GNet Solutions » GNU/Linux Administration

• Table of contents
• Device Identification
• Sync Script
• Systemd Service
• Udev Rule
• Resources

Once in a while I will need to do a two-way synchronization of the contents of an owncloud sync folder to a specific USB drive, and having this task done automagically by systemd.

NOTE: The USB drive used in this guide is FAT32. If using NTFS, you must install the ntfs-3g-fuse package from the AUR.

• Make sure rsync is installed:
  

  sudo pacman -S rsync
  

Device Identification¶

• Get the list of drives:
  

  sudo fdisk -l
  

• Start by getting the device label:
  

  sudo blkid /dev/sdb1
  

• Create a label for the USB drive:
  

  sudo dosfslabel /dev/disk/by-uuid/ACE7-1996 "SYNCSHARE" 
  

• Make a temporary mount directory:
  

  sudo mkdir /media/SYNCSHARE
  

• Edit the fstab file:
  

  sudo nano /etc/fstab
  

  • Add an fstab entry for the SYNCSHARE device:
    

    UUID=ACE7-1996    /media/SYNCSHARE    vfat    users,noauto    0 0
    

Sync Script¶

• Create a simple two-way rsync script:
  

  sudo nano /usr/local/bin/syncshare.sh
  

  • And add the following
    

    #!/bin/sh
    # Script to do a two-way sync with a USB drive
    
    if [ $(mount | grep -c /media/SYNCSHARE) != 1 ]
    then
      /sbin/mount /dev/disk/by-uuid/ACE7-1996 || exit 1
      echo "/media/SYNCSHARE is now mounted" 
    
      rsync -rtuv --modify-window=1 --size-only --exclude ".csync*" --exclude ".owncloud*" /media/SYNCSHARE/owncloudshare/ /home/bob/owncloudshare/
      rsync -rtuv --modify-window=1 --size-only --exclude ".csync*" --exclude ".owncloud*" --delete /home/bob/owncloudshare/ /media/SYNCSHARE/owncloudshare/
    
      sync
    
      sudo -u bob DISPLAY=:0 DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus notify-send "SYNCSHARE Finished Synchronizing!" 
    
      sleep 5
    
      umount /media/SYNCSHARE
    else
      rsync -rtuv --modify-window=1 --size-only --exclude ".csync*" --exclude ".owncloud*" /media/SYNCSHARE/owncloudshare/ /home/bob/owncloudshare/
      rsync -rtuv --modify-window=1 --size-only --exclude ".csync*" --exclude ".owncloud*" --delete-delay /home/bob/owncloudshare/ /media/SYNCSHARE/owncloudshare/
    
      sync
    
      sudo -u bob DISPLAY=:0 DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus notify-send "SYNCSHARE Finished Synchronizing!" 
    
      sleep 5
    
      umount /media/SYNCSHARE
    fi
    

    
    NOTE: Adding the -n flag to the rsync commands will help when testing whether or not the script will run correctly.
    NOTE: Make sure to change the username and uid number to the correct values for the notify-send commands.
    NOTE: FAT filesystems require the --modify-window=1 --size-only flags in order to synchronize correctly.

• Then make it executable:
  

  sudo chmod +x /usr/local/bin/syncshare.sh
  

Systemd Service¶

• Create a systemd unit file:
  

  sudo nano /etc/systemd/system/syncshare.service
  

  • And add the following:
    

    [Unit]
    Description=SyncShare trigger
    Requires=dev-disk-by\x2dlabel-SYNCSHARE.device
    After=dev-disk-by\x2dlabel-SYNCSHARE.device
    
    [Service]
    ExecStart=/usr/local/bin/syncshare.sh
    
    [Install]
    WantedBy=dev-disk-by\x2dlabel-SYNCSHARE.device
    

• And reload the systemd daemon:
  

  sudo systemctl daemon-reload
  

• Enable the syncshare service:
  

  sudo systemctl enable syncshare
  

Udev Rule¶

• List the attached USB devices and get the vendor and product IDs:
  

  lsusb
  

  • Example output:
    

    Bus 003 Device 004: ID 0781:3528 SanDisk Corp. Cruzer
    

    
    NOTE: The above example uses 0781 Vendor ID and 3528 Product ID.

• Add a udev rule to start the syncshare systemd service on device hotplug:
  

  sudo nano /etc/udev/rules.d/99-local.rules
  

  • And add the following:
    

    SUBSYSTEMS=="usb", ATTRS{idVendor}=="0781", ATTRS{idProduct}=="3528", ACTION=="add", TAGS+="systemd", ENV{SYSTEMD_WANTS}=="syncshare.service" 
    

• Restart udev:
  

  sudo systemctl restart systemd-udevd
  

Resources¶

• http://serverfault.com/questions/766506/automount-usb-drives-with-systemd
• https://bbs.archlinux.org/viewtopic.php?id=207050
• https://bbs.archlinux.org/viewtopic.php?id=192461
• https://wiki.archlinux.org/index.php/Persistent_block_device_naming#by-label
• https://askubuntu.com/questions/25071/how-to-run-a-script-when-a-specific-flash-drive-is-mounted/190366
• http://jasonwryan.com/blog/2014/01/20/udev/
• https://wiki.archlinux.org/index.php/NTFS-3G#Manual_mounting