefox Cache directories, especially if you have multiple profiles? Great question.

I’d first use find to find all the directories I

do want to backup:

find /home/jed -maxdepth 4 -type d > /tmp/dirlist

Then you grep out things you really don’t want:

egrep -i "/cache|/Trash" /tmp/dirlist > /tmp/avoid

Then parse it into things you do want to find to avoid:

cat /tmp/avoid | while read F ; do echo " -path $F -o " ; done > /tmp/avoid2 ;
echo "-path ./asdf" >> /tmp/avoid2

Now we can refresh our list of directories to descend:

find . -xdev -depth -type d \( `cat /tmp/avoid2` \) -prune -o -print

If we want to turn that right into files, modify the last print statement to find files:

find . -xdev -depth -type d \( `cat /tmp/avoid2` \) -prune -o -type f -print

Now if you want to find the files more recently created than your last backup in /home/backup/monday.tgz, try this:

find . -xdev -depth -type d \( `cat /tmp/avoid2` \) -prune -o -type f -newer /home/backup/monday.tgz -print

Is that enough to make you cry? Chin up, think of all the disk space you’re saving, and how much faster a specific backup can occur. This means you can run backups every 15 minutes.