Table of Contents
Everyone has personal data that nothing could recreate (pictures, emails, creations, …), or global data and configuration that it would take a lot of time to recreate. However you can lose some of them or all of them in several situations: hard drive crash, hard drive corruption, computer theft, computer destruction (fire…).
- partition your hard drive to have a separate partition for system and data
- put important application data on the data partition (configuration, emails, …)
- do a full mirror backup of the data partition regularly (eg with rsync or a deduplicate software such as Attic) on an external hard drive or a network drive. Try to keep at least one copy somewhere else from your home (network drive, or one at home and one at work).
- take precautions to put the odds on your side in case of problem: make copies of your disks MBR (output of command p of fdisk), of your encrypted partitions headers, etc.
The goal is threefold:
- No one non-authorized can ever access to your data
- The trusted persons can only access to your data in some conditions (deceased, coma, …)
- You are alerted when your data is accessed by the trusted persons (in case the access was not legitimate)
- A service that gives your data to designated persons when they provide a death certificate for you (Wishbook, …)
- Cons: sending a fake document, does not work for coma, service needs to remain available
- A service that regularly checks that you are alive by requesting a connection with your private credentials, and gives your data when you fail to do it.
- Cons: there will be some delay between when you stop pinging and when your data becomes available, service needs to remain available (but it can be automatized, and you can host it yourself)
- Split the secret between several people (cf Shamir's secret, implemented for instance in ssss or libgfshare), so that X out of Y need to agree to obtain your data.
- Cons: people need to remain accessible (and not loose the information), compromise between robustness and risk of conspiracy
What to transmit?
- Passwords (master password of your password manager, computer, encrypted data partitions, phone, …)
- Instructions about what data you have
- Different levels of amount of information for your spouse, children, other family, friends?
- How to transmit data (such as pictures) to a child? Probably has to go through a tutor.
By default ext3 reserves 5% of disk space to super-user. The intent is to let to critical applications the ability to write to the disk when it is full, but it has no use for a data partition, you just waste 5% of your partition.
You can check and remove these reserved blocks with the following commands:
tune2fs -l /dev/sda1 | grep Reserved tune2fs -r 0 /dev/sda1
- geekie for images (fork of gqview)
- secure-delete (srm, sfill, sswap, smem)
- -l option to be a lot faster: 2 passes instead of 38 (or -ll for only 1 pass), enough to prevent the use of consumer tools like photorec, but not for specialized companies and governments
- shred (less advanced but more common)
First unmount your partition and remount it read-only.
extundelete –restore-file Documents/file.dat /dev/sda4: the easiest solution if there are only a few files and you know their name. Accepts not unmounting the partition, works generally ok if you do it immediately after removing the files.
testdisk(photorec) is great to recover files on a mobile storage device because it works with any filesystem (finds signatures in data so no need of journal), and find all deleted files on the partition.
ext3grep <partition> --restore-file <filename> # filename => file ; works great, but only for one file at a time... ext3grep <partition> --restore-all --deleted --after=1270639550 # dates -> files ext3grep <partition> --histogram=dtime --deleted --after=1270639000 --before=1270640000 # => dates ext3grep <partition> --ls --inode 2 # filenames => inodes (navigating in directories with inodes) ext3grep <partition> --search Libs/jafar/modules/ # filename,dates -> blocks ext3grep <partition> --restore-inode <inode> # inodes => files
Notes: “restore-all” failed while building stage2 cache with error “ext3grep: init_directories.cc:535: void init_directories(): Assertion `lost_plus_found_directory_iter != all_directories.end()' failed.”. However doing a “ls inode” created this stage2 cache, and afterwards “restore-all” worked… but just restored everything on the disk even not deleted files/dirs, not taking into account the “after” option… But manually editing the stage2 cache to only keep files/dirs you want to restore then “restore-all” worked perfectly!
In case the MBR/partition table of you disk is damaged.
Make a backup before
You should always keep a backup of your partition table !
The first way is to store the output of p command of
You can also do a dump of the MBR and EBR:
dd if=/dev/sda of=sda.dd bs=512 count=1 # full MBR dump sfdisk -d /dev/sda > sda.sfdisk # MBR and EBR partition tables
Out of curiosity, the
file command is able to interpret the content of your MBR dump:
Restore with a backup
If you have the output of the p command of
fdisk, then you can manually recreate the partition table with
fdisk with the same information. As long as you don't mount or format, modifying the partition table with
fdisk doesn't modify the partitions data.
If you have a full dump of MBR and EBR, you can automatically restore it:
dd if=sda.dd of=/dev/sda sfdisk /dev/sda < sda.sfdisk
To restore the MBR without the partition table:
dd if=sda.dd of=/dev/sda bs=446 count=1
To restore only the partition table:
dd if=sda.dd of=/dev/sda bs=1 skip=446 count=66
Restore without a backup
If you don't have a copy of your partition info, don't panic, some software can recover them by searching for the partitions in the disk content (but it has to be formatted as a standard filesystem, ie not encrypted):