Brioche Backup

Table of contents

1   Abstract

Brioche is yet another backup shell script. Its main features are

2   Rationale

Large numbers of backup solutions are freely available today, but when playing with incremental or differential backups, most of them rely on some filesystem capabilities, like hard-linking. If the only remote location available to store the backups is an FTP server, this is not a solution. Brioche relies on GNU tar's --listed-incremental option to create real differential [1] archives.

A second feature that makes Brioche interresting is the ability to use LVM snapshots. In the case of a Xen setup where the domUs use logical volumes as partitions, Brioche is able to backup everything from the dom0.

[1]Each differential backup is based upon the last full backup, unlike incremental, which are based upon the last (full or incremental) backup.

3   Getting Brioche

Download brioche-1.1.tar.gz

You can download the tarball from http://www.alrj.org/pages/brioche.html or get the latest development version with the following git command:

git clone http://git.alrj.org/git/brioche.git

A gitweb interface is also available at http://git.alrj.org/

4   Requirements

Brioche relies on a few easily available free software :

See the References section for links to the aforementioned softwares.

5   Installation

Copy the three files brioche, brioche.conf and briochetab where you like, and set the CONFIG_FILE variable in the brioche script accordingly. If needed, run chmod +x /path/to/brioche. In a typical setup, the brioche script will be put in /usr/local/bin with the other two files under /etc.

6   Using Brioche

6.1   Configuration

Edit the file brioche.conf to suit your needs. Each option is commented inline and will be detailed here.

BACKUPTAB
Full absolute path to the briochetab file. This file describes which logical volumes and partitions must be backed up. Its format is explained in the Defining backups section.
MAILTO
When the job is done, Brioche will send a summary of the operations by email. You can set it to any value that your mail command understands.
REPODIR
Brioche will store all the generated archives in this directory.Note that before doing a full backup, Brioche will move all previous archives into an "undo" subdirectory, which will be removed only if the backup is successful. Make sure there's enough free space on the device where REPODIR is located.
USAGE_WARN
The report email will include a warning if the space used on REPODIR goes beyond the given threshold. The value must be an integer.
COMPRESS
This directive allows to specify the compression method to apply to the archives. Possible values are "none", "gz", "bz2" and "lzma". Warning : lzma may not be available with older versions of GNU tar.
TAR_OPTS
Additionnal options that you may want to pass to tar. A typical value could be "--one-file-system -S". The first option will skip all other mointpoints (very usefull if you have /dev, /proc, /sys or REPODIR mounted under a device that must be archived). The second one will try to deal with sparse files.
SNAPSHOT_MOUNTPOINT
Sets the directory where the temporary LVM snapshots must be mounted.
SNAPSHOT_NAME
The name to use for the snapshot volumes.
SNAPSHOT_SIZE
Set the size of the snapshot volume. The same suffix than for lvcreate(8) are available.
USE_FTP
If set to "yes", Brioche will upload the backups on an FTP server. See the Using FTP section for more information about this feature.
FTP_HOST
The address of the FTP server.
FTP_DIR
The base directory on the FTP server under which all the archives will be stored. Brioche will never touch anything that is not below this directory.
FTP_KEEP
Tells Brioche to keep a certain amount of older runs on the FTP. A run is a full backup plus all its subsequent differential backups. See the Using FTP section for a more detailed explanation.

6.2   Defining backups

The backups are defined in the file birochetab. Here is a typical example for a Xen config where cottman is the dom0 and syrtis, kadarin, valeron are domUs:

# Partition or LV           Snapshot    Host name     Volume name
# ---------------------------------------------------------------
/                           no          cottman       root
/usr                        no          cottman       usr

/dev/vg00/valeron-root      yes         valeron       root

/dev/vg00/kadarin-root      yes         kadarin       root
/dev/vg00/kadarin-home      yes         kadarin       home

/dev/vg00/syrtis-root       yes         syrtis        root
/dev/vg00/syrtis-home       yes         syrtis        home
/dev/vg00/syrtis-usr        yes         syrtis        usr
/dev/vg00/syrtis-var        yes         syrtis        var

Blank lines, or lines beginning with # are ignored.

The first column defines the directory or logical volume to backup. In this example,the first two lines are plain directories, while the other ones point to LVM devices.

The second column specify if the backup should be taken from an LVM snapshot or not. It must be set to "no" for the backup of a directory and to "yes" for the backup of a logical volume.

The last two columns are more or less cosmetic, and define where the archive files will be stored, and how they'll be named. The destination directory will be created under the REPODIR, and its name will be the value on the third column. Inside this directory, archive files will be named from the value given in the fourth column. Grouping by domUs' hostnames is only a suggestion, it can be completely different and adapted to suit your needs.

For instance, a full and a differential backup for the host valeron of the previous example would lead to the following structure:

user:/REPODIR$ ls -l valeron/
total 356544
-rw-r--r-- 1 root root 363545613 Jan  3 03:10 root.full.20090103.tar.bz2
-rw-r--r-- 1 root root    504722 Jan  3 03:10 root.full.snar
-rw-r--r-- 1 root root    504725 Jan  4 04:06 root.incr.20090104.snar
-rw-r--r-- 1 root root    160542 Jan  4 04:06 root.incr.20090104.tar.bz2

WARNING !

In case your REPODIR is not on a distinct device, it will be included in the backup if you've included the device in your briochetab.

To avoid this issue, you can either exclude it explicitely by adding an "--exclude=..." option in TAR_OPTS, or simply specify in your briochetab file which directories need to be archived.

6.3   Using FTP

With the help of lftp, Brioche is able to store an history of backups on an FTP server. This is mainly usefull when no other distant repository is available. If possible, consider using an CIFS, NFS, sshfs or any other kind of remote mountpoint for your REPODIR.

The archives present in the local REPODIR will be mirrored to the FTP server after each backup, be it a full or a differential one.

Since there is no way to hide the credentials if they are passed to lftp on the command line, the authentication relies on your .netrc file. See man netrc(5) for more information. In the home directory of the user that runs Brioche (typically root's), create the .netrc file with the following lines:

machine ftp.example.com
login username
password SikRet

Don't forget to secure it with chmod 600 .netrc or lftp will refuse to use it. The machine name must match the FTP_HOST configuration directive in brioche.conf.

On the FTP server, Brioche will keep a configurable amount of runs. Each run consists of a full backup and all the differential backups that are based on it. Before doing a full backup, Brioche will rotate the runs and keep only the configured number of older backups. The current backups can always be found under /FTP_DIR/hostname/latest/. Older ones will be under /FTP_DIR/hostname/run-X/ with X equal to 1 for the previous run, 2 for the one before and so forth, up to the value of FTP_KEEP.

Here's what happens during the rotation:

  • the oldest run is removed
  • all the run-X/ directories are shifted (run-3/ becomes run-4/, etc)
  • the latest/ directory is renamed to run-1/
  • a new, empty, latest/ directory is created, ready to accept the new files.

6.4   Running Brioche

Brioche understands the following arguments:

-f, --full Do a full backup (by default, brioche will try to do a differential).
-h, --help Show a very limited help.

When everything is ready, execute the brioche script as root. The script is pretty verbose, so don't panic if you see lots of lines scrolling in your terminal. By default, Brioche will try to make differential backups, but will gracefully fall back and do a full backup if none is available.

If all is fine, it can be added in the system crontab. Here's a suggestion for weekly full backup on Sunday, with differential during the weekdays:

# Daily incremental backup
30  3  *  *  1-6  /usr/local/bin/brioche > /var/log/backup.`dow`.log 2>&1
# Weekly full backup on Sunday
30  3  *  *  0  /usr/local/bin/brioche -f > /var/log/backup.`dow`.log 2>&1

The output of the script will be saved in /var/log/backup.DOW.log with DOW being the abbreviated day of the week (see man date(1) for the format). The dow bash script is provided alongside Brioche.

7   Bug reporting

There's no bugtracker for this project, your bug reports should be sent to the author : Amand Tihon <amand.tihon@alrj.org>. Please include as much information as possible in your report.

8   References

social