Q. Is There a UNIX / Linux unerase or undelete command? How do I undelete files under a UNIX / Linux system?
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.
Q. One of my responsibilities is backing up UNIX server. How do I backup data under HP-UX UNIX? How do I use mt, fbackup and frecover commands to perform full and incremental backups?
Q. How can I copy one hard disk to another using dd command?
A. dd command can copy disk in raw format. It will copy partition table and bootloader and all partitions within this disk. For example, you can copy /dev/sda to /dev/sdb (same size) using the following dd command. dd should complete with no errors, but output the number of records read and written.
Login as the root user (use sudo or su command)
Open terminal or shell prompt and type the following dd command:
# dd if=/dev/sda of=/dev/sdb
- if=/dev/sda : Input disk (source)
- of=/dev/sdb : Output disk (destination)
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 firstname.lastname@example.org:/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 email@example.com:/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 firstname.lastname@example.org:.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
rsync --exclude '*.cpp' --exclude '*.log' -avz -e ssh email@example.com:/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:
Save and close the file.
Q. How do I backup files and database for the Red Hat Enterprise Linux / CentOS Linux? Currently I’ve MySQL server running on CentOS 5 and Web server and file server using RHEL 5. How do I backup all these servers?
A. Regular backup is an essential for Linux system. You can take backup on
=> NAS Server
=> Network server etc
Implementing a backup policy that includes rotating backup media and keeping copies of backup media offsite is the most reliable way of minimizing damage. See following resources on our site for more information including commands and shell scripts: