It has been made clear that digital data is not safe. I once had a backup system, but the one time I needed a backup, my backup harddrive failed and I lost all my data.
At university, I learned about RAID systems, but they are too expensive and too cumbersome for my purposes. That's why I made my own little cheap backup system.
I understood that you need to save data in at least two different locations for them to be at least somewhat safe. I bought two external hard drives with which I built a makeshift RAID1 system. Here's what I did:
A filesystem
First things first. I plugged in my harddrives via USB, but they're not being mounted automatically, so need to locate them.
$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT ... sdc 8:48 0 931.5G 0 disk └─sdc1 8:49 0 931.5G 0 part sdd 8:64 0 931.5G 0 disk └─sdd1 8:65 0 931.5G 0 part
Oh, right, I'm going to need sudo rights for this. Let's just get those rights right now, so I don't have to type sudo everywhere.
$ sudo su
I don't like Windows' filesystems, but they're on most harddrives by default, so I'm wiping those off my drives.
$ wipefs --all /dev/sdc $ wipefs --all /dev/sdd
Now that I have two clean disks, I need to partition them again, and add a new filesystem. I'm just going to make two single-partition drives. There's no need here to add any more partitions.
$ fdisk /dev/sdc
...
$ fdisk /dev/sdd
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1):
First sector (2048-1953458175, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-1953458175, default 1953458175):
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Next, I need a fun file system. My friend recommended BTRFS, for multiple reasons.
It's open source (GPL).
It focusses on fault tolerance and repair.
Honestly, I just wanted to try something other than ext4 for a change.
$ mkfs.btrfs /dev/sdc
...
$ mkfs.btrfs /dev/sdd
Btrfs v3.17.1
See http://btrfs.wiki.kernel.org for more information.
Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
fs created label (null) on /dev/sdd
nodesize 16384 leafsize 16384 sectorsize 4096 size 931.48GiB
Finally, I could mount my system for the first time. I chose a spot in the root directory, but that doesn't really matter.
$ mkdir /backup $ mkdir /backup/hdd0 $ mkdir /backup/hdd1 $ mount /dev/sdc1 /backup/hdd0 $ mount /dev/sdd1 /backup/hdd1
There, now I have two identical empty 1TB harddrives.
At this point, it's very easy to use these as a backup system. I just write to the first disk, and copy everything over to the second with rsync.
rsync --recursive /backup/hdd0 /backup/hdd1I could have the drives mounted all the time, and put this command into a cronjob, but I don't use my backup system that much, so I just mount the drives whenever I'm making a backup, or restoring one.