Re: Home made backup system

[rhkramer@gmail.com]

Thanks to all who replied!

This script (or elements of it) looks useful to me, but I don't fully 
understand it -- I plan to work my way through it -- I have a few questions 
now, I'm sure I will have more after I get past the first 3 (or more 
encouraging to me, first 6) lines.

Questions below:

On Wednesday, December 18, 2019 12:26:04 PM tomas@tuxteam.de wrote:
> On Wed, Dec 18, 2019 at 12:02:56PM -0500, rhkramer@gmail.com wrote:

>   #!/bin/bash
>   home=${HOME:-~}

What does that line do, or more specifically, what does the :-~ do -- note the 
following:

rhk@s19:/rhk/git_test$ echo ${HOME:-~}
/home/rhk
rhk@s19:/rhk/git_test$ echo ${HOME}
/home/rhk

>   if test -z "$home" -o \! -d "$home" ; then

What does the -o \! do -- hmm, I guess \! is a bash "refeence" to the owner -- 
I guess I should look for it in man bash...

Hmm, but that means (in bash) the "history number" of the command

"              \!     the history number of this command"

>     echo "can't backup the homeless, sorry"
>     exit 1
>   fi

I'm sure I'll have more questions as I continue, but that is enough for me for 
tonight.

>   backup=/media/backup/${home#/}
>   rsync -av --delete --filter="merge $home/.backup/filter" $home/ $backup/
>   echo -n "syncing..."
>   sync
>   echo " done."
>   df -h
> 
> I mount an USB stick (currently 128G) on /media/backup (the stick has a
> LUKS encrypted file system on it) and invoke backup.
> 
> The only non-quite obvious thing is the option
> 
>   --filter="merge $home/.backup/filter"
> 
> which controls what (not) to back up. This one has a list of excludes
> (much shortened) like so
> 
>   - /.cache/
>   [...much elided...]
>   - /.xsession-errors
>   - /tmp
>   dir-merge .backup-filter
> 
> The last line is interesting: it tells rsync to merge a file .backup-filter
> in each directory it visits -- so I can exclude huge subdirs I don't need
> to keep (e.g. because they are easy to re-build, etc.).
> 
> One example of that: I've a subdirectory virt, where I keep virtual images
> and install media. Then virt/.backup-filter looks like this:
> 
>   + /.backup-filter
>   + /notes
>   - /*
> 
> i.e. "just keep .backup-filter and notes, ignore the rest".
> 
> This scheme has served me well over the last ten years. It does have its
> limitations: it's sub-optimal with huge files, it won't probably scale
> well for huge amounts of data.
> 
> But it's easy to use and easy to understand.
> 
> Cheers
> -- t