dump(8), incremental backups, Tower of Hanoi sequence, don't get it

[Alex Zbyslaw]

Ilari Laitinen wrote:

>On Fri, Aug 19, 2005 at 04:22:20PM +0100, Alex Zbyslaw wrote:
>  
>
>This pretty much cleared it up. Now that I read the manual page again,
>enlightened, it seems quite easy to follow. Nice.
>
>Using the algorithm above I get the following:
>
>Sequence                Dumps needed
>0 3                     0 3
>0 3 2                   0 2
>0 3 2 5                 0 2 5
>0 3 2 5 4               0 2 4
>0 3 2 5 4 7             0 2 4 7
>0 3 2 5 4 7 6           0 2 4 6
>0 3 2 5 4 7 6 9         0 2 4 6 9
>0 3 2 5 4 7 6 9 8       0 2 4 6 8
>0 3 2 5 4 7 6 9¹8 9²    0 2 4 6 8 9²
>
>Am I doing this right? Every time a dump of level N is, eh, taken,
>earlier tapes of level >N become obsolete and are free to go(*). In this
>case, that happens every other time.
>
>(*) Unless one would like to have those file versions around for a
>    longer time, of course.
>  
>
Yes, that looks correct.  Like I said, for a lightly used computer you 
might want to keep it simpler.  It really depends how *big* the files 
which change are and how big your backup disk is compared to your real 
one.  You can figure out what was dumped on each backup using "restore 
-ivf {path_to_backup}" and typing "ls"* at the prompt.  A simpler scheme 
makes it easier to find a random single file which you deleted by 
accident, as opposed to recovering your whole disk.

If you are backing up to disk, then you could also consider compressing 
you backups.  Instead of doing

dump -NuaL -f [path_to_backup]

you could do

dump -Nual -f - | gzip -9 > [path_to_backup].gz


Then to check what is on it:

gunzip -9 [path_to_backup].gz | restore -ivf -

(*) Actually, that will just show the top level directories.  What you 
get is a *very* simple shell with ls, cd and a few restore specific 
options.  Depressingly, restore isn't set up to use the readline 
library, so you get no command editing.

>>clip
>>
>>I would also consider doing your backups daily, not weekly as your 
>>example suggests.  The timing of full backups depends on how busy your 
>>machine is.  Anything from weekly to quarterly.
>>    
>>
>
>Well, I am the only active user on this computer. And I know when there
>is something to back up, so it will be a bit irregular in reality. If I
>only surf the Net all weekend long, there is nothing to worry about. Or
>if I am not physically around, the computer will have no power to mess
>with.
>  
>
That's fine.  Certainly nothing changes when the machine is off :-)  
Beware of "I was just surfing the net" though, as you may have had email 
coming in, and have bookmarked somewhere that you'll never manage to 
find again :-)  Regrettably, even trivial sessions can generate 
important data.  But like you say, that's your call.  From experience I 
know that there is a strong tendency for laziness to kick in.

--Alex