Backups with rsnaphot to external USB drives

How long has it been since you last backed up your Linux system? Let me guess – you tried various backup systems and hate all of them? Let me show you how to use rsnapshot and an external inexpensive USB drive to back up precious data easily.


I’m a sysadmin in my day job. How could I not care about half decent backups at home. For years I have been running Bacula which has served me half well. An old AIT drive, a couple of tapes, my trusted Adaptec 2940 card and a PostgreSQL-driven Bacula installation worked moderately well but became increasingly cumbersome and fragile. The server (a retired desktop computer) crashed randomly during backups (some ancient SCSI component started to die). Or I forgot to change one of the three needed tapes (as I lacked a changer) in time so that the backup job timeout killed the running backup. Then I had to declare the tapes as free again because cancelling a backup doesn’t make Bacula free the tapes again.Or I played with PostgreSQL and inadvertently killed the director process. So maybe one backup every two weeks really ran through. And restoring files took minutes until the database finally got me the list of files. Finally one of my tapes got stuck in the drive and the drive refused to eject it. Of course the emergency ejection screw did nothing. Enough was enough. So I thought I could use an external USB drive instead of tapes but Bacula did not actually support that. An ancient shell script (vchanger) should emulate a tape changer with USB disk drives. I was too far off from KISS. What in theory sounded like decent hard- and software failed me.


I decided to spend 50€ (the price of one AIT tape) on a 500 GB external USB disk drive and learn about rsnapshot. And in no time I had a simple backup running where I didn’t have to worry about a huge index database and could instantly access any files backed up. What I did:

Format, label and get the UUID

After plugging in the disk for the first time I ran “dmesg” to find out which device the disk was occupying:

[219991.641225] scsi 12:0:0:0: Direct-Access     Seagate  Portable         0130 PQ: 0 ANSI: 4
[219991.641765] sd 12:0:0:0: Attached scsi generic sg4 type 0
[219991.642462] sd 12:0:0:0: [sdc] 976773168 512-byte logical blocks: (500 GB/465 GiB)
[219991.643080] sd 12:0:0:0: [sdc] Write Protect is off
[219991.643083] sd 12:0:0:0: [sdc] Mode Sense: 2f 08 00 00
[219991.643085] sd 12:0:0:0: [sdc] Assuming drive cache: write through
[219991.644964] sd 12:0:0:0: [sdc] Assuming drive cache: write through
[219991.646599]  sdc: sdc1
[219991.694834] sd 12:0:0:0: [sdc] Assuming drive cache: write through
[219991.695212] sd 12:0:0:0: [sdc] Attached SCSI disk

So the disk was at /dev/sdc1. I formatted the disk using

mkfs.ext4 /dev/sdc1

and read the UUID (a unique identifier assigned to each disk while formatting) using

tune2fs -l /dev/sdc1 | grep UUID

which gave me

Filesystem UUID:          44449456-2b13-47df-bfcf-9c5eedf3b287

Set up autofs

You will want to have your USB mounted automatically when you plug it in and use it. On a server there is no plug-and-play like that by default. But the “autofs” software does that well. Install it:

apt-get install autofs

Edit the /etc/auto.master file and add this line:

/var/autofs/removable /etc/auto.usbdrive –timeout=2,sync,nodev,nosuid

Also create an /etc/auto.usbdrive file (that you just pointed to) and add the line into it:

usbdrive -fstype=auto    UUID=44449456-2b13-47df-bfcf-9c5eedf3b287

And finally restart the autofs process:

/etc/init.d/autofs restart

This does not yet mount the disk though. But if you change into the /var/autofs/removable/usbdrive directory then autofs will look for a disk with the given UUID and mount it there on-the-fly. Try it:

cd /var/autofs/removable/usbdrive

You may notice a short delay while autofs mounts the disk. Then you should find yourself on the mounted USB drive. Type “df .” to see the filesystem. It should look like:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sdc1             459G  198M  435G   1% /var/autofs/removable/usbdrive

Install and configure rsnapshot

Install the rsnapshot package:

apt-get install rsnapshot

The default configuration file is located in /etc/rsnapshot.conf. Edit it. But beware that all elements have to be seperated by actual Tabs. I’m using VIM and in my default settings I used “expandtabs” which automatically turned my Tabs into spaces. You don’t want that.

In that file configure “snapshot_root” to point to your autofs directory:

snapshot_root   /var/autofs/removable/usbdrive

Unless you are happy with the default backup times you will want to change the “interval” section. Make sure that you edit the /etc/cron.d/rsnapshot, too, or else rsnapshot won’t run automatically at all. I found the intervals a bit tricky but the the “man rsnapshot” manpage helped me understand it. You can use different names for the different frequencies of backups you run. But the names like “hourly” or “daily” do not mean anything. rsnapshot doesn’t have any association of “hourly” to 60 minutes for example.

My configuration reads:

retain  daily   7
retain  weekly  4

This is much less magical than you might imagine. It just means that if you run “rsnapshot daily” then it will create backups called daily.0 to daily.6 and rotate the numbers on every rsnapshot run. You won’t have more than 7 “daily” directories though which is what you specify in the “retain” line. And you need to make sure that you call “rsnapshot daily” through a crontab. As you can imagine I’m running 7 daily backups (up to one week) and 4 weekly backups (up to one month). So my /etc/cron.d/rsnapshot file has these lines:

30 2      * * *        root    /usr/bin/rsnapshot daily
0  4      * * 1        root    /usr/bin/rsnapshot weekly

Are you unfamiliar with crontab entries? It’s quite easy. You specify the times that you want the certain command run. The columns stand for minute, hour, day of month, month and the day of the week. So my daily job runs at 2:30 at night every day. And the weekly job is run at 4:00 at night on every monday. See “man 5 crontab” for a reference.

Back to your /etc/rsnapshot.conf. Define which directories you want to back up and which you want to have excluded. This is what I use:

backup  /var/       myserver/
backup  /home/      myserver/
backup  /etc/       myserver/
exclude /home/*/tmp/
exclude /home/*/.local/share/Trash/
exclude /home/*/.cache/
exclude /var/lib/mysql/
exclude /var/lib/postgresql/
exclude /var/tmp/
exclude /var/log/
exclude /var/cache/apt/archives/

Of course you can decide to backup your entire server and just exclude evil mount points like /mnt, /dev, /sys, /media and /proc. But in a case of total emergency I’d rather reinstall Debian, install the packages and restore the files. I’m excluding the database directories for MySQL and PostgreSQL here because I cannot just copy the files but need to run a proper backup.

What I also do back up a list of installed Debian packages in case I would need to reinstall:

backup_script   /usr/bin/dpkg –get-selections > packages.txt   installed-packages/

And I backup the databases:

backup_script   /usr/bin/mysqldump –opt –databases mailserver mysql | gzip > mysqldump    mysql/

I have the MySQL root password stored in /root/.my.cnf so I don’t need to mention it here.

Test the rsnapshot configuration

To make sure your configuration is correct run

rsnapshot configtest

Fix any errors until rsnapshot is happy and shows “Syntax OK”.

You can simulate a daily backup by running:

rsnapshot -t daily

It will print out the commands that rsnapshot would run.

Restoring files

If you want to access the files that rsnapshot backed up this is as simple as could be. In /var/autofs/removable/usbdrive/… you will find directories for hourly, daily and weekly backups. Since rsnapshot cleverly uses hardlinks unchanged files barely take up any space. You can just browse around in the respective subdirectories and access your files.

That way you can even buy a second external USB disk drive and put the first disk off-site in case your house burns down, get burglared or your cat pees on the first disk.

Off-site backup

Of course if you lost the one external disk then all your backups would be ruined. So I suggest you get a second external disk and once a month swap them. Depending on your paranoia you can lock them in your bank’s deposit box or give it to your mother-in-law. As opposed to other backup solutions you can just use the second disk without much configuration. Make sure the autofs knows about it and plug it in.


Kudos to Jochen R. who recommended rsnapshot to me.

22 thoughts on “Backups with rsnaphot to external USB drives”

  1. Thanks a lot!

    I spent time with the backup to USB (trying with bacula, unison,…) and now:


    root@server:/# rsnapshot -v daily
    echo 15755 > /var/run/
    mkdir -m 0755 -p /var/autofs/removable/usbdrive/daily.0/
    /usr/bin/rsync -a –delete –numeric-ids –relative –delete-excluded /home \


    Only one thing. The crontab should be an option. e.g. I will connect my disk and run rsnapshot, but normaly the disk is power off.


    Again, thanks a lot.

    Best Regards.

  2. Yet another superb tutorial from you – thank you Christoph.

    I simply followed it as written and it works beautifully.

    I've been looking for a simple solution for ages and this is it.

    Thank you for sharing.

    If I may suggest, if you can find time, could you append how to add a second drive. I'm not sure whether you simply add a second UUID to /etc/auto.usbdrive file, or do you need to create a completely separate path and new file?

    1. OK, the first week has passed and I have a weeks worth of backups on my USB stick – all worked beautifully.

      So now I wish to change USB sticks  to get the second weeks on and at the moment, I'm (partly) at a loss to automate the procedure.

      I tried formatting and adding the new USB sticks UUID to the auto.usbdrive file as a second line, but it failed. I then tried adding a second (independent) path into the auto.master file and created a second (independent) auto.usbdriv1 file with the UUID for the second USB stick and it too failed. The later was not a preferred option, as it still would not be fully automated – the whole point of your method.

      So now I'm at a loss on to how to fully automate the second USB stick.

      As an interim method I returned both the auto.master and auto.usbdrive files back to your tutorial and checked that it all worked as expected – it did. I then renamed the existing auto.usbdrive file (for future use next week) to auto.usbdrive_week1 and created a new auto.usbdrive file with the new USB UUID for this weeks drive and it too is working fine.

      But at the moment, how autofs can auto-mount to the same mount point, two different UUID's remains a mystery to me. While writing this today, I did wonder if comma separated values would work.

      It's actually not the end of the world to do it this way, as in order to cleanly un-mount the USB stick, you have to stop autofs anyway. While you're doing that and swapping the USB sticks, it's not a great deal of trouble to rename the two auto.usbdive files back to what you want and start autofs. It's just it would be good to know if it can be done without the use of complex scripts.

      1. Why not create a new name (backup-disk) with unique UUID and use this one besides the other ?
        You can create a (second) backup so the first usb drive is copied to the backup drive.(think of it as RAID-1)

  3. Hi Crishtopher,

    I found your tutorial while trying to set up rsnapshot, and I’m not sure how to continue as I have no cron.d directory in my /etc/ folder. I’m running this from a QNAP NAS if that makes any difference.

    Can I just create the file and move on from there?


    1. Christoph Haas

      I haven't used a QNAP NAS yet. If it supports "cron" you can put the crontab entries anywhere the system supports it. Either "crontab -e" will let you edit the administrator's (root?) personal crontab. Or /etc/crontab should be the right place.

      1. Hi Christoph,

        Sorry for misspelling your name in my first comment a few months ago!

        I’m back to setting up rsnapshot and would like to know if it’s possible to have multiple jobs running backups (say, one on Tuesday and one on Thursday) each to it’s own drive. I’m not quite sure how to go about that within the crontab file since there’s only one line for rsnapshot. I have a feeling I’m on the right track by creating a 2nd rsnapshot.conf file for the 2nd drive, but am stuck from there.

        Thanks for your help, I appreciate it.


        1. Christoph Haas

          Yes, you can run different jobs. Just add further lines to your /etc/cron.d/rsnapshot crontab file. In addition you will want to create more rsnapshot.conf files under different names. And then in the crontab file you can run rsnapshot with the "-c" option to specify which configuration file you want.

  4. Great article, outlined exactly how I wanted to create my backup system.

    I used most of your work as a reference point, with the exception of using autofs, as my USB drive is automatically mounted in /media.

    I see the reasoning for non-root users to be denied access to the backup directory, but I am weighing whether or not to bypass this safety due to the fact it is only myself using this machine.

    How would I be able to access my backups as a non-root user?

  5. Chris Nicol


    I followed this tutorial on setting up the rsnapshot to an external drive and it worked great. The directions were easy to follow. However, when I tried to add a second drive to the mix is where I became lost. Could you please provide more direction on the autofs settings to add a second USB drive. I was able to format the second drive and get the UUID #, however, from there I am not sure if I need to create a second auto.usbdrive file or where to go.



  6. After I preferom my backup to my 5 TB USB HDD I’m going to be plugging that HDD into a Raspberry Pi 2 and moving the PI2 + HDD outside of my house. I’ll then use SSHFS to mount that HDD that’s connected to the Raspberry Pi to the backup directory in my desktop.
    How can I set rsnapshot so that it will not run unless the remove HDD is mounted? If rsnapshot does run and that drive isn’t mounted I’ll eat up all the space on my desktop. Thanks.

  7. It is very bad that you don’t add a date to articles. It’s useless now – how do I know which parts are out of date and which are not?

    1. Christoph Haas

      There are surely more polite ways to ask for adding dates to articles. Why is this article suddenly useless? Do you want your money back? Sheesh.

  8. Hello Christoph,

    thanks for your nice article. I’m wondering, if changing usb-drives could be a problem in some (worst) cases. For example, what happens, when the command “rsnapshot monthly” is always running just after changing from disk A to disk B? Then perhaps an really old weekly backup on disk B (!) — instead of the newer weekly backup on disk A — is moved to monthly.0 -directory. And when crashing disk B, there perhaps are no monthly backups to jump back in time earlier than one month (when weekly.0 till weekly.3 is covering the last month on disk A). Isn’t it better to use only disk A for snapshot-backups and — in a second step — mirroring disk A to disk B somewhere else? What do you think?


  9. Hello Christoph.
    Thank you so much. This helped me a lot!
    Great explanation and useful examples.

    Just for completeness:
    on CENTOS you have to install EPEL Repo first before you can get rsnapshot

    yum -y install epel-release
    yum repolist
    yum install rsnapshot

  10. Thanks for this Christoph.

    I used this solution to back up an Ubuntu (18.04) VMware Fusion guest to a USB drive running on a macbook pro. I formatted the drive as explained above. When you plug in the drive it is mounted under /media/username/UUID. I changed snapshot_root in /etc/rsnapshot.conf to:

    snapshot_root /UUID/usb

    I prefer to do my backups manually and not have to worry about a schedule when I’m travelling so I added the following to the end of rsnapshot.conf.

    backup / usb
    exclude /mnt
    exclude /dev
    exclude /media
    exclude /proc
    retain monthly 30
    retain adhoc 365

    Backing up practically the whole system is probably overkill but, given the amount of time it takes and the backup drive (2TB) space consumed, I’m happy with having more potential restore candidates.

    I’m also looking into Cronopete for incrementals. I’ve found time machine on the mac to be very helpful every so often and Cronopete seems to provide very similar functionalithy.


  11. Ratko Perlic

    There is formatting error in /usr/bin/dpkg –get-selections . Two dashes are combined in one long so simple copy/paste will not work.
    Also, in order to have packages.txt ready for usage bit more complex backup string can be used:
    backup_script /usr/bin/dpkg –get-selections | /bin/sed -e ‘s/install//’ | /bin/sed -e ‘s/\t//g’ | /usr/bin/tr ‘\n’ ‘ ‘ > packages.txt installed-packages/

    1. Ratko Perlic

      And same formatting self correcting happened to my comment also…
      To summarize, get-selections should be preceded by two dashes and last two quotes in /usr/bin/tr should have space between them. Also, don’t forget to separate backup_script and /usr/bin/dpkg with tab instead of space. Tab also should be used between packages.txt and installed-packages/

  12. you defined “weekly” after “daily”. so, as far as i understand rsnapshots manpage, your daily.6 will rotate into weekly.0 … and calling two different backup jobs results in two different backup data. that is not what i would expect of correct aged backups.

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