An Automated Reliable Backup Solution
Once I had committed to building this backup solution, I had to decide which hardware components I was going to use. Given my functionality, reliability, performance and general requirements, I decided to build a RAID 1—mirrored—array-based network solution. This meant that I needed two hard drives and a RAID controller that would support at least two hard drives.
I started by looking at small form-factor motherboards that I might use. I had used Mini-ITX motherboards in a number of other projects and knew that there was close to full Linux support for it. Given that this project did not require a fast CPU, I decided on the EPIA Mini-ITX ML8000A motherboard, which has an 800MHz CPU, a 100Mb network interface and one 32-bit PCI slot built in to it. This met my motherboard, CPU and network interface requirements and provided a PCI slot for the RAID controller.
After deciding on the form factor and motherboard, I had to choose a case and power supply that would provide enough space to fit a PCI hardware RAID controller, the Mini-ITX motherboard and two full-size hard drives, while complying with my general requirements. I compared a large number of Mini-ITX cases. I found only one, the Silver Venus 668, that was flexible enough to support everything I needed. After choosing the motherboard and case, I looked at the RAM requirement, and I chose 512MB of DDR266 RAM. I had great difficulty finding US Mini-ITX distributors. Luckily, I found a company, Logic Supply, which provided me with the motherboard, case, power supply and RAM as a package deal for a total of $301.25 US, including shipping. At this point, I had all of the components except the RAID controller and hard drives.
Finding a satisfactory RAID controller was extremely difficult. Many RAID controllers actually do their processing in operating system-level drivers rather than on a chip in the RAID controller card itself. The 3ware 8006-2LP SATA RAID Controller is a two-drive SATA controller that does its processing on the controller card. I acquired the 3ware 8006-2LP from Monarch Computer Systems for a total of $127.83 US, including shipping.
At this point, I needed only the hard drives. I eventually decided on buying two 200GB Western Digital #2000JS SATA300 8MB Cache drives from Bytecom Systems, Inc., for a total of $176.69 US, including shipping. At this point, I had all of my hardware requirements satisfied. In the end, the hardware components for this system cost a total of $604.77 US—well below the approximate $1,000 US cost of the RAID array network appliances that failed to satisfy most of my requirements.
After building the computer, I decided to install Debian stable 3.1r2 on the newly built server's RAID array because of its superior package management system. I then installed an SSH dæmon so that the file server could be accessed securely. Once the SSH package was installed, I created a user account for myself on the file server. The user account home directory is where the backup data is stored, and all users who want to back up to the server will have their own accounts on the file server.
Once the file server was set up, I had to configure a computer to be backed up. Because Duplicity is integrated with GnuPG and SSH, I configured GnuPG and SSH to work unattended with Duplicity. I set up the following configuration on all the computers that I wanted to back up onto my newly created file server.
I installed Duplicity on a Debian Linux computer using apt-get with the following command as superuser:
# apt-get install duplicity
Once Duplicity was installed, I created a DSA key pair and set up SSH DSA key authentication to provide a means of using SSH without having to enter a password. Some people implement this by creating an SSH key without a password. This is extremely dangerous, because if people obtain the key, they instantly have the same access that the original key owner had. Using a password-protected key requires people who get the key also to have the key's password before they can gain access. To create an SSH key pair and set up SSH DSA key authentication, I ran the following command sequence on the client machine:
$ ssh-keygen -t dsa $ scp ~/.ssh/id_dsa.pub <username>@<server>: $ ssh <username>@<server> $ cat id_dsa.pub >> ~/.ssh/authorized_keys2 $ exit
The first command creates the DSA key pair. The second command copies the previously generated public key to the backup server. The third command starts a remote shell on the backup server. The fourth command appends the public key to the list of authorized keys, enabling key authentication between the client machine and the backup server. The fifth and final command exits the remote shell.
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- Embed Linux in Monitoring and Control Systems
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