rsnapshot

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Revision as of 19:19, 28 May 2013 by Mann138 (Talk | contribs) (Remote Systems)

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Summary help replacing me
Instructions on using rsnapshot.

Rsnapshot is an open source utility that provides incremental back ups.

Installation

Install the rsnapshot package using pacman:

# pacman -S rsnapshot

Configuration

In the install process, the config file is created. It is recommended you make a back up of this file in case you need to reconfigure the file again.

# cp /etc/rsnapshot.conf /etc/rsnapshot.conf.default

The rsnapshot.conf config file is well commented, and much of it should be fairly self-explanatory. For a full reference of all the various options, please consult the rsnapshot man page. Type:

# man rsnapshot

Root Directory

Choose the directory where you want to store the file system back ups, in this case I will store the back ups in /mnt/backups/

/etc/rsnapshot.conf
# All snapshots will be stored under this root directory.
#
snapshot_root   /mnt/backups/
Note: Fields are separated by tabs, not spaces. The reason for this is so it's easier to specify file paths with spaces in them.

External program dependencies

Uncomment the lines refering to the unix commands cp, du, ssh (if you want to do remote back ups) and rsnapshot-diff, etc. This section of the file should look like this:

/etc/rsnapshot.conf
# LINUX USERS:   Be sure to uncomment "cmd_cp". This gives you extra features.
# EVERYONE ELSE: Leave "cmd_cp" commented out for compatibility.
#
# See the README file or the man page for more details.
#
cmd_cp          /usr/bin/cp

# uncomment this to use the rm program instead of the built-in perl routine.
#
cmd_rm          /usr/bin/rm

# rsync must be enabled for anything to work. This is the only command that
# must be enabled.
#
cmd_rsync       /usr/bin/rsync

# Uncomment this to enable remote ssh backups over rsync.
#
cmd_ssh /usr/bin/ssh

# Comment this out to disable syslog support.
#
cmd_logger      /usr/bin/logger

# Uncomment this to specify the path to "du" for disk usage checks.
# If you have an older version of "du", you may also want to check the
# "du_args" parameter below.
#
cmd_du          /usr/bin/du

# Uncomment this to specify the path to rsnapshot-diff.
#
cmd_rsnapshot_diff      /usr/local/bin/rsnapshot-diff

# Specify the path to a script (and any optional arguments) to run right
# before rsnapshot syncs files
#
#cmd_preexec    /path/to/preexec/script

# Specify the path to a script (and any optional arguments) to run right
# after rsnapshot syncs files
#
#cmd_postexec   /path/to/postexec/script
Note: cmd_preexec and cmd_postexec are custom scripts to be run before and after each run of rsnapshot

Backup Intervals

rsnapshot has no idea how often you want to take snapshots. In order to specify how much data to save, you need to tell rsnapshot which intervals to keep, and how many of each. An interval, in the context of the rsnapshot config file, is a unit of time measurement. These can actually be named anything (as long as it's alphanumeric, and not a reserved word), but by convention we will call ours hourly and daily. In this example, we want to take a snapshot every four hours, or six times a day (these are the hourly intervals). We also want to keep a second set, which are taken once a day, and stored for a week (or seven days). This happens to be the default, so as you can see the config file reads:

/etc/rsnapshot.conf
interval    hourly  6
interval    daily   7

Back up

This is the section where you tell rsnapshot what files you actually want to back up. You put a “backup” parameter first, followed by the full path to the directory or network path you're backing up. The third column is the relative path you want to back up to inside the snapshot root.

/etc/rsnapshot.conf
###############################
### BACKUP POINTS / SCRIPTS ###
###############################

# LOCALHOST
backup  /home/          localhost/

In this example, backup tells us it's a backup point. /etc/ is the full path to the directory we want to take snapshots of, and localhost/ is a directory inside the snapshot_root we're going to put them in. Using the word localhost as the destination directory is just a convention. You might also choose to use the server's fully qualified domain name instead of localhost. If you are taking snapshots of several machines on one dedicated backup server, it's a good idea to use their various hostnames as directories to keep track of which files came from which server.

Remote Systems

In addition to full paths on the local filesystem, you can also backup remote systems using rsync over ssh. If you have ssh installed and enabled (via the cmd_ssh parameter), you can specify a path like:

/etc/rsnapshot.conf
###############################
### BACKUP POINTS / SCRIPTS ###
###############################

# example.com
backup      root@example.com:/etc/     example.com/

This behaves fundamentally the same way, but you must take a few extra things into account:

  • The ssh daemon must be running on example.com
  • You must have access to the account you specify the remote machine, in this case the root user on example.com.
  • You must have key-based logins enabled for the root user at example.com, without passphrases. If you wanted to perform backups as another user, you could specify the other user instead of root for the source (i.e. user@domain.com). Please note that allowing remote logins with no passphrase is a security risk that may or may not be acceptable in your situation. Make sure you guard access to the backup server very carefully! For more information on how to set this up, please consult the ssh man page, or a tutorial on using ssh public and private keys. You will find that the key based logins are better in many ways, not just for rsnapshot but for convenience and security in general. One thing you can do to mitigate the potential damage from a backup server breach is to create alternate users on the client machines with uid and gid set to 0, but with a more restrictive shell such as scponly.
  • This backup occurs over the network, so it may be slower. Since this uses rsync, this is most noticeable during the first backup. Depending on how much your data changes, subsequent backups should go much, much faster since rsync only sends the differences between files.