NAME¶
s3qllock - Make trees on an S3QL file system immutable
SYNOPSIS¶
s3qllock [options] <directory>
DESCRIPTION¶
S3QL is a file system for online data storage. Before using S3QL, make sure to
consult the full documentation (rather than just the man pages which only
briefly document the available userspace commands).
The
s3qllock command makes a directory tree in an S3QL file system
immutable. Immutable trees can no longer be changed in any way whatsoever. You
can not add new files or directories and you can not change or delete existing
files and directories. The only way to get rid of an immutable tree is to use
the
s3qlrm command.
s3qllock can only be called by the user that mounted the file system and
(if the file system was mounted with
--allow-other or
--allow-root) the root user. This limitation might be removed in the
future (see
issue 155).
RATIONALE¶
Immutability is a feature designed for backups. Traditionally, backups have been
made on external tape drives. Once a backup was made, the tape drive was
removed and locked somewhere in a shelf. This has the great advantage that the
contents of the backup are now permanently fixed. Nothing (short of physical
destruction) can change or delete files in the backup.
In contrast, when backing up into an online storage system like S3QL, all
backups are available every time the file system is mounted. Nothing prevents
a file in an old backup from being changed again later on. In the worst case,
this may make your entire backup system worthless. Imagine that your system
gets infected by a nasty virus that simply deletes all files it can find -- if
the virus is active while the backup file system is mounted, the virus will
destroy all your old backups as well!
Even if the possibility of a malicious virus or trojan horse is excluded, being
able to change a backup after it has been made is generally not a good idea. A
common S3QL use case is to keep the file system mounted at all times and
periodically create backups with
rsync -a. This allows every user to
recover her files from a backup without having to call the system
administrator. However, this also allows every user to accidentally change or
delete files
in one of the old backups.
Making a backup immutable protects you against all these problems. Unless you
happen to run into a virus that was specifically programmed to attack S3QL
file systems, backups can be neither deleted nor changed after they have been
made immutable.
OPTIONS¶
The
s3qllock command accepts the following options:
- --debug
- activate debugging output
- --quiet
- be really quiet
- --version
- just print program version and exit
EXIT STATUS¶
s3qllock returns exit code 0 if the operation succeeded and 1 if some
error occurred.
SEE ALSO¶
The S3QL homepage is at
http://code.google.com/p/s3ql/.
The full S3QL documentation should also be installed somewhere on your system,
common locations are
/usr/share/doc/s3ql or
/usr/local/doc/s3ql.
COPYRIGHT¶
2008-2011, Nikolaus Rath