Installing BitTorrent Sync on Raspberry PiA detailed tutorial on setting up your Pi to run a replacement for Dropbox

There are many solutions to build your own cloud like Seafile, ownCloud or clouddav. Those are great solutions, but all rely on a central server; if this server is turned off or crashes, sync will no longer work. Bittorrent Sync is different: it syncs content using peer-to-peer file sharing. You can read about Bittorrent Sync here.

This tutorial shows how to install Bittorrent Sync on Rasperry Pis.

What you need

The standard Raspberry Pi hardware will do:

  • Raspberry Pi Model B (or the model A with USB ethernet or wlan interface)
  • USB power supply
  • SD card
  • SD card writer
  • (optional) Raspberry Pi enclosure

I’m using Window as my host system but all steps except for writing the ISO image are the same on all platforms. The following software is used for this tutorial:

  • Putty, to connect to the Raspberry Pi with SSH. You don’t necessarily need SSH if you hook up your Raspberry Pi to a monitor and keyboard.
  • Nmap: I’m doing a completely headless raspbian install (i.e., without ever connecting the device to a monitor and keyboard). To SSH to the device I’m first using Nmap to find out the IP address of my Raspberry Pi. Again this is not necessary if you connect the device to a monitor. There are also plenty of other ways to find out the IP – or you might connect to the Pi using it’s default hostname raspberry
  • I’m using Raspbian as the operating system.
  • The Raspbian image is written to the SD card using Win32DiskImager.

Part 1: Installing and Configuring the Raspberry Pi

If you already have a Rasperry Pi running, then the following steps are not necessary and you can jump right to Part 2.

  1. Download the Raspbian ISO.
  2. Download Win32DiskImager which allows you to write the ISO file to the SD card.
  3. Insert the SD card into your SD card writer.
  4. Run Win32DiskImage as administrator.
  5. Select the Raspbian image as Image File and the device letter of your SD card as Device. Warning: make sure not to select any external hard disks as the Device; this might lead to data loss on the selected device.

  6. Click Write and confirm it’s the right device by clicking Yes:

  7. It might take some time to write the ISO. Upon completion you should see the following message:

  8. Put the SD card into Raspberry PI, connect the device to your network, and power on the device by plugging in the USB power supply cable.

  9. Wait around one minute to let the device boot. Then find out its IP using Nmap

     C:\>nmap -sn
     Starting Nmap 6.40 ( ) at 2014-05-01 19:34 W. Europe Daylight Time
     Nmap scan report for
     Host is up (0.11s latency).
     Nmap scan report for
     Host is up (0.028s latency).
     Nmap scan report for raspberrypi.lan (
     Host is up (0.068s latency).
     Nmap scan report for xxxxxxxxxxx.lan (
     Host is up (0.0040s latency).
     Nmap done: 256 IP addresses (4 hosts up) scanned in 14.88 seconds

    In my case the Raspberry got</li>

  10. Connect to the device using SSH (the default password is raspberry):

    C:\>ssh pi@
    The authenticity of host ' (' can't be established.
    RSA key fingerprint is 35:33:47:1d:f3:6b:6e:3a:2f:cf:17:d8:e1:d5:02:6f.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added '' (RSA) to the list of known hosts.
    pi@'s password:
    Linux raspberrypi 3.10.25+ #622 PREEMPT Fri Jan 3 18:41:00 GMT 2014 armv6l
    The programs included with the Debian GNU/Linux system are free software;
    the exact distribution terms for each program are described in the
    individual files in /usr/share/doc/*/copyright.
    Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
    permitted by applicable law.
    NOTICE: the software on this Raspberry Pi has not been fully configured. Please run 'sudo raspi-config'
    pi@raspberrypi ~ $
  11. Change the password from the current raspberry to something a little harder to guess:

    pi@raspberrypi ~ $ passwd
    Changing password for pi.
    (current) UNIX password:
    Enter new UNIX password:
    Retype new UNIX password:
    passwd: password updated successfully
  12. Expand the filesystem so it uses the entire SD card space. The easiest way to do so is using the rasp-conf tool. Start it as follows:

    pi@raspberrypi ~ $ sudo raspi-config

    In the screen that shows up select the first option Expand Filesystem:

    After the operation finishes select to reboot the device or do so manually by:

    pi@raspberrypi ~ $ sudo reboot
  13. Rebooting the device will terminate your SSH connection. Reconnect with:

    C:\>ssh pi@
  14. Once connected switch to root:

    pi@raspberrypi ~ $ sudo -i
  15. Now set the timezone by copying the zoneinfo of your country to localtime:

    root@raspberrypi:~# cp /usr/share/zoneinfo/Europe/Zurich  /etc/localtime

    You can see a list of available locations by hitting the tab key twice, e.g., if you are in Europe hitting tab device after having entered cd /usr/share/zoneinfo/Europe gives you a list of countries:

    root@raspberrypi:~# cp /usr/share/zoneinfo/Europe/
    Amsterdam    Bratislava   Copenhagen   Istanbul     London       Monaco       Prague       Simferopol   Tiraspol     Volgograd
    Andorra      Brussels     Dublin       Jersey       Luxembourg   Moscow       Riga         Skopje       Uzhgorod     Warsaw
    Athens       Bucharest    Gibraltar    Kaliningrad  Madrid       Nicosia      Rome         Sofia        Vaduz        Zagreb
    Belfast      Budapest     Guernsey     Kiev         Malta        Oslo         Samara       Stockholm    Vatican      Zaporozhye
    Belgrade     Busingen     Helsinki     Lisbon       Mariehamn    Paris        San_Marino   Tallinn      Vienna       Zurich
    Berlin       Chisinau     Isle_of_Man  Ljubljana    Minsk        Podgorica    Sarajevo     Tirane       Vilnius

    The timezone should be set after a reboot (no need to do it right now). You can check the local time with:

    root@raspberrypi:~$ date
    Thu May  1 19:58:11 CEST 2014
  16. If you want set a fixed IP for your raspberry by editing /etc/network/interfaces. Change the original file:

    root@raspberryroot:~# cat /etc/network/interfaces
    auto lo
    iface lo inet loopback
    iface eth0 inet dhcp
    allow-hotplug wlan0
    iface wlan0 inet manual
    wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
    iface default inet dhcp
    (Gateway Address from Nmap Scan)

    to something like that (I’m using the IP with gateway

    root@raspberryroot:~# vi /etc/network/interfaces
    root@raspberryroot:~# cat /etc/network/interfaces
    auto lo
    iface lo inet loopback
    iface eth0 inet static

    To make the change effective (there’s no need to do so now) you can execute:

    root@raspberryroot:~# ifdown eth0 &#038;&#038; ifup eth0

    You’ll need to reconnect after changing the IP</li>

  17. When you reconnect after changing the IP you might get the following warning

    C:\>ssh pi@
    Someone could be eavesdropping on you right now (man-in-the-middle attack)!
    It is also possible that the RSA host key has just been changed.
    The fingerprint for the RSA key sent by the remote host is
    Please contact your system administrator.
    Add correct host key in /cygdrive/c/Users/Noon/.ssh/known_hosts to get rid of this message.
    Offending key in /cygdrive/c/Users/Noon/.ssh/known_hosts:1
    RSA host key for has changed and you have requested strict checking.
    Host key verification failed.

    If you get the message on Windows, open the file given in the error message, e.g., c:/User/Noon/.ssh/known_hosts. Delete all entries related to your Raspberry Pi. In my case I had to remove the lines: ssh-rsa AAAAB3NzaC1yc2E... ssh-rsa AAAAB3NzaC1yc2E...

    After that you should be able to connect again:

    C:\>ssh pi@
    The authenticity of host ' (' can't be established.
    RSA key fingerprint is 35:33:47:1d:f3:6b:6e:3a:2f:cf:17:d8:e1:d5:02:6f.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added '' (RSA) to the list of known hosts.
    pi@raspberrypi ~ $ sudo -i
  18. Optionally you might want to add additional DNS servers. You can do so by editing /etc/resolv.conf. For example, to add the Google DNS at

    root@raspberrypi:~# cat /etc/resolv.conf
    domain lan
    search lan
    root@raspberrypi:~# vi /etc/resolv.conf
    root@raspberrypi:~# cat /etc/resolv.conf
    domain lan
    search lan
  19. You also might want to change the hostname of your Pi. You’ll need to edit two files. First, change the hostname in /etc/hostname:

    root@raspberrypi:~# cat /etc/hostname
    root@raspberrypi:~# echo "bittorrentsync" > /etc/hostname
    root@raspberrypi:~# cat /etc/hostname

    Next, change the name in the last line of /etc/hosts:

    root@raspberrypi:~# vi /etc/hosts
    root@raspberrypi:~# cat /etc/hosts       localhost
    ::1             localhost ip6-localhost ip6-loopback
    fe00::0         ip6-localnet
    ff00::0         ip6-mcastprefix
    ff02::1         ip6-allnodes
    ff02::2         ip6-allrouters
  20. To finish up the setup process update your Pi with

    apt-get update &#038;&#038; apt-get upgrade

The next part is about installing Bittorrent Sync.

Part 2: Installing and Configuring Bittorrent Sync

  1. For security reasons it’s always a good idea to create separate users to run btsync. Create the user with:

     root@raspberrypi:~# adduser --quiet --system --group --disabled-password btsync
  2. Next download Bittorrent Sync:

     root@raspberrypi:~# wget
     --2014-05-01 20:44:00--
     Resolving (
     Connecting to (||:80... connected.
     HTTP request sent, awaiting response... 200 OK
     Length: 2241312 (2.1M) [application/x-gzip]
     Saving to: `btsync_arm.tar.gz'
     100%[==================================================================================================================>] 2,241,312    834K/s   in 2.6s
     2014-05-01 20:44:03 (834 KB/s) - `btsync_arm.tar.gz' saved [2241312/2241312]
  3. Extract the file to /usr/local/sbin/:

     root@bittorrentsync:~# tar -xvf btsync_arm.tar.gz -C /usr/local/sbin btsync

    You can then delete the download:

     root@bittorrentsync:~# rm -f btsync_arm.tar.gz
  4. Bittorrent sync uses a single configuration file to store its setting. Create this file with:

     root@bittorrentsync:~# /usr/local/sbin/btsync --dump-sample-config > /etc/btsync.conf
  5. Now it’s time to start up btsync:

     root@raspberrypi:~# /usr/local/sbin/btsync
     BitTorrent Sync forked to background. pid = 2232
  6. Bittorrent Sync gives you a nice web interface. Open up the webinterface on your host system by entering the IP address of your PI, followed by colon, followed by the port 8888 in your browser. For example, to reach my Pi I used

  7. The webinterface will first ask you to agree to the privacy policy and terms:

  8. Next you have to enter a admin password:

  9. Login with user admin and the password you just set:

  10. After that you should see an interface where you can add folders you like to sync:

  11. First create a test folder on our Pi (make sure to give ownership to btsync, he’ll be the one running btsync later on):

    root@raspberrypi:~# mkdir -p  /home/btsync/sync/test  
    root@raspberrypi:~# chown btsync:btsync /home/btsync/sync/test/
  12. Next add this folder with the add folder option in the webinterface. You should get the following dialog:

    Click Generate to create a folder secret or enter a custom password. Then select the test folder /home/btsync/sync/test

  13. On your host system install Bittorrent Sync too. Under My Sync click add folder and enter the same secret as on your Pi. You can get the secret at any time by clicking Secret / QR on the web interface. Select an empty test folder to be synced:

  14. Back on your Raspberry also create a test file in the folder that should be synced:

    root@raspberrypi:~# echo "test" > /home/btsync/sync/test/test_raspberry.txt
  15. The webinterface on Pi should show your host system, and the two folders should start syncing.

    root@raspberrypi:~# ls -l /home/btsync/sync/test/
    total 8
    -rw-r--r-- 1 root root 14 May  1 21:04 file_on_windows.txt
    -rw-r--r-- 1 root root  5 May  1 21:05 test_raspberry.txt
  16. Bittorrent Sync works as expected, but we started the process manually. To make btsync start as a service on boot, I’m using the following init script from

    #! /bin/sh
    # Provides: btsync daemon
    # Required-Start: $syslog
    # Required-Stop: $syslog
    # Default-Start: 2 3 4 5
    # Default-Stop: 0 1 6
    # Short-Description: BTSync server daemon
    # Description: Daemon script to run a BTSync permanent peer
    # Placed in /etc/init.d.
    # Author: Nicolas Bernaerts &lt;>
    # Version:
    #  V1.0, 06/09/2013 - Creation
    #  V1.1, 09/09/2013 - Use under-priviledged system user
    # description variables
    DESC="BTSync server"
    # Exit if btsync program is not installed
    if [ ! -x "$DAEMON" ] ; then
    echo "Binary $DAEMON does not exist. Aborting"
    exit 0
    # Exit if btsync user home directory doesn't exist
    if [ ! -d "$ROOT" ]; then
    echo "User $USER does not exist. Aborting"
    exit 0
    # Function that starts the daemon/service
    # 0 - daemon started
    # 1 - daemon already running
    # 2 - daemon could not be started
    # If needed, start the daemon
    if [ -f "$PIDFILE" ]
        echo "$NAME already running"
        start-stop-daemon --start --quiet --chuid $USER --name $NAME --exec $DAEMON -- --config /etc/btsync.conf
        [ "$RETVAL" = "0" ] &#038;&#038; echo "$NAME started"
    return "$RETVAL"
    # Function that stops the daemon/service
    # 0 - daemon stopped
    # 1 - daemon already stopped
    # 2 - daemon could not be stopped
    # Stop the daemon
    start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE --name $NAME
    [ "$RETVAL" = "0" ] &#038;&#038; echo "$NAME stopped"
    [ "$RETVAL" = "1" ] &#038;&#038; echo "$NAME was not running"
    # remove pid file
    rm -f $PIDFILE
    return "$RETVAL"
    # deal with different parameters : start, stop &#038; status
    case "$1" in
    # start service
    # stop service
    # restart service
    # unknown command, display help message
        echo "Usage : $SCRIPTNAME {start|stop|restart}" >&#038;2
        exit 3

    Copy or download the script to /etc/init.d/btsync and make it executable:

    root@raspberrypi:~# wget -O /etc/init.d/btsync
    root@raspberrypi:~# chmod +x /etc/init.d/btsync
  17. To test the init.d script, first terminate the running btsync process:

    root@raspberrypi:~# ps aux | grep btsync
    root      2232  0.7  0.9  71052  4368 ?        Ssl  20:48   0:09 /usr/local/sbin/btsync
    root      2314  0.0  0.1   3544   808 pts/0    S+   21:11   0:00 grep btsync
    root@raspberrypi:~# kill 2232

    Then try starting the service:

    root@raspberrypi:~# service btsync start
    Storage path specified in config file does not exist.

    Oops! We need to configure the storage path first.</li>

  18. To set the storage path, edit the config file /etc/btsync.conf:

    root@raspberrypi:~# vi /etc/btsync.conf

    change line “storage_path” : “/home/user/.sync”, to “storage_path” : “/home/btsync/.sync”,. Then create this folder with:

    root@raspberrypi:~# mkdir /home/btsync/.sync
    root@raspberrypi:~# chown btsync:btsync /home/btsync/.sync
  19. Now try to run the service again:

    root@raspberrypi:~# service btsync start
    By using this application, you agree to our Privacy Policy and Terms.
    BitTorrent Sync forked to background. pid = 2406
    btsync started

    Great! The startup script works.</li>

  20. Edit: To make btsync start on boot run the following command:

    root@raspberrypi:~# update-rc.d btsync defaults

    You are all set. After a reboot the service user btsync should be running Bittorrent Sync.</li> </ol>

Bonus: Add external USB storage

One of the great benefits of Bittorrent Sync is having as much space as your harddisk give. The SD cards tend to be rather small, so let’s add an external USB drive to our Pi.

  1. First, attach the USB drive. Make sure to use a powered USB hub if your drive is powered by USB, since the Pi will likely not be able to provide the necessary power.
  2. Next run dmesg to find out the device name:

     root@bittorentsync:~# dmesg | tail -n 17 
     [  183.561127] usb 1- new high-speed USB device number 6 using dwc_otg
     [  183.662980] usb 1- New USB device found, idVendor=1058, idProduct=10a8
     [  183.663016] usb 1- New USB device strings: Mfr=1, Product=2, SerialNumber=3
     [  183.663036] usb 1- Product: Elements 10A8
     [  183.663056] usb 1- Manufacturer: Western Digital
     [  183.663075] usb 1- SerialNumber: 575845314138333837343534
     [  183.664124] usb-storage 1- USB Mass Storage device detected
     [  183.668404] scsi0 : usb-storage 1-
     [  184.662618] scsi 0:0:0:0: Direct-Access     WD       Elements 10A8    1042 PQ: 0 ANSI: 6
     [  184.664248] sd 0:0:0:0: [sda] 976707584 512-byte logical blocks: (500 GB/465 GiB)
     [  184.665318] sd 0:0:0:0: [sda] Write Protect is off
     [  184.665354] sd 0:0:0:0: [sda] Mode Sense: 53 00 10 08
     [  184.666263] sd 0:0:0:0: [sda] No Caching mode page found
     [  184.666293] sd 0:0:0:0: [sda] Assuming drive cache: write through
     [  184.669613] sd 0:0:0:0: [sda] No Caching mode page found
     [  184.669648] sd 0:0:0:0: [sda] Assuming drive cache: write through
     [  188.195701]  sda: sda1

    In my case the external drive sits at /dev/sda1

  3. If you want to reformat your drive, make sure it is not mounted first:

     root@bittorentsync:~# sudo umount /dev/sda1

    then format it with

     root@bittorentsync:~# sudo mkfs.ext4 /dev/sda1 -L Sync
  4. If your drive is ready you can mount it with:

     root@bittorentsync:~# sudo mount -t ext4 /dev/sda1 /media/USBDRIVE/
  5. To probably want to make the device mount automatically on reboot. To this end, first find out the id of the device with:

     root@bittorentsync:~# ls -l /dev/disk/by-uuid/
     total 0
     lrwxrwxrwx 1 root root 15 Jan  1  1970 993B-8922 -> ../../mmcblk0p1
     lrwxrwxrwx 1 root root 10 May  1 21:20 e0bcd6da-6cf3-47eb-8c94-82e0a85c7392 -> ../../sda1
     lrwxrwxrwx 1 root root 15 May  1 21:17 fc254b57-8fff-4f96-9609-ea202d871acf -> ../../mmcblk0p2

    In my case the device has the id e0bcd6da-6cf3-47eb-8c94-82e0a85c7392</li>

  6. You need to add the id from the previous step to the fstab file. Make a backup of this file first:

     root@bittorentsync:~# sudo cp /etc/fstab /etc/fstab.backup
  7. After you backed up the file add your device id to fstab by adding a line similar to

     UUID=e0bcd6da-6cf3-47eb-8c94-82e0a85c7392 /media/USBDRIVE ext4 rw, defaults 0 0

    e.g, the file shoud look like:

     proc            /proc           proc    defaults          0       0
     /dev/mmcblk0p1  /boot           vfat    defaults          0       2
     /dev/mmcblk0p2  /               ext4    defaults,noatime  0       1
     UUID=e0bcd6da-6cf3-47eb-8c94-82e0a85c7392 /media/USBDRIVE ext4 rw, defaults 0 0</ol> 

    That’s it. Now the external drive should be mounted automatically and you have plenty of space to sync.

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