A photograph is something that stop the time. Whatever else you do or you change after taking the photo isn't important, because you can always know how the things where at the time of the photo.

A snapshot is the same thing, but related to file and directories. If we take a snapshot of a particular directory or file, we can always access to this file as it was until the snapshot, no matter how much we changed the file or if the file was completely deleted. We can access this type of information at least until we delete the snapshot we took.

The filer that serve the IPG user create these snapshots automatically and in a trasparent fashion, the user's don't have to manage any configuration to activate this feature. Every hour the system generate a snapshot of the user's directory and save it in a separate space (not really, but just to maintain the thing simple). The users can access these data just browsing the homedir, without the need to use some strange and unfriendly software. Maintaining a copy of every modify of a file is impossible, so the snapshots are created at regular intervals every hour and then every day and then every week. With this mechanism the users can access his/hers old file inside an hidden directory named .snapshot resident in their homedir. Inside this directory exists others directories that have name

• hourly.[0-3]
• nightly.[0-3]
• weekly.[0-1]

As the name suggest, these directory contain the file changed during the lasts 4 hours, 4 days and 2 weeks. If the wanted file was deleted/changed during this time, the user have to search these directories, in order to find it. Pay attention that inside the .snapshot directories a user can see the state of his/hers directory how it was, so if you look inside one of these directory you can see not only the files changed, but all the files you have currently. Amazing, isn'it? If the file is found, the users can copy it where it want and the restore is done.

Every user of the LTHC, LTHI and LCM labs can find inside his/hers homedir on the central filer an hidden directory named .snapshot. Inside this directory exists others directories:

ls .snapshot/
hourly.0
hourly.1
hourly.2
hourly.3
nightly.0
nightly.1
nightly.2
nightly.3
weekly.0
weekly.1

As the name suggest, every directory of the list contain the files changed during the lasts 4 hours, 4 days and 2 weeks (the 0 is something). If the wanted file was deleted/changed during this time, the user have to look inside these directories, in order to find it. If the file is found, the users can copy it where it want and the restore is done.

Don't try to use the files directly in the .snapshot dir.

<note warning> Pay attention that inside the .snapshot directories you can see the state of his/hers directory how it was at the time of snaphot, not only the files deleted </note>