Re: root volume backup and devices

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T o n g a wrote :
> Hi, 

Hi,

> 
> What's the best practice dealing with devices when backing up the root
> volume?

Well, my own practice is to backup everything unless it is established
to be useless (temporary or live system related for example):
Thus I usually remove /tmp /var/tmp and the like, as well as /proc and
/dev/pts under Linux and as well as /mnt (which hold the mounting points
of removable media on my system).

so far with dar this makes the following command-line (yes, I am using
dar too ;-) ):
dar -R / -c <somewhere> -P <somewhere> -P tmp -P var/tmp -P proc -P
dev/pts -P mnt

I also remove the many caching directory like this those created by
seamonkey:

- -P "home/*/.mozilla/*/Cache"

For squid I backup the caching at full backup only to avoid having to
manually rebuild the cache directory structure.

Last I also find useful the -D option to not have to manually recreate
all theses ignored directories.

Of course you would also add compression and maybe encryption at your will.

> 
> I used to use the following switches to backup my root volume:
> 
>   -P dev -P proc -P sys --no-mount-points
> 
> I.e., I thought udev would populate /dev on boot up so I didn't back it
> up. However, I got
> 
>  Warning: unable to open initial console
> 
> from the restored system and the boot froze. 
> 
> Having gone through all the possible reasons in http://kerneltrap.org/node/2205
> did I realize that my /dev directory should be backed up & populated.
> In fact, what's really important are the null, zero, console and tty[0-9]
> devices. 
> 
> So if there is no good way dealing with devices, can I use '-P dev' to
> exclude them all at first then include back those important devices? 
> If yes, how?

I do not exclude /dev because I still use a static list of devices (not
using udev). Now, if your are not just with your virtual memory when
doing backup (especially differential backup) with dar, it does not hurt
to backup even devices generated by udev.

To me each thing your remove from a backup is a risk you take for it
avoids your restored system to boot. For this reason I prefer to include
everything except a well defined list of items, and for each having
evaluated the risk I take not to include them (seen the way each is
used). It is also probably a good thing to restore your backup on
another computer (or virtual machine for example) to see if you will be
able to recover your system from backup, before you really need to rely
on your backup for that.

But I guess that you too find this to be obvious. :-)

> 
> Thanks
> 

You're welcome,

Regards,
Denis.
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