About SnapShot

Lowell Gilbert freebsd-questions-local at be-well.ilk.org
Mon Oct 3 12:03:14 PDT 2005

"Vahric MUHTARYAN" <vahric at doruk.net.tr> writes:

>             Today I try to learn snapshot with FreeBSD 5.4 , perfect it's
> working very fest . I wonder something if somebody have knowledge about
> snapshot or have a documentation about it I will be happy. 

Did you read the relevant sections of "man mount"?

> First I don't understand How system can take snapshot quickly I tried it on
> new installed freebsd 5.4 and when I gave a command on console snapshot file
> created in a second which 256MB , I wonder How fast will be on bigger
> partitions. Anybody know How snapshot tecnology is working ? Because it's
> creating an single file and it's 256 mb , it's not possible to copy /var
> folder to another folder in a second ... 

Making a snapshot doesn't make copies of the files.  They will only be
copied if a new version is created in the real filesystem.  This is
called "copy on write".  

Technical documentation is probably at http://www.mckusick.com/softdep/

> Second Why I can't create snapshot file on different directory , I tried to
> linking but it didn't work ! 

AS "man mksnap_ffs" says, "The snapshot_name argument must be
contained within the file system mounted at mountpoint."

> And anyway Does it possible to back from snapshot file to original portion
> ... I mean snapshot is creating only one file When I want to backI have to
> mount it to system and copy back files Im asking without copying something
> and mouting snapshot file can I make a restore ? 

No, that isn't possible.

More information about the freebsd-questions mailing list