HowTos:Restore files from snapshots on Linux from home directory on Math file server
These directions describe how to restore recently deleted files or older copies of recently modified files located on the Math/PACM fileserver, e.g. in your home directory. These instructions do not apply if you are trying to restore files located on your own laptop or desktop.
In order to restore files deleted or changed within last few days you can use snapshots, as long as the file you are looking for is located somewhere under your home directory. A snapshot is a read-only image of the entire file system (home directories) that reflects the state of the file system at the time the snapshot was created.
Currently, there are four daily and eleven hourly snapshots. Daily snapshots are created at midnight of every day and four of them are kept, e.g. if you are looking at snapshots at 3pm of Friday you will find daily snapshots created at midnight of previous Monday, Tuesday, Wednesday and Thursday - called, respectively, nightly.3, nightly.2, nightly.1 and nightly.0.
Hourly snapshots are created every two hours, except at midnight, and up to 11 are kept. Hourly snapshots are taken at 2am, 4am, 6am, 8am, 10am, 12pm, 2pm, 4pm, 6pm, 8pm and 10pm. E.g. if you are looking at hourly snapshots at 3pm of Friday you will find hourly snapshots from 2pm Friday, 12pm Friday, 10am Friday, 8am Friday, 6am Friday, 4am Friday, 2am Friday, 10pm Thursday, 8pm Thursday, 6pm Thursday and 4pm Thursday (called hourly.0, hourly.1, ..., hourly.10 respectively).
Note that your deleted or changed file will be in one of the snapshots only if it was on the file system at one of the times when snapshots were taken. E.g. if you create a file at 2:15pm but delete it at 3:40pm then you will not be able to find it and restore it from any of the snapshots (as they were created at 2pm and 4pm and file was not there at either of those times).