Re: [Hampshire] Automating rsync to run as root

On Wednesday 12 Sep 2007, Russell Gadd wrote:
> I'd like to ask for advice re a backup system I'm trying to set up
> for Linux. I have given some background which please excuse if it
> seems a bit long.
>
> I have used Windows for many years and have recently decided to try
> to convert to Linux as I don't want to go down the Vista route, so
> I am a Linux greenhorn (apologies in advance for my ignorance). I
> have a boot manager (BootitNG) which allows me to run Windows XP
> (actually 3 different instances - home, work and internet banking)
> and I have installed Debian and Ubuntu alongside these. My goal at
> present is to get beyond the "playing with it" stage to do some
> real work and so I want to first set up a backup system and then
> address some basic security issues (which I need to do more
> research on).
>
> My "daily" backup system will copy my personal files to a folder on
> a separate FAT-32 (VFAT) partition (shared with Windows) and then
> mirror this partition to a second hard drive. Also copy the files
> to a USB stick (permanently connected in a port in the back of the
> PC) - "belt and braces". A "weekly" routine will copy backup files
> to a CD (then stored in my garage separate from the house). I have
> this automated in Windows via an icon on the desktop (running a
> batch command file) which is what I want to achieve in Linux also.
>
> I separate personal files from files which can be recovered if
> necessary from a new install of the OS and software. I backup the
> latter via imaging the OS partitions and mirroring them to the
> second hard drive and occasionally to DVD.
>
> I currently have a simple bash script (my first!) which uses tar
> and rsync. In order to backup onto a VFAT partition I have had to
> use tar to preserve permissions, which seems ok. Although it
> necessitates rewriting all the data not just the changed data, this
> doesn't amount to a lot of stuff.
>
> My problem is with rsync, which I use so that it only needs to
> mirror the files which have changed, since the partitions to mirror
> contain a lot more than just the personal data (e.g. Linux .iso
> images, things stored on DVD, etc). To get it to run from an icon
> on the desktop (Gnome) I have initially resorted to the setuid bit
> to allow rsync to run as root otherwise it refuses to clone the
> partition. However I understand this is not good from a security
> standpoint and I need to find a better solution. It also breaks
> when rsync is updated (via Synaptic) which I found out recently, as
> I presume the executable has been replaced by a newer version so
> the setuid bit would need tweaking again.
>
> Most discussions of backup I have seen talk about using cron, but
> my PC is not on 24/7 and I want to continue my practice of invoking
> the backup routine at the end of a session of work shortly before I
> pull the plug, so either I want to be able to start if from an icon
> on the desktop. Or maybe a script which can be set up to run on
> logoff - I haven't checked into whether this is possible or how to
> do this yet - maybe this could be a root script?. But somehow I
> prefer the manual invocation via an icon.
>
> My current rough idea to solve this is to set up a sort of
> handshake which is maybe a bit clumsy. The desktop icon would run a
> script which sets a flag - just a date/time saved in a text file,
> and there would be a cron script owned by root which runs say once
> per minute to check this file for the latest date/time and perform
> a backup when it sees the date/time is later than the last backup.
> I haven't looked at cron in any detail yet so there may be gotchas
> here. I don't know whether there would be problems with a collision
> if the user script was writing the file when cron is trying to read
> it. Also how would I know when the job has been done and if it
> suceeded ? - maybe the user bash script would need to run
> continuously looking for an end of job handshake from the backup
> script?
>
> I would appreciate comments on this idea or any alternative ideas-
> thanks in advance. Also if I should instead be asking this in some
> other mailing list, please tell me where to go (politely I hope:)
>
> Russell

Hi Russell,

Just some ideas rather than a solution:

If you want to run something manually you can set up a command to run
with root privileges by using su (see 'man su', but roughly:
su root -c "command") There are also GUI versions such as kdesu which
pop up a window to ask for the root password. Also look at sudo which
would allow you to specify certain programs as runnable using your
own password to gain root privileges.

There is a cron-like program called anacron which IIRC handles the
situation of being switched off and spots it's missed something while
asleep.

There is a multitude of backup programs in the Debian archive - my
favourite is backup2l. Have a browse through aptitude or synaptic (I
prefer aptitude as it doesn't need X to be working when things go
wrong)

The default is for cron to send the output from scripts to you by
email if you've got that stuff configured correctly.

HTH, Peter