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FAQ - Frequently Asked Questions

General

Does Back in Time support full system backups?

Back in Time is suited for file-based backups.

A full system backup is neither supported nor recommended (even though you could use Back in Time (root) and include your root folder \) because

  • Mounted file systems (even remote locations)
  • the backup needed to be done from within the running system
  • Linux kernel special files (eg. /proc) must be excluded
  • locked or open files (in an inconsistent state) must be handled
  • backups of additional disk partitions (bootloader, EFI...) are required to be able to boot
  • a restore cannot overwrite the running system (where the backups software is running) without the risk of crashes or losing data (for that a restore must be done from a separate boot device normally)
  • ...

For full system backups look for

  • a disk imaging ("cloning") solution (eg. Clonezilla)
  • file-based backup tools that are designed for this (eg. Timeshift)

Does Back in Time support backups on cloud storage like OneDrive or Google Drive?

Cloud storage as backup source or target is not support because Back in Time uses rsync as backend for file transfer and therefore a locally mounted file system or a ssh connection is required. Neither is supported by cloud storage.

Even with native support for mounting a cloud storage, most of the time it won't work because of limited support for 'special' file access which is used by BiT (eg. Linux hardlinks, atime).

Typically "locally mounted" cloud storage uses a web-based API (REST-API) which does not support rsync.

For a discussion about this topic see Backup on OneDrive or Google Drive.

Where is the log file?

There are three distinct logs generated:

  1. The snapshot log contains messages specific to a particular snapshot at a given time. It is stored within each snapshot and can be accessed through the GUI.

  2. The restore log contains messages specific to a particular restore process. It is displayed in the GUI after each restore. It is also located in the folder ~/.local/share/backintime/ and is named restore_.log for the main profile, restore_2.log for the second, and so forth.

  3. The application log is generated using the syslog feature of the operating system. See How to read log entries? for further details.

How to read log entries?

Both the snapshot and restore log files are plain text files and can be read accordingly. Refer to Where is the log file?. The application log is generated via syslog using the identifier backintime. Depending on the version of Back In time and the GNU/Linux distribution used, there are three ways to get the log entries.

  1. On modern systems:

    journalctl --identifier backintime

  2. With an older Back In Time version (1.4.2 or older):

    journalctl --grep backintime

  3. If the error message journalctl: command not found appears, directly examine the syslog files:

    sudo grep backintime /var/log/syslog

How to move snapshots to a new hard-drive?

There are three different solutions:

  1. clone the drive with dd and enlarge the partition on the new drive to use all space. This will destroy all data on the destination drive!

     sudo dd if=/dev/sdbX of=/dev/sdcX bs=4M

    where /dev/sdbX is the partition on the source drive and /dev/sdcX is the destination drive

    Finally use gparted to resize the partition. Take a look at the Ubuntu Docu for more info on that.

  2. copy all files using rsync -H

     rsync -avhH --info=progress2 /SOURCE /DESTINATION

  3. copy all files using tar

    cd /SOURCE; tar cf - * | tar -C /DESTINATION/ -xf -

Make sure that your /DESTINATION contains a folder named backintime, which contains all the snapshots. BiT expects this folder, and needs it to import existing snapshots.

How to move a large directory in the backup source without duplicating the files in the backup?

If you move a file/folder in the source ("include") location that is backed-up by BiT it will treat this like a new file/folder and create a new backup file for it (not hard-linked to the old one). With large directories this can fill up your backup drive quite fast.

You can avoid this by moving the file/folder in the last snapshot too:

  1. Create a new snapshot

  2. Move the original folder

  3. Manually move the same folder inside BiTs last snapshot in the same way you did with the original folder

  4. Create a new snapshot

  5. Remove the next to last snapshot (the one where you moved the folder manually) to avoid problems with permissions when you try to restore from that snapshot

Backups (snapshots)

Does Back In Time create incremental or full backups?

Back In Time does use rsync and its --hard-links feature. Because of that each snapshot is technically a full backup (contains each file) but copies only the really changed files (to save disk space) and "reuses" unchanged files by setting a so-called "hard-link".

In technical terms it is not an incremental backups.

How do snapshots with hard-links work?

From the answer on Launchpad to the question Does auto remove smart mode merge incremental backups?

If you create a new file on a Linux filesystem (e.g. ext3) the data will have a unique number that is called inode. The path of the file is a link to this inode (there is a database which stores which file point to which inode). Also every inode has a counter for how many links point to this inode. After you created a new file the counter is 1.

Now you make a new hardlink. The filesystem now just has to store the new path pointing to the existing inode into the database and increase the counter of our inode by 1.

If you remove a file than only the link from the path to that inode is removed and the counter is decreased by 1. If you have removed all links to that inode so the counter is zero the filesystem knows that it can override that block next time you save a new file.

First time you create a new backup with BIT all files will have an inode counter = 1.

snapshot0

path inode counter
fileA 1 1
fileB 2 1
fileC 3 1

Lets say you now change fileB, delete fileC and have a new fileD. BIT first makes hardlinks of all files. rsync than delete all hardlinks of files that has changed and copy the new files.

snapshot0

path inode counter
fileA 1 2
fileB 2 1
fileC 3 1

snapshot1

path inode counter
fileA 1 2
fileB 4 1
fileD 5 1

Now change fileB again and make a new snapshot

snapshot0

path inode counter
fileA 1 3
fileB 2 1
fileC 3 1

snapshot1

path inode counter
fileA 1 3
fileB 4 1
fileC 5 2

snapshot2

path inode counter
fileA 1 3
fileB 6 1
fileD 5 2

Finally smart-remove is going to remove snapshot0. All that is done by smart-remove is to rm -rf (force delete everything) the whole directory of snapshot0.

snapshot0 (no longer exist)

path inode counter
(empty) 1 2
(empty) 2 0
(empty) 3 0

snapshot1

path inode counter
fileA 1 2
fileB 4 1
fileD 5 2

snapshot2

path inode counter
fileA 1 2
fileB 6 1
fileD 5 2

fileA is still untouched, fileB is still available in two different versions and fileC is gone for good. The blocks on your hdd that stored the data for inode 2 and 3 can now get overridden.

I hope this will shed a light on the "magic" behind BIT. If it's even more confusing don't hesitate to ask ;)

How can I check if my snapshots are using hard-links?

Please compare the inodes of a file that definitely didn't change between two snapshots. For this open two Terminals and cd into both snapshot folder. ls -lai will print a list where the first column is the inode which should be equal for the same file in both snapshots if the file didn't change and the snapshots are incremental. The third column is a counter (if the file is no directory) on how many hard-links exist for this inode. It should be >1. So if you took e.g. 3 snapshots it should be 3.

Don't be confused on the size of each snapshot. If you right click on preferences for a snapshot in a file manager and look for its size, it will look like they are all full snapshots (not incremental). But that's not (necessary) the case.

To get the correct size of each snapshot with respect on the hard-links you can run:

du -chd0 /media/<USER>/backintime/<HOST>/<USER>/1/*

Compare with option -l to count hardlinks multiple times:

du -chld0 /media/<USER>/backintime/<HOST>/<USER>/1/*

(ncdu isn't installed by default so I won't recommend using it)

How to use checksum to find corrupt files periodically?

Starting with BIT Version 1.0.28 there is a new command line option --checksum which will do the same as Use checksum to detect changes in Options. It will calculate checksums for both the source and the last snapshots files and will only use this checksum to decide whether a file has changed or not. The normal mode (without checksums) is to compare modification times and sizes of the files which is much faster to detect changed files.

Because this takes ages, you may want to use this only on Sundays or only the first Sunday per month. Please deactivate the schedule for your profile in that case. Then run crontab -e

For daily snapshots on 2AM and --checksum every Sunday add:

# min hour day month dayOfWeek command
0 2 * * 1-6 nice -n 19 ionice -c2 -n7 /usr/bin/backintime --backup-job >/dev/null 2>&1
0 2 * * Sun nice -n 19 ionice -c2 -n7 /usr/bin/backintime --checksum --backup-job >/dev/null 2>&1

For --checksum only at first Sunday per month add:

# min hour day month dayOfWeek command
0 2 * * 1-6 nice -n 19 ionice -c2 -n7 /usr/bin/backintime --backup-job >/dev/null 2>&1
0 2 * * Sun [ "$(date '+\%d')" -gt 7 ] && nice -n 19 ionice -c2 -n7 /usr/bin/backintime --backup-job >/dev/null 2>&1
0 2 * * Sun [ "$(date '+\%d')" -le 7 ] && nice -n 19 ionice -c2 -n7 /usr/bin/backintime --checksum --backup-job >/dev/null 2>&1

Press CTRL + O to save and CTRL + X to exit (if you editor is nano. Maybe different depending on your default text editor).

What is the meaning of the leading 11 characters (e.g. "cf...p.....") in my snapshot logs?

This are from rsync and indicating what changed and why. Please see the section --itemize-changes in the manpage of rsync. See also some rephrased explanations on Stack Overflow.

Snapshot "WITH ERRORS": [E] 'rsync' ended with exit code 23: See 'man rsync' for more details

BiT Version 1.4.0 (2023-09-14) introduced the evaluation of rsync exit codes for better error recognition:

Before this release rsync exit codes were ignored and only the snapshot files parsed for errors (which does not find each error, eg. dead symbolic links logged as symlink has no referent).

This "exit code 23" message may occur at the end of snapshot logs and BiT logs when rsync was not able to transfer some (or even all) files See this comment in issue 1587 for a list all known reasons for rsync's exit code 23.

Currently you can ignore this error after checking the full snapshot log which error is hidden behind "exit code 23" (and possibly fix it - eg. delete or update dead symbolic links).

We plan to implement an improved handling of exit code 23 in the future (presumably by introducing warnings into the snapshot log).

What happens when I remove a snapshot?

Each snapshot is stored in a dated subdirectory of the "full snapshot path" shown in Settings. It contains a backup directory of all the files as well as a log of the snapshot's creation and some other details. Removing the snapshot removes this whole directory. Each snapshot is independent of the others, so other snapshots are not affected. However, the data of identical files is not stored redundantly by multiple snapshots, so removing a snapshot will only recover the space used by files that are unique to that snapshot.

Restore

After Restore I have duplicates with extension ".backup.20131121"

This is because Backup files on restore in Options was enabled. This is the default setting to prevent overriding files on restore.

If you don't need them any more you can delete those files. Open a terminal and run:

find /path/to/files -regextype posix-basic -regex ".*\.backup\.[[:digit:]]\{8\}"

Check if this correctly listed all those files you want to delete and than run:

find /path/to/files -regextype posix-basic -regex ".*\.backup\.[[:digit:]]\{8\}" -delete

Back In Time doesn't find my old Snapshots on my new Computer

Back In Time prior to version 1.1.0 had an option called Auto Host/User/Profile ID (hidden under General > Advanced) which will always use the current host- and username for the full snapshot path. When (re-)installing your computer you probably chose a different host name or username than on your old machine. With Auto Host/User/Profile ID activated Back In Time now try to find your Snapshots under the new host- and username underneath the /path/to/backintime/ path.

The Auto Host/User/Profile ID option is gone in version 1.1.0 and above. It was totally confusing and didn't add any good.

You have three options to fix this:

  • Disable Auto Host/User/Profile ID and change Host and User to match your old machine.

  • Rename the Snapshot path /path/to/backintime/OLDHOSTNAME/OLDUSERNAME/profile_id to match your new host- and username.

  • Upgrade to a more recent version of Back In Time (1.1.0 or above). The Auto Host/User/Profile ID option is gone and it also comes with an assistant to restore the config from an old Snapshot on first start.

Schedule

How does the 'Repeatedly (anacron)' schedule work?

In fact Back In Time doesn't use anacron anymore. It was to inflexible. But that schedule mimics anacron.

BIT will create a crontab entry which will start backintime --backup-job every 15min (or once an hour if the schedule is set to weeks). With the --backup-job command, BIT will check if the profile is supposed to be run this time or exit immediately. For this it will read the time of the last successful run from ~/.local/share/backintime/anacron/ID_PROFILENAME. If this is older than the configured time, it will continue creating a snapshot.

If the snapshot was successful without errors, BIT will write the current time into ~/.local/share/backintime/anacron/ID_PROFILENAME (even if Repeatedly (anacron) isn't chosen). So, if there was an error, BIT will try again at the next quarter hour.

backintime --backup will always create a new snapshot. No matter how many time elapsed since last successful snapshot.

Will a scheduled snapshot run as soon as the computer is back on?

Depends on which schedule you choose:

  • the schedule Repeatedly (anacron) will use an anacron-like code. So if your computer is back on it will start the job if the given time is gone till last snapshot.

  • with When drive get connected (udev) Back In Time will start a snapshot as soon as you connect your drive ;-)

  • old fashion schedules like Every Day will use cron. This will only start a new snapshot at the given time. If your computer is off, no snapshot will be created.

If I edit my crontab and add additional entries, will that be a problem for BIT as long as I don't touch its entries? What does it look for in the crontab to find its own entries?

You can add your own crontab entries as you like. Back In Time will not touch them. It will identify its own entries by the comment line #Back In Time system entry, this will be edited by the gui: and the following command. You should not remove/change that line. If there are no automatic schedules defined Back In Time will add an extra comment line #Please don't delete these two lines, or all custom backintime entries are going to be deleted next time you call the gui options! which will prevent Back In Time to remove user defined schedules.

Problems, Errors & Solutions

WARNING: A backup is already running

Back In Time uses signal files like worker<PID>.lock to avoid starting the same backup twice. Normally it is deleted as soon as the backup finishes. In some case something went wrong so that Back In Time was forcefully stopped without having the chance to delete this signal file.

Since Back In Time does only start a new backup job (for the same profile) if the signal file does not exist, such a file need to be deleted first. But before this is done manually, it must be ensured that Back In Time really is not running anymore. It can be ensured via

ps aux | grep -i backintime

If the output shows a running instance of Back In Time it must be waited until it finishes or killed via kill <process id>.

For more details see the developer documentation: Usage of control files (locks, flocks, logs and others)

Back in Time does not start and shows: The application is already running! (pid: 1234567)

This message occurs when Back In Time is either already running or did not finish regularly (e.g. due to a crash) and wasn't able to delete its application lock file.

Before deleting that file manually make sure no backintime process is running via ps aux | grep -i backintime. Otherwise, kill the process. After that look into the folder ~/.local/share/backintime for the file app.lock.pid and delete it.

For more details see the developer documentation: Usage of control files (locks, flocks, logs and others)

Switching to dark or light mode in the desktop environment is ignored by BIT

After restart Back In Time it should adapt to the desktops current used color theme.

It happens because Qt does not detect theme modifications out of the box. Workarounds are known, but generate a relatively large amount of code and in our opinion are not worth the effort.

Ubuntu - Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8))

In newer Ubuntu-based distros you may get this warning if you install Back In Time from PPA. The reason is that public keys of signed packages shall be stored in a new folder now (for details see https://itsfoss.com/apt-key-deprecated/).

A solution is described in #1338

Segmentation fault on Exit

This problem existed at least since version 1.2.1, and will hopefully be fixed with version 1.5.0. For all affected versions, it does not impact the functionality of Back In Time or jeopardize backup integrity. It can be safely ignored.

See also:

Version >= 1.2.0 works very slow / Unchanged files are backed up

After updating to >= 1.2.0, BiT does a (nearly) full backup because file permissions are handled differently. Before 1.2.0 all destination file permissions were set to -rw-r--r--. In 1.2.0 rsync is executed with --perms option which tells rsync to preserve the source file permission. That's why so many files seem to be changed.

If you don't like the new behavior, you can use "Expert Options" -> "Paste additional options to rsync" to add the value --no-perms --no-group --no-owner in that field.

What happens if I hibernate the computer while a backup is running?

Back In Time will inhibit automatic suspend/hibernate while a snapshot/restore is running. If you manually force hibernate this will freeze the current process. It will continue as soon as you wake up the system again.

What happens if I power down the computer while a backup is running, or if a power outage happens?

This will kill the current process. The new snapshot will stay in new_snapshot folder. Depending on which state the process was while killing the next scheduled snapshot can continue the leftover new_snapshot or it will remove it first and start a new one.

What happens if there is not enough disk space for the current backup?

Back In Time will try to create a new snapshot but rsync will fail when there is not enough space. Depending on Continue on errors setting the failed snapshot will be kept and marked With Errors or it will be removed. By default, Back In Time will finally remove the oldest snapshots until there is more than 1 GiB free space again.

NTFS Compatibility

Although devices formatted with the NTFS file system can generally be used with Back In Time, there are some limitations to be aware of.

NTFS File systems do not support the following characters in filenames or directories:

< (less than)
> (greater than)
: (colon)
" (double quote)
/ (forward slash)
\ (backslash)
| (vertical bar or pipe)
? (question mark)
* (asterisk)

If Back In Time tries to copy files where the filename contains those character, an "Invalid argument (22)" error message will be displayed.

It is recommended that only devices formatted with Unix style file systems (such as ext4) be used.

For more information, refer to this Microsoft page.

user-callback and other PlugIns

How to backup Debian/Ubuntu Package selection?

There is a user-callback example which will backup all package selections, sources and repository keys which are necessary to reinstall exactly the same packages again. It will even backup whether a package was installed manually or automatically because of dependencies.

Download the script, copy it to ~/.config/backintime/user-callback and make it executable with chmod 755 ~/.config/backintime/user-callback

It will run every time a new snapshot is taken. Make sure to include ~/.apt-backup.

How to restore Debian/Ubuntu Package selection?

If you made snapshots including apt-get package selection as described in the FAQ "How to backup Debian/Ubuntu Package selection?_" you can easily restore your system after a disaster/on a new machine.

  1. install Debian/Ubuntu on your new hard drive as usual

  2. install backintime-qt4 from our PPA

     sudo add-apt-repository ppa:bit-team/stable
 sudo apt-get update
 sudo apt-get install backintime-qt4

  3. connect your external drive with the snapshots

  4. Start Back In Time. It will ask you if you want to restore your config. Sure you want! Back In Time should find your snapshots automatically. Just select the one from which you want to restore the config and click Ok.

  5. restore your home

  6. recreate your /etc/apt/sources.list if you had something special in there. If your Debian/Ubuntu version changed don't just copy them from ~/.apt-backup/sources.list

  7. copy your repositories with

     sudo cp ~/.apt-backup/sources.list.d/* /etc/apt/sources.list.d/

  8. restore apt-keys for your PPAs with

     sudo apt-key add ~/.apt-backup/repo.keys

  9. install and update dselect with

     sudo apt-get install dselect
 sudo dselect update install

  10. Make some housecleaning in ~/.apt-backup/package.list. For example, you don't want to install the old kernel again. So run

     sed -e "/^linux-\(image\|headers\)/d" -i ~/.apt-backup/package.list

  11. install your old packages again with

     sudo apt-get update
 sudo dpkg --set-selections < ~/.apt-backup/package.list
 sudo apt-get dselect-upgrade

  12. If you used the new script which uses apt-mark to backup package selection proceed with next step. (there should be files ~/.apt-backup/pkg_auto.list and ~/.apt-backup /pkg_manual.list). Otherwise, you can stop here. Restore package selection with

     sudo apt-mark auto $(cat ~/.apt-backup/pkg_auto.list)
 sudo apt-mark manual $(cat ~/.apt-backup/pkg_manual.list)

Hardware-specific Setup

How to use QNAP QTS NAS with BIT over SSH

To use BackInTime over SSH with a QNAP NAS there is still some work to be done in the terminal.

WARNING: DON'T use the changes for sh suggested in man backintime. This will damage the QNAP admin account (and even more). Changing sh for another user doesn't make sense either because SSH only works with the QNAP admin account!

Please test this Tutorial and give some feedback!

  1. Activate the SSH prefix: PATH=/opt/bin:/opt/sbin:\$PATH in Expert Options

  2. Use admin (default QNAP admin) as remote user. Only this user can connect through SSH. Also activate on the QNAP SFTP on the SSH settings page.

  3. Path should be something like /share/Public/

  4. Create the public/private key pair for the password-less login with the user you use for BackInTime and copy the public key to the NAS.

    ssh-keygen -t rsa
ssh-copy-id -i ~/.ssh/id_rsa.pub  <REMOTE_USER>@<HOST>

To fix the message about not supported find PATH -type f -exec you need to install Entware-ng. QNAPs QTS is based on Linux but some of its packages have limited functionalities. And so do some of the necessary ones for BackInTime.

Please follow this install instruction to install Entware-ng on your QNAP NAS.

Because there is no web interface yet for Entware-ng, you must configure it by SSH on the NAS.

Some Packages will be installed by default for example findutils.

Login on the NAS and updated the Database and Packages of Entware-ng with

ssh <REMOTE_USER>@<HOST>
opkg update
opkg upgrade

Finally install the current packages of bash, coreutils and rsync

opkg install bash coreutils rsync

Now the error message should be gone and you should be able to take a first snapshot with BackInTime.

BackInTime changes permissions on the backup path. The owner of the backup has read permission, other users have no access.

This way can change with newer versions of BackInTime or QNAPs QTS!

How to use Synology DSM 5 with BIT over SSH

Issue

BackInTime cannot use Synology DSM 5 directly because the SSH connection to the NAS refers to a different root file system than SFTP does. With SSH you access the real root, with SFTP you access a fake root (/volume1)

Solution

Mount /volume1/backups to /volume1/volume1/backups

Suggestion

DSM 5 isn't really up to date any more and might be a security risk. It is strongly advised to upgrade to DSM 6! Also the setup with DSM 6 is much easier!

  1. Make a new volume named volume1 (should already exist, else create it)

  2. Enable User Home Service (Control Panel / User)

  3. Make a new share named backups on volume1

  4. Make a new share named volume1 on volume1 (It must be the same name)

  5. Make a new user named backup

  6. Give to user backup rights Read/Write to share backups and volume1 and also permission for FTP

  7. Enable SSH (Control Panel / Terminal & SNMP / Terminal)

  8. Enable SFTP (Control Panel / File Service / FTP / SFTP)

  9. Enable rsync service (Control Panel / File Service / rsync)

  10. Since DSM 5.1: Enable Backup Service (Backup & Replication / Backup Service) (This seems not to be available/required anymore with DSM 6!)

  11. Log on as root by SSH

  12. Modify the shell of user backup. Set it to /bin/sh (vi /etc/passwd then navigate to the line that begins with backup, press :kbd:I to enter Insert Mode, replace /sbin/nologin with /bin/sh, then finally save and exit by pressing :kbd:ESC and type :wq followed by :kbd:Enter) This step might have to be repeated after a major update of the Synology DSM! Note: This is quite a dirty hack! It is suggested to upgrade to DSM 6 which doesn't need this any more!

  13. Make a new directory /volume1/volume1/backups

    mkdir /volume1/volume1/backups

  14. Mount /volume1/backups on /volume1/volume1/backups

    mount -o bind /volume1/backups /volume1/volume1/backups

  15. To auto-mount it make a script /usr/syno/etc/rc.d/S99zzMountBind.sh

    #!/bin/sh

 start()
 {
        /bin/mount -o bind /volume1/backups /volume1/volume1/backups
 }

 stop()
 {
        /bin/umount /volume1/volume1/backups
 }

 case "$1" in
        start) start ;;
        stop) stop ;;
        *) ;;
 esac

    Note: If the folder /usr/syno/etc/rc.d doesn't exist, check if /usr/local/etc/rc.d/ exists. If so, put it there. (After I updated to Synology DSM 6.0beta, the first one did not exist anymore). Make sure the execution flag of the file is checked , else it will not get run at start! To make it executable, run: chmod +x /usr/local/etc/rc.d/S99zzMountBind.sh

  16. On the workstation on which you try to use BIT make SSH keys for user backup, send the public key to the NAS

    ssh-keygen -t rsa -f ~/.ssh/backup_id_rsa
ssh-add ~/.ssh/backup_id_rsa
ssh-copy-id -i ~/.ssh/backup_id_rsa.pub backup@<synology-ip>
ssh backup@<synology-ip>

  17. You might get the following error:

    /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: WARNING: All keys were skipped because they already exist on the remote system.

  18. If so, copy the public key manually to the NAS as root with

    scp ~/.ssh/id_rsa.pub backup@<synology-ip>:/var/services/homes/backup/
ssh backup@<synology-ip> cat /var/services/homes/backup/id_rsa.pub >> /var/services/homes/backup/.ssh/authorized_keys
# you'll still be asked for your password on these both commands
# after this you should be able to login password-less

  19. And proceed with the next step

  20. If you are still prompted for your password when running ssh backup@<synology-ip>, check the permissions of the file /var/services/homes/backup/.ssh/authorized_keys. It should be -rw-------. If this is not the case, run the command

    ssh backup@<synology-ip> chmod 600 /var/services/homes/backup/.ssh/authorized_keys

  21. Now you can use BackInTime to perform your backup to your NAS with the user backup.

How to use Synology DSM 6 with BIT over SSH

HowTo

  1. Enable User Home Service (Control Panel / User / Advanced). There is no need to create a volume since everything is stored in the home directory.

  2. Make a new user named backup (or use your existing account). Add this user to the user group Administrators. Without this, you will not be able to log in!

  3. Enable SSH (Control Panel / Terminal & SNMP / Terminal)

  4. Enable SFTP (Control Panel / File Service / FTP / SFTP)

  5. Since DSM 5.1: Enable Backup Service (Backup & Replication / Backup Service) (This seems not to be available/required anymore with DSM 6!) (Tests needed!)

  6. On DSM 6 you can edit the user-root-dir for sFTP: Control Panel -> File Services -> FTP -> General -> Advanced Settings -> Security Settings -> Change user root directories -> Select User Now select the user backup and Change root directory to User home

  7. On the workstation on which you try to use BIT make SSH keys for user backup, send the public key to the NAS

     ssh-keygen -t rsa -f ~/.ssh/backup_id_rsa
 ssh-add ~/.ssh/backup_id_rsa
 ssh-copy-id -i ~/.ssh/backup_id_rsa.pub backup@<synology-ip>
 ssh backup@<synology-ip>

  8. You might get the following error:

     /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
 /usr/bin/ssh-copy-id: WARNING: All keys were skipped because they already exist on the remote system.

  9. If so, copy the public key manually to the NAS as root with

     scp ~/.ssh/id_rsa.pub backup@<synology-ip>:/var/services/homes/backup/
 ssh backup@<synology-ip> cat /var/services/homes/backup/id_rsa.pub >> /var/services/homes/backup/.ssh/authorized_keys
 # you'll still be asked for your password on these both commands
 # after this you should be able to login password-less

  10. And proceed with the next step

  11. If you are still prompted for your password when running ssh backup@<synology-ip>, check the permissions of the file /var/services/homes/backup/.ssh/authorized_keys. It should be -rw-------. If this is not the case, run the command

    ssh backup@<synology-ip> chmod 600 /var/services/homes/backup/.ssh/authorized_keys

  12. In BackInTime settings dialog leave the Path field empty

  13. Now you can use BackInTime to perform your backup to your NAS with the user backup.

Using a non-standard port with a Synology NAS

If you want to use the Synology NAS with non-standard SSH/SFTP port (standard is 22), you have to change the Port on total 3 places:

  1. Control Panel > Terminal: Port = <PORT_NUMBER>

  2. Control Panel > FTP > SFTP: Port = <PORT_NUMBER>

  3. Backup & Replication > Backup Services > Network Backup Destination: SSH encryption port = <PORT_NUMBER>

Only if all 3 of them are set to the same port, BackInTime is able to establish the connection. As a test, one can run the command

rsync -rtDHh --checksum --links --no-p --no-g --no-o --info=progress2 --no-i-r --rsh="ssh -p <PORT_NUMBER> -o IdentityFile=/home/<USER>/.ssh/id_rsa" --dry-run --chmod=Du+wx /tmp/<AN_EXISTING_FOLDER> "<USER_ON_DISKSTATION>@<SERVER_IP>:/volume1/Backups/BackinTime"

in a terminal (on the client PC).

How to use Synology DSM 7 with BIT over SSH

HowTo

  1. Enable User Home Service (Control Panel > User & Group > Advanced).

  2. Make a new user named backup (or use your existing account) and add this user to the user group Administrators.

  3. Enable SSH (Control Panel > Terminal & SNMP > Terminal)

  4. Enable SFTP (Control Panel > File Services > FTP > SFTP)

  5. Enable rsync (Control Panel > File Services > rsync)

  6. Edit the user-root-directory for SFTP: Control Panel > File Services > FTP > General > Advanced Settings > Security Settings > Change user root directories > Select User > select the user backup > Edit and Change root directory to User home

  7. Make sure the 'homes' shared folder has the default permissions and that non-admin users and groups are not assigned Read or Write permissions on the 'homes' folder. The default permissions are described in this guide

  8. On the workstation on which you need to use BIT, make an SSH key pair for user backup, and send the public key to the NAS:

     ssh-keygen -t rsa -f ~/.ssh/backup_id_rsa
 ssh-copy-id -i ~/.ssh/backup_id_rsa.pub backup@<synology-ip>
 ssh backup@<synology-ip>

  9. Although not strictly necessary, Synology recommend setting the permissions for the .ssh directory and the authorized_keys file to 700, and 600 respectively:

    backup@NAS:~$ chmod 700 .ssh
backup@NAS:~$ chmod 600 .ssh/authorized_keys

  10. In BackInTime settings dialog leave the Path field empty

  11. Now you can use BackInTime to perform your backup to your NAS with the user backup.

Using a non-standard SSH port with a Synology NAS

If you want to use the Synology NAS with a non-standard SSH/SFTP port as advised by the Security Advisor package, you have to change the Port in 3 places (the default port number for all three is 22):

  1. Control Panel > Terminal & SNMP > Terminal: Port = <PORT_NUMBER>

  2. Control Panel > File Services > FTP > SFTP: Port number = <PORT_NUMBER>

  3. Control Panel > File Services > rsync > SSH encryption port = <PORT_NUMBER>

Only if all 3 are set to the same port is BackInTime able to establish the connection (don't forget to set the new port number in the BIT profiles).

To sign in with ssh using the new port number:

ssh -p PORT_NUMBER backup@<synology-ip>

or, for convenience you can edit or create ~/.ssh/config with the following:

Host <synology-ip>
    Port PORT_NUMBER

and then use just:

ssh backup@<synology-ip>

How to use Western Digital MyBook World Edition with BIT over ssh?

Device: WesternDigital MyBook World Edition (white light) version 01.02.14 (WD MBWE)

The BusyBox that is used by WD in MBWE for serving basic commands like cp (copy) doesn't support hardlinks. Which is a rudimentary function for BackInTime's way of creating incremental backups. As a work-around you can install Optware on the MBWE.

Before proceeding please make a backup of your MBWE. There is a significant chance to break your device and lose all your data. There is good documentation about Optware on http://mybookworld.wikidot.com/optware.

  1. You have to login to MBWE's web admin and change to Advanced Mode. Under System | Advanced you have to enable SSH Access. Now you can log in as root over ssh and install Optware (assuming <MBWE> is the address of your MyBook).

    Type in terminal:

     ssh root@<MBWE> #enter 'welc0me' for password (you should change this by typing 'passwd')
 wget http://mybookworld.wikidot.com/local--files/optware/setup-whitelight.sh
 sh setup-whitelight.sh
 echo 'export PATH=$PATH:/opt/bin:/opt/sbin' >> /root/.bashrc
 echo 'export PATH=/opt/bin:/opt/sbin:$PATH' >> /etc/profile
 echo 'PermitUserEnvironment yes' >> /etc/sshd_config
 /etc/init.d/S50sshd restart
 /opt/bin/ipkg install bash coreutils rsync nano
 exit

  2. Back in MBWE's web admin go to Users and add a new user (<REMOTE_USER> in this How-to) with Create User Private Share set to Yes.

    In terminal:

     ssh root@<MBWE>
 chown <REMOTE_USER> /shares/<REMOTE_USER>
 chmod 700 /shares/<REMOTE_USER>
 /opt/bin/nano /etc/passwd
 #change the line
 #<REMOTE_USER>:x:503:1000:Linux User,,,:/shares:/bin/sh
 #to
 #<REMOTE_USER>:x:503:1000:Linux User,,,:/shares/<REMOTE_USER>:/opt/bin/bash
 #save and exit by press CTRL+O and CTRL+X
 exit

  3. Next create the ssh-key for your local user. In the terminal

     ssh <REMOTE_USER>@<MBWE>
 mkdir .ssh
 chmod 700 .ssh
 echo 'PATH=/opt/bin:/opt/sbin:/usr/bin:/bin:/usr/sbin:/sbin' >> .ssh/environment
 exit
 ssh-keygen -t rsa #enter for default path
 ssh-add ~/.ssh/id_rsa
 scp ~/.ssh/id_rsa.pub <REMOTE_USER>@<MBWE>:./ #enter password from above
 ssh <REMOTE_USER>@<MBWE> #you will still have to enter your password
 cat id_rsa.pub >> .ssh/authorized_keys
 rm id_rsa.pub
 chmod 600 .ssh/*
 exit
 ssh <REMOTE_USER>@<MBWE> #this time you shouldn't been asked for password anymore
 exit

  4. You can test if everything is done by enter this

    ssh <REMOTE_USER>@<MBWE> cp --help

    The output should look like:

     Usage: cp [OPTION]... [-T] SOURCE DEST
 or: cp [OPTION]... SOURCE... DIRECTORY
 or: cp [OPTION]... -t DIRECTORY SOURCE...
 Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
 
 Mandatory arguments to long options are mandatory for short options too.
 -a, --archive same as -dR --preserve=all
     --backup[=CONTROL] make a backup of each existing destination file
 -b like --backup but does not accept an argument
     --copy-contents copy contents of special files when recursive
 ... (lot more lines with options)

    But if your output looks like below you are still using the BusyBox and will not be able to run backups with BackInTime over ssh:

     BusyBox v1.1.1 (2009.12.24-08:39+0000) multi-call binary
 
 Usage: cp [OPTION]... SOURCE DEST

Uncategorized questions

Which additional features on top of a GUI does BIT provide over a self-configured rsync backup? I saw that it saves the names for uids and gids, so I assume it can restore correctly even if the ids change. Great! :-) Are there additional benefits?

Actually it's the other way around ;) Back In Time stores the user and group name which will make it possible to restore permissions correctly even if UID/GID changed. Additionally it will store the current User -> UID and Group -> GID map so if the User/Group doesn't exist on the system during restore it will restore to the old UID/GID.

Hard to say which additional features Back In Time provides. You can script all of them in your own rsync script, too. But to name some features:

  • Inhibit suspend/hibernate during take snapshot
  • Shutdown system after finish
  • Auto- and Smart-Removal
  • Plugin- and user-callback support

Support for specific package formats (deb, rpm, Flatpack, AppImage, Snaps, PPA, …)

We assist and support other projects providing specific distribution packages. Thus, we suggest creating your own repository to manage and maintain such packages. It will be mentioned in our documentation as an alternative source for installation.

We do not directly support third-party distribution channels associated with specific GNU/Linux distributions, unofficial repositories (e.g. Arch AUR, Launchpad PPA) or FlatPack & Co. One reasons is our lack of resources and the need to prioritize tasks. Another reasons is that their are distro maintainers with much more experience and skills in packaging. We always recommend using the official repositories of GNU/Linux distributions and contacting their maintainers if Back In Time is unavailable or out dated.

Testing & Building

SSH related tests are skipped

They get skipped if no SSH server is available. Please see section Testing & Building about how to setup a SSH server on your system.

Setup SSH Server to run unit tests

Please see section Testing - SSH.