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files backup

Q. How do I use rsync command to back up a home directory under Linux operating system?

A. rsync command easily backup your home directory to local secondary hard disk or remote server using ssh protocol. rsync is a software application for Unix systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate.

Task: Backup /home/tom to /mnt/usbpen

Assuming that USB pen or external USB hard disk is mounted at /mnt/usbpen, enter the following command to backup (sync) new files and changes to existing files but don't remove files in backup directory:
$ rsync -au /home/tom /mnt/usbpen
To delete files in backup directory that no longer exist in directory being backed up, enter:
$ rsync -au --delete /home/tom /mnt/usbpen

See our previous article about using rsync for transferring files under Linux or UNIX from local or remote network computer.

How to backup the remote files in Linux / UNIX

Q. How do I make remote backups under Linux? I’ve CentOS 5 Linux server located in remote data center and I’d like to backup it to local or another server?

A. Both Linux / UNIX come with handy tools to make secure remote backups. You can use tool called rsync for automating remote backups of your Linux, UNIX, Windows server, Mac OS X and BSD systems. rsync is a program with many more options and uses the rsync remote-update protocol to greatly speed up file transfers when the destination file is being updated.

Task: Copy files / backup files from remote Linux server

Let us say you would like to backup files from remote server called server.nixcraft.in and directory called /home/vivek to local directory called /backup, type the command as follows on local system:
$ rsync -avz -e ssh vivek@server.nixcraft.in:/home/vivek/ /backup
You need to supply password for vivek user.

Task: Exclude files from backup

You can also skip few files from backup. Let us say you don't want to backup all C source code file, enter:
$ rsync --exclude '*.cpp' -avz -e ssh vivek@server.nixcraft.in:/home/vivek/ /backup

Task: Automatic backup using a shell script

SSH always prompts for a password. To automate process via a shell script you need to remove password using SSH key i.e. generate passphraseless keys, enter (type at local system):
$ ssh-keygen -t dsa
When asked for to enter passphrase, just press [ENTER] key twice. Now copy public key to remote server:
$ scp ~/.ssh/id_dsa.pub vivek@server.nixcraft.in:.ssh/authorized_keys
Now you can login without a password. For more information see - howto setup SSH with DSA public key authentication and RSA key authentication for password less login.

Now create a simple shell script as follows:
$ vi backup.sh
Append code:
#!/bin/bash
rsync --exclude '*.cpp' --exclude '*.log' -avz -e ssh vivek@server.nixcraft.in:/home/vivek/ /backup

Setup executable permission using chmod command:
$ chmod +x backup.sh
Use cron to command to backup remote server:
$ crontab -e
Make a backup everyday:
@daily /path/to/backup.sh
Save and close the file.