Backup Script
I have multiple local servers and machines I want to backup to one central location. The criteria are that it has to be encrypted, both when transferring and storing, automatic and transparent, and redundant.
Previous Routines
A few years ago I found a great way to backup my servers to one central backup server using rsync and ssh. The backup server was located 100 meters away from the location with the servers, connected via wireless lan.
Every server was set up to use keys to login to the backup server without a password, making the process transparent. The rsync process was done over encrypted ssh, making it secure when transferring.
This method worked great and every few problems cropped up, other than lack of free space on backup drives. Both ends (clients and server) had a simple bash script that initiated the mounting of the drives, setting up ssh, including/excludign files, and rsyncing them over. Crontab took care of the scheduling.
Backup Routine
The new routing will be based on the previous method but simplified and the disks will be encrypted using Truecrypt.
For redundancy I will be using two 250 GB external USB-powered 2.5-inch harddrives, mine are from made by Western Digital. Both drives are identical and allows me to take one for backup at home (1) while leaving the other at work (2) to backup the servers/desktops.
When I see fit, I can swap the one at home (1) with the one at work (2) (and vice versa) and rsync will take care of the discrepancies by doing a incremental update. The incremental update will find all the new and modified files since the last time it saw that drive (1) and only copy over those files, while at the same time I have a redundant backup of all the files on the other drive (2). The 'freshness' of the redundant files depends on how often I swap out the drives (probably once a week).
Another issue I had was to find a filesystem that allowed for Linux permissions to be stored while still be accessibly by Mac OS X and Windows. After trying to get ext2/ext3 and NTFS to work, I found that, weirdly, HFS+ would be the most compatible filesystem. It was the only fs to have proper read and write, large file, and attribute/permission support. I didn't want to store backups on tar-balls.
Tools
All the tools used are Open Source and distributed free.
- rsync
- Truecrypt
- truecrypt-install
- OpenSSH
- ssh-keyinstall
- netcat
- Debian Linux (etch)
Many of these tools have dependencies, but these are the majo components. Command-line/terminal will be heavily used to manage, and run this routine.
Encrypted Drive
For the backup server I choose the one that would be up and running the most, and the best secured (no Internet ssh logins allowed, etc).
The external hard drive was automatically recognized and the modules were loaded without a problem by the vanilla 2.6.18-4 Debian kernel. The drive came with one partition that was FAT32 formatted.
If the drive is not formatted, use fdisk to add a primary partition. It doesn't matter which filesystem the partition is formatted as it will be reformatted during the Truecrypt setup.
elitus kernel: usb 1-2: new full speed USB device using uhci_hcd and address 5 elitus kernel: usb 1-2: configuration #1 chosen from 1 choice elitus kernel: scsi3 : SCSI emulation for USB Mass Storage devices elitus kernel: usb-storage: device found at 5 elitus kernel: usb-storage: waiting for device to settle before scanning ~ elitus kernel: Vendor: WD Model: 2500BEV External Rev: 1.04 elitus kernel: Type: Direct-Access ANSI SCSI revision: 04 elitus kernel: SCSI device sdb: 488397168 512-byte hdwr sectors (250059 MB) elitus kernel: sdb: Write Protect is off elitus kernel: sdb: Mode Sense: 21 00 00 00 elitus kernel: sdb: assuming drive cache: write through elitus kernel: SCSI device sdb: 488397168 512-byte hdwr sectors (250059 MB) elitus kernel: sdb: Write Protect is off elitus kernel: sdb: Mode Sense: 21 00 00 00 elitus kernel: sdb: assuming drive cache: write through elitus kernel: sdb: sdb1 elitus kernel: sd 3:0:0:0: Attached scsi disk sdb elitus kernel: usb-storage: device scan complete
Unfortunately, this motherboard and chipset only support USB v1.1.
Truecrypt
As of writing, there are no package maintainer for Truecrypt and it has to be compiled from source. Fortunately, some one has put together a handy truescript-installer script package that automates major parts of the process. Most of the ground work for this part was done by jaalto over at debian-administration.org.
Prepare Kernel
Prepare by installing the kernel sources, headers and kbuild.
uname -a apt-cache search 'linux-source|linux-kbuild|linux-headers' # Find the matching ones KVER=$(uname -r | sed 's/-.*//') apt-get install linux-source-$KVER linux-kbuild-$KVER linux-headers-$KVER
Create the required kernel CPU architecture files by entering and exiting the kernel configuration menu.
cd /usr/src tar -jxf linux-source-$KVER*.bz2 cd /usr/src/linux-source-$KVER cp /boot/config-$KVER .config make menuconfig # Look at the bottom, select exit, and Yes when prompted to save the settings
Build Truecrypt
Now, to create the truecrypt binary, docs, and mobules, downloading and executing the truecrypt-installer package.
Go to http://debian.cante.net/truecrypt-installer and download the installer package compatible with the available Truecrypt version, as of writing truecrypt-installer_20071024-1_i386.deb for Truecrypt 4.3a.
wget http://cante.net/~jaalto/tmp/debian/truecrypt-installer/truecrypt-installer_20071024-1_i386.deb dpkg -i truecrypt-installer_20071024-1_i386.deb # Dependencies could be a problem, I had to install the following packages apt-get install bzr debhelper dpatch html2text python-celementtree python-central python-elementtree python-support
Execute truecrypt-download and if it can't find the truecrypt source code, download it manually.
truecrypt-download # Or cd /usr/src wget http://tldp.etf.bg.ac.yu/gentoo/distfiles/truecrypt-4.3a-source-code.tar.gz
Now begin the build process. If it stops mid-way, try to delete all the truecrypt* files and directories in /usr/src and start from the beginning. The script relies on online trunk files to be available, which could pose a problem in the future.
truecrypt-build
If the process successfully finishes, install the resulting packages.
dpkg -i /usr/src/truecrypt-{cli,doc,modules-linux,modules-modprobe}*.deb
The install script will add the truecrypt module to /etc/modules so that it loads on boot.
Encrypting Drive
There is only one main binary called truecrypt. The easiest way to setup a new drive is to follow the simple guide.
truecrypt --quick --create /dev/sdb1 Volume type: 1) Normal 2) Hidden Select [1]: 1 WARNING: Data on device will be lost. Continue? [y/N]: y Filesystem: 1) FAT 2) None Select [1]: 1
Hash algorithm: 1) RIPEMD-160 2) SHA-1 3) Whirlpool Select [1]: 1
Encryption algorithm: 1) AES 2) Blowfish 3) CAST5 4) Serpent 5) Triple DES 6) Twofish 7) AES-Twofish 8) AES-Twofish-Serpent 9) Serpent-AES 10) Serpent-Twofish-AES 11) Twofish-Serpent Select [1]: 1 Enter password for new volume '/dev/sdb1': Re-enter password: Enter keyfile path [none]: TrueCrypt will now collect random data. Please type at least 320 randomly chosen characters and then press Enter: 4qGSW(&/CXU... Done: 0.00 MB Speed: 0.00 MB/s Left: 45222:49:57
I choose not to use keyfiles as I'd experiences some problems with them earlier, might work later though. The quick option finishes the format at the end in under a minute. I don't want to hang around waiting for the drive to format when I'm going to reformat it later, but I still understand that truecrypt normally randomizes the sectors while formatting the drive making it less prone to obscurity attacks.
