NILFS on Jaunty

The latest release of Ubuntu includes the long awaited Ext4 FS (works flawlessly on my system).
Ext4 is faster & more secure but still lacks the ability to manage FS snapshots (ZFS excels in that, but runs only in FUSE on linux).
An interesting alternative is NILFS:

NILFS is a log-structured file system supporting versioning of the entire file system and continuous snapshotting which allows users to even restore files mistakenly overwritten or destroyed just a few seconds ago.

NILFS maintains a repo for Hardy, the Jaunty repos contain only the user land tools which won't do us much good since we need the kernel module as well, this leaves us only with the option of installing it from source (still quite easy).

# a perquisite
$ sudo aptitude install uuid-dev  
# installing kernel module, result module resides in /lib/modules/2.6.28-11-generic/kernel/fs/nilfs2/nilfs2.ko
$ wget http://www.nilfs.org/download/nilfs-2.0.12.tar.bz2
$ tar jxf nilfs-2.0.12.tar.bz2
$ cd nilfs-2.0.12
$ make
$ sudo make install
# installing user land tools
$ wget http://www.nilfs.org/download/nilfs-utils-2.0.11.tar.bz2
$ tar jxf nilfs-utils-2.0.11.tar.bz2
$ cd nilfs-utils-2.0.11
$ ./configure
$ make 
$ sudo make install

Creating a file system on a file (ideal for playing around):

$ dd if=/dev/zero of=mynilfs bs=512M count=1
$ mkfs.nilfs2 mynilfs

The FS is only a mount away:

# mounting the file as a loop device
$ sudo losetup /dev/loop0 mynilfs
$ sudo mkdir /media/nilfs
$ sudo mount -t nilfs2 /dev/loop0 /media/nilfs/

Now lets create a couple of files:

$ cd /media/nilfs
$ touch 1 2 3 
# listing all checkpoints & snapshots, on your system list should vary 
$ lscp
                  CNO        DATE     TIME  MODE  FLG   NBLKINC       ICNT
                   7  2009-05-01 01:08:09   ss    -         12          6
                  13  2009-05-01 19:05:34   cp    i          8          3
                  14  2009-05-01 19:05:59   cp    i          8          3
                  15  2009-05-01 19:07:09   cp    -         12          6
# creating a snapshot
$ sudo mkcp -s
# 15 is the new snapshot (mode is ss)
$ lscp 
                 CNO        DATE     TIME  MODE  FLG   NBLKINC       ICNT
                   7  2009-05-01 01:08:09   ss    -         12          6
                  13  2009-05-01 19:05:34   cp    i          8          3
                  14  2009-05-01 19:05:59   cp    i          8          3
                  15  2009-05-01 19:07:09   ss    -         12          6
                  16  2009-05-01 19:08:59   cp    i          8          6

# our post snapshot file
$ touch 4

Now lets go back in time into our snapshot, NILFS enables us to mount old snapshots as read only FS (while the original FS is still mounted):

$ sudo mkdir /media/nilfs-snapshot
$ sudo mount.nilfs2  -r  /dev/loop0 /media/nilfs-snapshot/ -o cp=15 # only snapshots works!
$ cd /media/nilfs-snapshot
# as we might expect
$ ls 
 1 2 3 

NILFS has some interesting features, its not production ready yet however it sure worth looking after its development.