A Guide to Backing Up Your Home Directory Using rsync.
Guide Overview
The purpose of this guide is to show you how the rsync command can be used to backup your /home directory.
This guide is aimed at inexperienced users.
This guide is based on material found the official rsync home page:
References to other commands can be found on your systems' individual man pages:
man commandname
Introduction
The rsync command is typically used to transfer files through a network. However, when used in local mode it becomes a very powerful backup utility.
By default, all of your personal files and your program configuration files are in your "/home" directory. Each user has their own separate sub directory. They will appear as "/home/username1", "/home/username2", &c.
In most cases, recovering from a hard drive failure would involve reinstalling Linux on a new drive, recreating the user(s) name(s), and then restoring the "/home" directory from the backup.
Some Linux backup programs are based on rsync such as Time Vault, Flyback, and Grsync
In this guide we will look at the rsync command and it's practical use.
All commands are done in a Linux Terminal.
To enter Linux Terminal, from your desktop, press the following key combination simultaneously:
<ctl>+<alt>+t
To exit the Linux Terminal, simply enter the command exit.
Tools Needed
A working Linux system.
A backup media device.
For this the purpose of this guide, I am using 3.5" USB 3 SATA enclosure with a separate 12 volt power supply. It has a 2TB drive. My notebook has Xubuntu 20.04 installed on a 1TB drive.
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Part 
Using the basic rsync command:
If you are using Ubuntu, or one of its' derivatives, then rsync is installed by default.
To verify that you have rsync installed, simply enter the command “rsync” in the terminal, with no added switches or strings.
If rsync is installed, it will print it’s own help file to your screen.
If rsync is not installed, then you can use the following terminal commands to install it:
Debian or Ubuntu Based sudo apt install rsync
Red Hat, Fedora and CentOS yum install rsync
This is the rsync command in it's simplest form:
rsync -av /home/username /destination
Where:
rsync = basic command
-a = archive switch
-v = verbose switch
/home/username = source directory
/destination = target directory
The two basic switches are -a and -v.
The -a switch tells rsync to use archive mode. That is, rsync will preserve the original files names, but also ensures that symbolic links, devices, attributes, permissions, ownership, etc. are preserved in the transfer.
The -v switch tells rsync to be verbose. That is, it will display what it is doing on the screen. Otherwise you would just see a blank line on the screen, until the job was finished.
The directory /home/username, is the source. It can be an entire directory, or just a single file name.
The directory /destination, is the target where the source will be copied to.
It is important to note that there is a space between the source and the target.
In the above example, the entire "username" directory will be copied into the "destination" directory.
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What happens when we alter the source slightly. What if we use the command:
rsync -av /home/username/ /destination
Note the trailing slash after username.
By adding the trailing slash after username, we a telling rsync not to copy the directory of username, but rather only the contents of the directory.
The result would be that /destination/username would not be created, but rather all the files and sub directories would appear in /destination.
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If we use the command this way:
rsync -av /home/username/ /destination/some_other_name
The rsync command will create the /destination/some_other_name directory and transfer the contents of the /home/username directory to it.
You cannot multi tier the target. If you were to use /destination/target/some_other_name/ then the directory /destination/target must already exist.
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Part 
Practical use of rsync and more examples of how it works.
The program first examines the source and target, to see what is there. It will find out what files are already on the target, and what the difference, if any, there is between them and the same file on the source.
It will then transfer only the changed parts of any files that are already in the source, and the complete file for any new files.
Once the initial backup is done, then the incremental backups run very quickly, as only the changed data is sent to the source.
The time required to do a backup is dependent on the speed of your system, the amount of data, and the speed of the connection to the backup device.
I ran the following write speed test on my enclosure.
dd if=/dev/zero of=./speedTestFile bs=20M count=5 oflag=direct
5+0 records in
5+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.908418 s, 115 MB/s
I estimated the initial back up of my home directory, 372GB of data, to take about 55 minutes.
It actually took just over 58 minutes.
Subsequent backups take less than a minute. Somewhat longer, if I have downloaded new iso images.
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Removable Storage Devices
Removable storage devices should automatically mount it in the /media directory, under the users name.
The mounted device may appear as something like this:
/media/username/0cxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/
Sometimes there will be a string of numbers and letters appearing as the sub directory in the users media mount point.
That alpha numeric is the UUID number of the partition on the removable drive.
This typically occurs because when the media was formatted, it was not given a volume name.
In order to identify it to the user, Linux uses the UUID number of the partition.
To change this, and provide a more human readable volume name, you can use gparted or gnome-disks.
They both give you the ability to add or change a volume name. You can also use the command line.
Here are the commands to change partition labels:
e2lable /dev/sdxn
ntfslable /dev/sdxn
mlable /dev/sdxn
e2lable = ext2\3\4 native Linux file systems
ntfslable = Windows native ntfs file systems
mlable = DOS fat file systems
/dev/sdxn = The device, physical drive letter, and partition number
To obtain the physical drive letter and partition number of a removable drive, use the lsblk command, with the -f switch.
lsblk -f
This will print all of your block devices to your screen, showing their file system information.
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A typical rsync command for removable media would be:
rsync -av /home/username /media/username/backup_device/some_sub_directory
I have my backup device labelled BUD, with a directory called Backups. My command looks like this:
rsync -av /home /media/naught/BUD/Backups
This backs up all users to my external drive into the Backups directory.
A total system backup can be done with this command (All one line!):
sudo rsync -aAXv --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*",
"/media/*","/lost+found"} /* /media/naught/BUD/Backups
This would include virtually everything in the / Root partition.
The -A and -X switches preserve ownership and extended file attributes.
Notice that I used the --exclude= switch to omit certain directories.
Note the way they are listed between the { } parenthesizes.
Full path, enclosed in “ “ double quotation marks, with the /* trailing slash and wild card symbol, and separated by commas.
They are not essential to a system recovery. They would be recreated by the new system install.
As well as that, I omit my mount points, otherwise my server drive would be included. It has its own back up routine.
Also, if I tried to backup /media to /media/naught/BUD, then I would have created a loop.
For more advanced information on these, and other switches, see the rsync man page.
Use this command:
man rsync
Note: Use the letter q to exit from any man page.
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To back up to an NAS server on your home network, it must be mounted.
Although you can view and access a local NAS server using a file manager like Thunar, they normally don't mount the drive permanently.
To do that, you have to use the mount command, as super user.
The mount command would be similar to this:
sudo mount //some_networkshare/shared_name /mnt/a_mount_point
First, make the mount point in your file system. For example:
sudo mkdir /mnt/nas
sudo chown username:username -r /mnt/nas
Then mount the share. For example:
sudo mount //192.168.nnn.nnn/Share_Name /mnt/nas
The network share now appears as a regular directory in your file system.
The rsync command can be used to backup from or to that share.
When used in a network, you should add the -z switch to the rsync command.
It would look like this:
rsync -avz /home/username /mnt/nas/some_sub_directory
The -z switch tells rsync to use data compression when sending the files through the network. It does not actually compress the files at the other end. It compresses the data packets.
It is simply there to increase the speed of the transfer.
One of the best things about using rsync in conjunction with an NAS is that you can set it up as a cron job.
You can have it run every day, at ZeroDark30, to do a backup of your system.
For more advanced information, see the man pages for those commands.
man mkdir
man chown
man mount
man crontab
I suggest you read the documentation first, and encourage you to try it on your own. If you need help, post a question in the regular Linux Users forum.
In conclusion, if you want to take more personal control of your system, then you may want to start with rsync.
With older computers, using the command line in terminal reduces the overhead put on by GUI programs.
The more things you do from the terminal, the more you will realize how powerful Linux is as an operating system.
Cheers!
Naught 
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