Build a Home Terabyte Backup System Using Linux
During the past few years, I have built backup servers using Red Hat Linux 9, but you can use any flavor of Linux. I use Red Hat 9 because it is stable, free, currently maintained (Fedora Legacy Project) and simple to install and configure. If you buy a new computer, you may have to use a more current version of Linux. I generally do not use RAID for low-budget systems where cost is paramount, but it is worth considering.
Software requirements for a Linux backup server are minimal. Basic network administration utilities (including the secure shell, SSH, and secure shell daemon, sshd) and rsync are required. rsync is a fast, incremental duplication/synchronization utility that comes with most Linux distributions. With SSH and rsync, you can carry out virtually all basic backup tasks. It is advantageous for a backup server also to be a fileserver, so I install Samba, the SMB fileserver as well. I use Samba because it is the default fileserver for MS Windows clients, and it also is readily accessible by any UNIX system (including Mac OS X) using a Samba client. If you have a homogenous UNIX network, you can use NFS, which I will not discuss here.
If you need to attach additional disks to your server, begin by making sure you have enough data (IDE/SATA/SCSI) cables and power lines to accommodate the expansion. Ensure that your drive is Linux-compatible (although most are). Turn off the power to your computer and disconnect the power cable. Physically attach the disk(s) to your computer. Linux should recognize the new disk(s) on boot. If your drive is not recognized, your disk is incompatible or you need to locate and install a driver for it. Check boot messages for new drives using the dmesg command. The boot message for an IDE drive may look like this:
hdb: ST3400832A, ATA DISK drive
All IDE/ATA (and some SATA) drives have the designation hdx, where the x is replaced with a letter of the alphabet (b in this case). Similarly, adding new USB or SCSI (and some SATA) disks gives boot messages indicating a new drive designation sdx, where the x is replaced by the appropriate letter.
Most Linux distributions come with a GUI disk manager. These disk managers let you define and format partitions (I generally use one partition per backup disk), assign mountpoints (for example, /data1, /data2) and mount the partition. The process also can be done from the command line using fdisk to create partitions.
Creating New Partitions
To create new partitions on hdb (above), type:
Type m at the fdisk prompt for a help summary. Typing n at the prompt asks about the new partition we are creating:
Command action e extended p primary partition (1-4) p
For a single primary partition, type in p:
Partition number (1-4):1
You are then prompted for a partition number (type 1 for a single partition). Next, set the partition size by determining the first and last cylinder. Because we are using the whole disk, you should be able to select the default values (the first and last cylinders):
First cylinder (1-48641, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-48641, default 48641): Using default value 48641
Type w to write the partition table. You now have a partition, /dev/hdb1, that occupies the whole disk.
Next, format the partition in the filesystem of choice (mine is in the ext3 format) using the mkfs command:
mkfs -t ext3 /dev/hdb1
Create a mountpoint for the new partition of your new disk (I'll call it /data1):
Mount the newly created ext3 partition:
mount -t ext3 /dev/hdb1 /data1
And, test reading and writing. Finally, add a line in /etc/fstab, the mount table, to mount automatically during the boot process:
# Device mountpoint fstype options freq pass_no /dev/hdb1 /data1 ext3 defaults 1 2
rsync is included in most Linux distributions. You need rsync and SSH on both your backup client and server. Check to see whether rsync installed by typing rsync at the command prompt or check your list of installed packages. If you cannot find a binary distribution for your package, you can download the source code for rsync by following links on the rsync home page (see the on-line Resources).
The simplest way to run rsync over a network is as a standalone application using SSH for authentication. You can run rsync as a daemon with more features, but you won't need to in this case. I illustrate this here with a backup client named foo and a server named bar.
To replicate the directory /home on Linux machine foo with directory /data1/foo of backup server bar from client foo using rsync and SSH, type:
rsync -az /home -e ssh bob@bar:/data1/foo
You will be prompted for user bob's password, and then the foo /home directories are replicated to /data1/foo/home on bar (bob needs an account on the server and write permission for /data1/foo).
To avoid having to type bob's password each time, create a private/public key pair for SSH authentication without a password. This allows you to automate the login process.
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