Re: Another HAMMER crash

[Michael Neumann <mneumann@xxxxxxxx>]

Matthew Dillon wrote:
> :Yes, that helped.
> :
> :>     I recommend always doing a normal mount and using cd @@0x<TID> to
> :>     push into a snapshot.
> :
> :I had no snapshot. I just wanted to try the as-of mount. I read the
> :manual but failed to understand it. hammer(5) says:
> :
> :'Prior versions of files or directories are accessible by appending @@
> :and a transaction ID to the name.'
> :
> :I could not access them this way.
> :
> :-- 
> :Gergo Szakal MD <bastyaelvtars@gmail.com>
> :University Of Szeged, HU
>
>     You can generate the transaction ids manually using 'hammer synctid',
>     or you can extract them from a file using 'undo -i <filename>'.  You
>     get a snapshot every 30-60 seconds even if you don't lift a finger,
>     but unless you record the transaction ids somewhere you'd have to
>     do some sleuthing (e.g. with undo -i) to get them.
>
>     Typically what you would do is have a cron job create a convenient
>     snapshot softlink once an hour, once a day, whatever, like this:
>
>     mkdir /mnt/snapshots
>     hammer snapshot /mnt/snapshots

The first argument to "hammer snapshot" takes a template similar to
strftime(3), so you can generate snapshots with:

  hammer snapshot /mnt/snaphots/SNAP-%Y-%M-%H

Which would generate a symlink

  /mnt/snapshots/SNAP-2008-08-25

If /mnt/snapshots itself is not on a hammer filesystem you should as
well specify the hammer filesystem to snapshot:

  hammer snapshot /mnt/snaphots/SNAP-%Y-%M-%H /hammer

Regards,

  Michael