Q. I’ve HP RAID 6 server running RHEL 5.x. I’d like to act this box as a backup server for my other Red Hat DNS and Web server. The server must keep backup in hourly, daily and monthly format. How do I configure my Red Hat / CentOS Linux server as remote backup or snapshot server?

A. rsnapshot is easy, reliable and disaster recovery backup solution. It is a remote backup program that uses rsync to take backup snapshots of filesystems. It uses hard links to save space on disk and offers following features:

• Filesystem snapshot – for local or remote systems.
• Database backup – MySQL backup
• Secure – Traffic between remote backup server is always encrypted using openssh
• Full backup – plus incrementals
• Easy to restore – Files can restored by the users who own them, without the root user getting involved.
• Automated backup – Runs in background via cron.
• Bandwidth friendly – rsync used to save bandwidth

Sample setup

• snapshot.example.com – HP box with RAID 6 configured with Red Hat / CentOS Linux act as backup server for other clients.
• DNS ns1.example.com – Red Hat server act as primary name server.
• DNS ns2.example.com – Red Hat server act as secondary name server.
• www.example.com – Red Hat running Apache web server.
• mysql.example.com – Red Hat mysql server.

Install rsnapshot

Login to snapshot.example.com. Download rsnapshot rpm file, enter:

WARNING! These examples only works on Red hat / CentOS / Suse / RHEL / Fedora Linux. See Debian / Ubuntu Linux backup server instructions here.

# cd /tmp
# wget http://www.rsnapshot.org/downloads/rsnapshot-1.3.0-1.noarch.rpm
# wget http://www.rsnapshot.org/downloads/rsnapshot-1.3.0-1.noarch.rpm.md5
Verify rpm file for integrity, enter
# md5sum -c rsnapshot-1.3.0-1.noarch.rpm.md5
Sample output:

rsnapshot-1.3.0-1.noarch.rpm: OK

Install rsnapshot, enter:
# rpm -ivh rsnapshot-1.3.0-1.noarch.rpm
Sample output:

Preparing...                ########################################### [100%]
   1:rsnapshot              ########################################### [100%]

Configure rsnapshot

You need to perform following steps

Step # 1: Configure password less login

To perform remote backup you need to setup password less login using openssh. Create ssh rsa key and upload they to all servers using scp (note you are overwriting ~/ssh/authorized_keys2 files). You need to type following commands on snapshot.example.com server:
# ssh-keygen -t rsa
# scp .ssh/id_rsa.pub [email protected]:.ssh/authorized_keys2
# scp .ssh/id_rsa.pub [email protected]:.ssh/authorized_keys2
# scp .ssh/id_rsa.pub [email protected]:.ssh/authorized_keys2
# scp .ssh/id_rsa.pub [email protected]:.ssh/authorized_keys2

Step # 2: Configure rsnapshot

The default configuration file is located at /etc/rsnapshot.conf. Open configuration file using a text editor, enter:
# vi /etc/rsnapshot.conf

Configuration rules

You must follow two configuration rules:

• rsnapshot config file requires tabs between elements.
• All directories require a trailing slash. For example, /home/ is correct way to specify directory, but /home is wrong.

First, specify root directory to store all snapshots such as /snapshots/ or /dynvol/snapshot/ as per your RAID setup, enter:

snapshot_root	/raiddisk/snapshots/

You must separate snapshot_root and /raiddisk/snapshots/ by a [tab] key i.e. type snapshot_root hit [tab] key once and type /raiddisk/snapshots/.

Define snapshot intervals

You need to specify backup intervals i.e. specify hourly, daily, weekly and monthly intervals:

interval	hourly	6
interval	daily	7
interval	weekly	4
interval	monthly	3

The line “interval hourly 6” means 6 hourly backups a day. Feel free to adapt configuration as per your backup requirements and snapshot frequency .

Remote backup directories

To backup /var/named/ and /etc/ directory from ns1.example.com and ns2.example.com, enter:

backup	[email protected]:/etc/	ns1.example.com/
backup	[email protected]:/var/named/	ns1.example.com/
backup	[email protected]:/etc/	ns2.example.com/
backup	[email protected]:/var/named/	ns2.example.com/

To backup /var/www/, /var/log/httpd/ and /etc/ directory from www.example.com, enter

backup	[email protected]:/var/www/	www.example.com/
backup	[email protected]:/etc/	www.example.com/
backup	[email protected]:/var/log/httpd/	www.example.com/

To backup mysql database files stored at /var/lib/mysql/, enter:

backup	[email protected]:/var/lib/mysql/	mysql.example.com/dbdump/

Save and close the file. To test your configuration, enter:
# rsnapshot configtest
Sample output:

Syntax OK

Schedule cron job

Create /etc/cron.d/rsnapshot cron file. Following values used correspond to the examples in /etc/rsnapshot.conf.

0 */4 * * *         /usr/bin/rsnapshot hourly
50 23 * * *         /usr/bin/rsnapshot daily
40 23 * * 6         /usr/bin/rsnapshot weekly
30 23 1 * *         /usr/bin/rsnapshot monthly

Save and close the file. Now rsnapshot will work as follows to backup files from remote boxes:

1. 6 hourly backups a day (once every 4 hours, at 0,4,8,12,16,20)
2. 1 daily backup every day, at 11:50PM
3. 1 weekly backup every week, at 11:40PM, on Saturdays (6th day of week)
4. 1 monthly backup every month, at 11:30PM on the 1st day of the month

How do I see backups?

To see backup change directory to
# cd /raiddisk/snapshots/
# ls -l
Sample output:

drwxr-xr-x 4 root root 4096 2008-07-04 06:04 daily.0
drwxr-xr-x 4 root root 4096 2008-07-03 06:04 daily.1
drwxr-xr-x 4 root root 4096 2008-07-02 06:03 daily.2
drwxr-xr-x 4 root root 4096 2008-07-01 06:02 daily.3
drwxr-xr-x 4 root root 4096 2008-06-30 06:02 daily.4
drwxr-xr-x 4 root root 4096 2008-06-29 06:05 daily.5
drwxr-xr-x 4 root root 4096 2008-06-28 06:04 daily.6
drwxr-xr-x 4 root root 4096 2008-07-05 18:05 hourly.0
drwxr-xr-x 4 root root 4096 2008-07-05 15:06 hourly.1
drwxr-xr-x 4 root root 4096 2008-07-05 12:06 hourly.2
drwxr-xr-x 4 root root 4096 2008-07-05 09:05 hourly.3
drwxr-xr-x 4 root root 4096 2008-07-05 06:04 hourly.4
drwxr-xr-x 4 root root 4096 2008-07-05 03:04 hourly.5
drwxr-xr-x 4 root root 4096 2008-07-05 00:05 hourly.6
drwxr-xr-x 4 root root 4096 2008-07-04 21:05 hourly.7
drwxr-xr-x 4 root root 4096 2008-06-22 06:04 weekly.0
drwxr-xr-x 4 root root 4096 2008-06-15 09:05 weekly.1
drwxr-xr-x 4 root root 4096 2008-06-08 06:04 weekly.2

How do I restore backup?

Let us say you would like to restore a backup for www.example.com. Type the command as follows (select day and date from ls -l output):
# cd /raiddisk/snapshots/
# ls -l
# cd hourly.0/www.example.com/
# scp -r var/www/ [email protected]:/var/www/
# scp -r etc/httpd/ [email protected]:/etc/httpd/

How do I exclude files from backup?

To exclude files from backup, open rsnapshot.conf file and add following line:

exclude_file	/etc/rsnapshot.exclude.www.example.com

Create /etc/rsnapshot.exclude.www.example.com as follows:

/var/www/tmp/
/var/www/*.cache

Further readings:

1. man rsnaspshot, ssh, ssh-keygen