Table of Contents
Status: Deprecated #
This article covers a version of CentOS that is no longer supported. If you are currently operating a server running CentOS 6, we highly recommend upgrading or migrating to a supported version of CentOS.
CentOS 6 reached end of life (EOL) on November 30th, 2020 and no longer receives security patches or updates. For this reason, this guide is no longer maintained.
This guide might still be useful as a reference, but may not work on other CentOS releases. If available, we strongly recommend using a guide written for the version of CentOS you are using.
The following DigitalOcean tutorial may be of immediate interest, as it provides a general outline of how to use rsync to sync a local directory with remote ones:
How To Use Rsync to Sync Local and Remote Directories
This article provides a quick way to backup the most common things in a typical web hosting scenario: website files and database data. We will setup a full daily backup of a website folder and a copying of this data to a remote server (this can also work for another VPS). We will also set up a rsync example to just copy the incremental changes. Finally, we’ll set up backup of a MySQL database. The procedures described use a few simple Bash commands, rsync and cron to schedule backups. For example data, we can install WordPress as per this
tutorial. It will place WordPress in
/var/www/wordpress directory and a MySQL database
wordpress and we now want to take a backup of all the data.
DigitalOcean provides Snapshots
and Backups, to handle backups and snapshots very well. There are
also excellent backup-as-a-service solutions that work with the
minimum configuration. But sometimes we want to use another backup
server or perhaps an inhouse server, and we want a quick way to pull
the data from webhost back to our server. In that case, these tips can
There are two ways to do backup: incremental and full backups. A full
backup copies all the data, while the snapshot only handles the
changes since the last update.
Full Backup #
Full backup typically does the following:
Make an archive of all the files in a folder
Copy the resulting archive to a remote server.
As noted, our data will reside in /var/www/wordpress directory. We will designate a backup folder location.
mkdir -p /backup/wordpress
The above command will create a /backup directory, and a
/backup/wordpress directory, if they do not exist. To create a full
snapshot of our data, we use the linux tool called tar.
tar -czf /backup/wordpress/initial_backup.tar.gz /var/www/wordpress
Tar will create a gzip archive in a
file initial_backup.tar.gz. We could add a
v flag (so we get tar -czvf) if we want a
verbose output (list of filenames). We name the file
initial_backup.tar.gz so that we know that this is an initial backup,
it is archived with tar and iz is zipped in a gzip format. Tar will
use whatever arguments we provide as a source, in our case it will
backup /var/www/wordpress directory. We could pass two or
more arguments, whether they be files or folders: ie.
tar -czf /backup/cms_systems_backup.tar.gz /var/www/wordpress /var/www/drupal /var/www/joomla
The last command would backup all of our installed cms systems.
Now, for our future backups, we may want to add a date when the backup
tar -czf /backup/wordpress/wordpress-`date '+%m%d%y'`.tar.gz /var/www/wordpress
Lets’ see what we have now:
[root@Backup ~]# ls -l /backup/wordpress/ total 9760 -rw-r--r-- 1 root root 4995743 Apr 17 12:16 initial_backup.tar.gz -rw-r--r-- 1 root root 4995743 Apr 17 12:25 wordpress-041713.tar.gz [root@Backup ~]#
We have two files, one called initial_backup, one called
wordpress-041713 (for April 17th 2013, the time of this writing). Now,
to schedule this daily, we need to create a crontab entry. Crontab is
a linux task scheduler: we tell it when to do something and what task
to actually do. Anyway, we open up the crontab editor:
EDITOR=nano crontab -e
It will open a crontab file in a text editor. By default, DO CentOS
images include vim as editor, which requires a bit of setup, so we
have used a simpler editor for this purpose, called nano editor. We
could have just used the default editor with:
Now we need to tell cron to backup, say, every day at 3.30am, when
there is hopefully not a lot of traffic. We will also tell it to email
us any findings. We put this content into crontab:
MAILTOfirstname.lastname@example.org 30 3 * * * /bin/tar -czf /backup/wordpress/wordpress-`date +%m%d%y`.tar.gz /var/www/wordpress
We save the file with CTRL-X and confirm with Y and Enter. The above
command will tell linux to repeat our command every day at 3:30. We
also told cron to email us with the results. You will receive the
message: /bin/tar: Removing leading `/’ from member names, as
a sign that everything went through. In case of errors, the message
will contain the details so we can fix this. So, a daily backup is
ready and working.
Copy the Backups to Another Remote Server #
To copy the backups to another remote server, we will use scp – secure copy.
First, we need to generate an SSH key:
We can leave the passphrase empty for now, and use the
/root/.ssh/id_rsa_backup key file (or
/home/username/.ssh/id_rsa_backup if we’re not running as root).
Now we can check the public key part:
We need to copy this public part of SSH key to the remote server, to a
file authorized_keys. I assume we already have a remote server called
backup.example.com and a user backup. This could be
an empty newly created DigitalOcean VPS (droplet), but the user has to be created
beforehand. We will only do this part once.
scp .ssh/id_rsa_backup.pub email@example.com:/home/backup/backup_key.pub
We’ll be prompted for the backup users’ password. We copied the file,
now let’s add it where it should be, in authorized_keys. I cannot
assume that this user already has the file and folder set up, so lets
check that info:
ssh firstname.lastname@example.org "mkdir -p /home/backup/.ssh" ssh email@example.com "chmod 700 /home/backup/.ssh" ssh firstname.lastname@example.org "touch /home/backup/.ssh/authorized_keys" ssh email@example.com "chmod 600 /home/backup/.ssh/authorized_keys" ssh firstname.lastname@example.org "mkdir -p /home/backup/backups"
The few commands above created a directory for SSH to work with, if it
didn’t exist, and also the authorized_keys file, which needs to be
present for backups to work. We also created a backups
directory to store our files to. Now what is left is to copy our
public key to that file.
ssh email@example.com "cat /home/backup/backup_key.pub >> /home/backup/.ssh/authorized_keys"
Now we can use this key to copy stuff in the future.
Now, let’s copy the backup file over there:
scp -i .ssh/id_rsa_backup /backup/wordpress/wordpress-041713.tar.gz firstname.lastname@example.org:/home/backup/backups
If our key setup was correct, the file will be copied and we won’t be
asked for passwords. We can check that the file is really there:
ssh email@example.com "ls -l /home/backup/backups"
Ok, we can now schedule this action to the crontab too. Start the
crontab editor again:
EDITOR=nano crontab -e
We will now alter our backup line: we want to add info to copy our
backup archive when it’s created. So, we append the new command so
that it looks like this:
30 3 * * * /bin/tar -czf /backup/wordpress/wordpress-`date +%m%d%y`.tar.gz /var/www/wordpress;/usr/bin/scp -i /root/.ssh/id_rsa_backup /backup/wordpress/wordpress-`date +%m%d%y`.tar.gz firstname.lastname@example.org:/home/backup/backups
Note: this is not the usual way to do it, it would be better to setup
a script which does all the tasks and then schedule the script. But
for the brevity of this article, we’ll use that form.
Incremental Backup #
But what if we have our own backup software at another server? We just
want to synchronize the data over, and then leave the other server to
do the backup work. In addition, we want to preserve file stamps. Then
we use rsync. The use case here is that we want to
just incrementally copy over everything from
/var/www/wordpress to a remote server, this time to a
/home/backup/snapshots/wordpress directory. Here is a simple
command to do all that:
ssh email@example.com "mkdir -p /home/backup/sync" rsync -avz --delete -e "ssh -i /root/.ssh/id_rsa_backup" /var/www/wordpress firstname.lastname@example.org:/home/backup/sync
The first line creates a snapshot directory and the second copies the
changed files over. That means the files that were modified,
newly created or deleted.
We can schedule it in cron too:
EDITOR=nano crontab -e
The crontab line should look like this:
30 3 * * * /usr/bin/rsync -avz --delete -e "ssh -i /root/.ssh/id_rsa_backup" /var/www/wordpress email@example.com:/home/backup/sync
Now our remote server will always have a fresh synced copy of the
data, and we can do the backup there.
Backup Database #
We can also backup our database. First, we want to dump the data. If
we followed the wordpress install guide, we also have a database
wordpress, accessed by user wordpressuser with
password password. We can do the initial dump like this:
mkdir /backup/mysql mysqldump /backup/mysql/initial.sql.gz
This command created a initial.sql.gz gziped SQL file.
To do it on a daily basis, we can schedule it in cron, like before.
Our resulting cron line should look like this:
0 4 * * * /usr/bin/mysqldump /backup/mysql/mysql--`date +%m%d%y`.sql.gz
Now we could also combine it with scp or rsync to copy it remotely.
0 4 * * * /usr/bin/mysqldump /backup/mysql/mysql-`date +%m%d%y`.sql.gz; /usr/bin/scp -i /root/.ssh/id_rsa_backup /backup/mysql/mysql-`date +%m%d%y`.sql.gz firstname.lastname@example.org:/home/backup/
With this setup, we have a basic backup of our data set up for a case