Raspberry Pi Install Java 8 SDK and OpenHab 2 on Raspberry Pi Desktop for RPI 4

I wanted to install OpenHab 2 on my RPI 4 which is running the latest Raspberry Pi Desktop. But I was missing Java 8 which is a prerequisite and unfortunately not available anymore as a stable version, for Debian 10, due to a security issue.

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First, here is the version of Raspberry Pi Desktop I have:

$ cat /etc/os-release
PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION="10 (buster)"

Trying to install Java 8 SDK was resulting in errors like:

$ sudo apt-get install openjdk-8-jdk
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package

Or like:

Reading package lists... Done
Building dependency tree
Reading state information... Done
Package openjdk-8-jdk is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
E: Package 'openjdk-8-jdk' has no installation candidate

My Package sources were:

deb http://ftp.debian.org/debian/ buster main contrib non-free
deb http://security.debian.org/ buster/updates main contrib non-free
deb http://ftp.debian.org/debian/ buster-updates main contrib non-free

The solution was to add a new source with the 'unstable' arm-hf packages in /etc/apt/sources.list.d/raspi.list ('sid' is the codename for unstable):

$ echo 'deb http://ftp.debian.org/debian sid main' | sudo tee -a /etc/apt/sources.list.d/

Next, do:

$ sudo apt-get update
$ sudo apt install gcc-8-base
$ sudo apt-get install openjdk-8-jdk

NB.: without installing gcc-8-base, you would get an error like this :

Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
libc6-dev : Breaks: libgcc-8-dev (< 8.4.0-2~) but 8.3.0-6+rpi1 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.


Now, you can install OpenHab 2:

$ wget -qO - 'https://bintray.com/user/downloadSubjectPublicKey?username=openhab' | sudo apt-key add -
$ sudo apt-get install apt-transport-https
$ echo 'deb https://dl.bintray.com/openhab/apt-repo2 stable main' | sudo tee /etc/apt/sources.list.d/openhab2.list
$ sudo apt-get update

If you get an error like this one:

E: The repository 'https://openhab.jfrog.io/openhab/openhab-linuxpkg unstable Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Then do:

$ echo 'deb [trusted=yes] https://dl.bintray.com/openhab/apt-repo2 stable main' | sudo tee /etc/apt/sources.list.d/openhab2.list

Finally, do:

$ sudo apt-get install openhab2
$ sudo apt-get install openhab2-addons
$ sudo systemctl daemon-reload
$ sudo systemctl enable openhab2.service
$ sudo adduser openhab dialout
$ sudo adduser openhab tty

Edit /etc/default/openhab2 to add access for Java to the serial ports (ex.:for Zwave keys)

$ nano /etc/default/openhab2 


It should output:

openhab2.service - openHAB 2 - empowering the smart home
Loaded: loaded (/usr/lib/systemd/system/openhab2.service; disabled; vendor preset: enabled)
Active: active (running) since Wed 2020-07-15 21:57:07 BST; 28min ago
Docs: https://www.openhab.org/docs/
Main PID: 26101 (java)
Tasks: 101 (limit: 4915)
Memory: 212.3M
CGroup: /system.slice/openhab2.service
└─26101 /usr/bin/java -Dopenhab.home=/usr/share/openhab2 -Dopenhab.conf=/etc/openhab2 -Dopenhab.runtime=/usr/share/openhab2/runtime -Dopenhab.userdata=/var/lib/openhab2 -Dopenhab.logdir=/var/log/openhab2 -Dfelix.cm.dir=/var/li

Jul 15 21:57:07 Helios systemd[1]: Started openHAB 2 - empowering the smart home.


As far as I am concerned, I share via smb the various folders

Edit /etc/samba/smb.conf

$ sudo nano /etc/samba/smb.conf

[openHAB2-userdata]comment=openHAB2 userdata
only guest=no
create mask=0777
directory mask=0777

[openHAB2-conf]comment=openHAB2 site configuration
only guest=no
create mask=0777
directory mask=0777

[openHAB2-logs]comment=openHAB2 logs
only guest=no
create mask=0777
directory mask=0777

[openHAB2-backups]comment=oepnHAB2 backups
only guest=no
create mask=0777
directory mask=0777

Restart the Samba service:

$ sudo systemctl restart smbd.service


Start openHab with:

$ sudo systemctl start openhab2.service
$ sudo systemctl status openhab2.service

It can take 15' to be initialized, but soon you should be able to access openHab on your RPI on port 8080!


Do a backup with:

$ sudo ./usr/share/openhab2/runtime/bin/backup

Restore a backup with:

$ sudo systemctl stop openhab2.service
$ sudo ./usr/share/openhab2/runtime/bin/restore /var/lib/openhab2/backups/openhab2-backup-....
$ sudo systemctl start openhab2.service

It will take long minutes to restart!


More details about installing openHAb on Linux on the official page.

Et voilà!

Raspberry Pi Use a Z-Wave Controller USB Key with openHAB in Docker on a RPI 4

It took me quite some hours to be able to use my Aeotec Z-Stick Gen5 (ZW090) key within my Docker image of openHAB, running on a Raspberry Pi 4 (with a Raspberry Pi OS). Here are all the tips I used.

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First, before plugging the controller  in your RPI, configure it to see the Serial Ports. Connect onto your RPI within a SSH Console (ex.: via Putty)  and type the command:

sudo raspi-config

Use "5 interfacing Options" > "P6 Serial" > "Yes" > "Ok"

And now reboot.

Next, back into a SSH conscole, check what USB devices already exists with the command:


Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

And flush the kernel and boot logs:

sudo dmesg -c >> ~/dmesg-`date +%d%m%Y`.log

Then, plug your Z-Wave Controller USB Key in a USB Port and check that it's detected and mounted properly:


Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 009: ID 0658:0200 Sigma Designs, Inc. Aeotec Z-Stick Gen5 (ZW090) - UZB
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


[ 3124.779069] usb 1-1.4: new full-speed USB device number 9 using xhci_hcd
[ 3124.919928] usb 1-1.4: New USB device found, idVendor=0658, idProduct=0200, bcdDevice= 0.00
[ 3124.919942] usb 1-1.4: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[ 3124.919953] usb 1-1.4: SerialNumber: 32303136-3131-3033-3030-303031383932
[ 3124.926704] cdc_acm 1-1.4:1.0: ttyACM0: USB ACM device


"lsusb" should show you a new device. Ex.: Aeotec Z-Stick Gen5 (ZW090) - UZB.

And "dmesg" must should you the mount point: cdc_acm 1-1.4:1.0: ttyACM0: USB ACM device.

If you don't see the mount point, then you possibly have a device not supported by the RPI 4. It seems that it is the case with the old Aeotec "Z-Stick Gen5". "New Z-Stick Gen5" and "Z-Stick Gen5+" should however be compatible. But there is a trick: plug your key on the RPI 4 via a USB HUB (2.0 or 3.0).

I presume that the Docker Image is already up and running. If not, install it.

sudo useradd -r -s /sbin/nologin openhab
usermod -a -G openhab pi
mkdir /opt/openhab
mkdir /opt/openhab/conf
mkdir /opt/openhab/userdata
mkdir /opt/openhab/addons
chown -R openhab:openhab /opt/openhab

Check the id of the user openhab with:

id openhab

uid=999(openhab) gid=994(openhab) groups=994(openhab)

Grant access on the Serial Port for the user 'openhab':

sudo chmod 777 /dev/ttyACM0
sudo chown openhab /dev/ttyACM0

And use the uid and gid found above in the following command, setting the ttyA* found previously and specifying the version to be used:

docker run --name openhab --net=host --device=/dev/ttyACM0 -v /etc/localtime:/etc/localtime:ro -v /etc/timezone:/etc/timezone:ro -v /opt/openhab/conf:/openhab/conf -v /opt/openhab/userdata:/openhab/userdata -v /opt/openhab/addons:/openhab/addons -d -e USER_ID=<uid> -e GROUP_ID=<gid> --restart=always openhab/openhab:latest


Now, using Portainer (because it's easy), open a console within openhab... Portainer is not yet installed ? Do it with:

docker run -d -p 9000:9000 -p 8000:8000 --name portainer1 --restart always -v /var/run/docker.sock:/var/run/docker.sock -v portainer:/data portainer/portainer:latest

Go to the page http://<Your RPI IP>:9000, open the Containers and click on the "Exec Console" icon of 'openhab' container:

Grant the same accesses inside the image than on the RPI:

sudo chmod 777 /dev/ttyACM0
sudo chown openhab /dev/ttyACM0

chown -R openhab:openhab /opt/openhab

Now restart the 'openhab' container (with the icon Restart ;) ). It will take some minutes to be available. But once you can get into it, go to the Things and configure the Controller to use the Serial Port ttyACM0:


Et voilà

Raspberry Pi Raspberry Pi's SD card full ?

Trying to update one of my Raspberry Pi Desktop, I see messages pretending that there is not enough free space ? 

Click to Read More

I saw that my Pi was full when I tried to update it with

sudo apt-get update && sudo apt-get upgrade -y

 Error writing to output file - write (28: No space left on device)

I could also see that there was no free storage anymore as the system was unable to allocate the swap file:

systemctl status dphys-swapfile.service

dphys-swapfile.service - dphys-swapfile - set up, mount/unmount, and delete a swap file
Loaded: loaded (/lib/systemd/system/dphys-swapfile.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Sun 2020-06-28 12:35:15 BST; 4min 21s ago
[...]Jun 28 12:35:15 helios dphys-swapfile[327]: want /var/swap=100MByte, restricting to 50% of remaining disk size: 0MBytes
Jun 28 12:35:15 helios systemd[1]: Failed to start dphys-swapfile - set up, mount/unmount, and delete a swap file.

And indeed, the swap file was 0B:

free -h

      total   used   free   shared  buff/cache  available
Mem: 3.8Gi 285Mi 2.7Gi 11Mi    886Mi       3.4Gi
Swap: 0B      0B     0B

Start to investigate with:

sudo df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/root 29G 29G 0 100% /
devtmpfs 1.8G 0 1.8G 0% /dev
tmpfs 2.0G 0 2.0G 0% /dev/shm

Or use the version for Inode which won't include the mounted drives

sudo df -i

Filesystem Inodes  IUsed  IFree   IUse% Mounted on
/dev/root 1895552 328167 1567385 18% /
devtmpfs 117763 409 117354 1% /dev
tmpfs 183811 1 183810 1% /dev/shm

Check, in the output of those commands, that the size of the root partition (/dev/root) is close the the size of your SD (Here above, I have IUsed =~ 32G). If it is not the case, enlarge it with:

sudo raspi-config

7 Advanced Options > A1 Expand Filesystem 


If the size of the root partition is maximum, then investigate to find the very large stuff with:

sudo du -xh / | grep -P "G\t"

1,2G /opt/openhab/userdata
1,2G /opt/openhab
1,2G /opt
1,3G /usr
11G /var/lib/docker
11G /var/lib
11G /var
16G /mnt/backup
16G /mnt
29G /

To only have the size of the first level folders, use:

sudo du -xh --max-depth=1 / | grep -P "G\t"

1.2G /opt
1.3G /usr
11G /var
16G /mnt
29G /

Check, in the output of that command, if there as any folder or file which could be cleaned-up.

You can also us this to navigate into your SD:

sudo mount --bind /  /mnt
sudo ncdu -x /mnt

-- /mnt ------------------------
15,1 GiB [##########] /mnt
10,6 GiB [###### ] /var
1,3 GiB [ ] /usr
1,2 GiB [ ] /opt
415,3 MiB [ ] /home
353,3 MiB [ ] /lib
9,3 MiB [ ] /bin

You can navigate in this table (with keys up and down) and open folders (press enter) to see the details of their content. Exit this table by pressing "q".

If by any accident, you don't succeed to delete a large file or folder (especially if located under /media or /mnt), check that it's not on a mounted drive. Auto-mount are usually in /etc/fstab and may only be :

cat /etc/fstab

You can umount all at once with

sudo umount -a -t cifs -l


Regarding packages, You can cleanup some space with:

sudo apt-get autoremove

sudo rm -R /var/cache/

sudo mkdir -p /var/cache/apt/archives/partial
sudo touch /var/cache/apt/archives/lock
sudo chmod 640 /var/cache/apt/archives/lock
sudo apt-get clean


If you are using docker,

you can check the space consumed with:

sudo du -sh /var/lib/docker/overlay2

docker system df

you can cleanup some space with:

docker system prune -a -f

docker system prune --all --volumes --force

docker volume rm $(docker volume ls -qf dangling=true)


If using GitLab, you can cleanup some space with:

sudo gitlab-ctl registry-garbage-collect


Other useful commands:

sudo find / -type f -size +500M -exec ls -lh {} \;

sudo touch /forcefsck ; sudo reboot

sudo resize2fs /dev/mmcblk0p2 ; sudo reboot

After reboot check the resize status with:

systemctl status resize2fs_once.service

If you see the error "Failed to start LSB: Resize the root filesystem to fill partition", you can disable the resize2fs with:

sudo systemctl disable resize2fs_once


What was the issue in my own case: my remote folder for backup was not mounted anymore on /mnt/backup but the backup script run and stored a 16Gb file into the local folder /mnt/backup. I have been able to delete the local backup by commenting the related shared folder in /ect/stab, rebooting and then deleting /mnt/backup.

Et voilà!

Raspberry Pi Run Raspberry Pi Desktop 4 in VMWare

Instead of testings new softwares or configs on my actual RPI, I do it in a VM Machine. Much easier to rollback if I do a mistake. There are many videos on YouTube to explain how to install the Raspberry Pi Desktop in VMWare.

Click to Read More

The ISO image of Raspberry Pi Desktop is available here.

I did create an VM, as illustrated here, with:

  • 4GB Memory
  • 32GB Hard Disk(SCSI)
  • USB 3 .1
  • And everything else "by default"
    • 1 processor
    • NAT Network Adapter
    • ...

I did:

  • a "Graphical Install" of the Raspberry Pi Desktop
  • enable SSH
  • keep the password "raspberry" for the user pi (with auto-login enabled)
  • configure the keyboard for me (Belgian - Azerty)
  • configure to location as Brussels/Belgium
  • install the VMWare-Tools (screen resolution maximized automatically)
  • Create an icon "Desktop Update" to update the packages via: sudo apt-get update && sudo apt-get upgrade -y

And here attached in the resulting VM (a 4.5GB zip file). Download it, unzip and double click the file "Raspberry Pi 4.vmx" to open the VM into your VMWare Workstation.

Et voilà.

Raspberry Pi Create a Plex Media Player with a Raspberry 4

I used to run Rasplex on a RPI 2 to play movies from my Plex Media Server. Unfortunately Rasplex has not been updated to run on a RPI 4. Here is how to build PMP for RPI 4.

Click to Read More

Install an OS on your RPI 4

  1. Download the "Raspberry Pi Imager" here.
  2. Download next the "Raspberry Pi OS (32-bit) with desktop" here (the 64-bit is still only in beta. See here). Unzip the file.
    • This is the smallest image (no extra softwares) with a Desktop (mandatory to display the Plex Media Player GUI)
  3. Install and Run the "Raspberry Pi Imager" to setup the "Raspberry Pi OS" on a micro-SD card.
    • Click on "Choose OS"

    • Select "Use Custom"

    • Pick the .img file "YYYY-MM-DD-raspios-buster-armhf.img" unzipped from the "Raspberry Pi OS (32-bit) with desktop" image.
    • Next Click "Choose SD" and "Write".
    • Once the operation completed, install the micro-SD in your RPI 4 and turn it on. The Raspberry Pi Desktop will appear after some automatic reboots. Follow the setup of the Welcome screen. Steps are:
      • Setup the Country (use Page up and Page down in the Country Combo to scroll faster)
      • Change the Password of the user 'pi'. ATTENTION: the keyboard layout is most probably not the right one. Untick the "Hide characters" option to check what you type!
      • Set Up Screen
      • Select Wireless Network (You can skip this step if the RPI is connected via ethernet). Again, untick the "Hide characters" option to check what you type!
      • Update Software
      • Click "Restart" on the last step "Setup Complete"

Configure your OS

Open a "Terminal" :

First, type this command in the Terminal to check your IP address:


Type next this command to configure the os:

sudo raspi-config

Among other:

  • Configure your keyboard if required via "4 Localisation Options" > "change keyboard layout"
    • If your keyboard is not in the list, use the Generic 100x-Key PC corresponding to your layout. Look the picture of this wiki page for more details.
    • You can possibly also find more info about your keyboard here.
  • Enable SSH via "5 Interfacing Options" > "P2 SSH"
  • Give at least 512MB or more to your GPU via "7 Advanced Options" > "Memory Split" (I did set 512. Using 1024 result in a black screen after reboot)
  • I gave the whole micro-SD card storage for the OS via "7 Advanced Options" > A1 Expand File System"
  • I set the audio output on the HDMI port via "7 Advanced Options" > A4 Audio"
  • NB.: I don't use the 4Kp60 HDMI, but it can be configured via "7 Advanced Options" > AA Pi 4 Video Output"
  • Finally, reboot to be sure that it still work.
    • If you have an issue, wait for 3 minutes and proceed with the next step here under.


You can now open a SSH console from your PC (E.g: using PuTTY) to connect on the IP address found previously and login with the user 'pi' and the password you introduced during the installation.

You will possibly get a PuTTY Security Alert because of the ssh key fingerprint... Accept if you are sure that you are connecting safely to your RPI.

If it seems that your RPI didn't reboot properly and you are not able to connect using SSH after a moment, they you probably have to redo to whole setup from scratch and try other configuration options within raspi-config

If it seems that your RPI didn't reboot properly and you are able to connect via SSH, redo the configuration with the command sudo raspi-config (try to reset the "Memory Split" to 64 if you did change it).

If you want to be sure that your OS is up-to-date, with the very latest fixes, type the following commands:

sudo apt-get update
sudo apt-get full-upgrade

And finally disable the screen sleep with the command

sudo sed -i 's/#xserver-command=X.*/xserver-command=X -s 0 dpms/g' /etc/lightdm/lightdm.conf

Build PMP for your RPI 4

Use now the SSH console (to be able to copy/paste from here) to execute this:

sudo apt-get install -y autoconf automake libtool libharfbuzz-dev libfreetype6-dev libfontconfig1-dev libx11-dev libxrandr-dev libvdpau-dev libva-dev mesa-common-dev libegl1-mesa-dev yasm libasound2-dev libpulse-dev libuchardet-dev zlib1g-dev libfribidi-dev git libgnutls28-dev libgl1-mesa-dev libsdl2-dev cmake python3 python python-minimal git mpv libmpv-dev

Then these 3 commands:

wget https://github.com/koendv/qt5-opengl-raspberrypi/releases/download/v5.12.5-1/qt5-opengl-dev_5.12.5_armhf.deb 
sudo apt-get install -y ./qt5-opengl-dev_5.12.5_armhf.deb
rm qt5-opengl-dev_5.12.5_armhf.deb

And finally these:

mkdir ~/pmp
cd ~/pmp
git clone git://github.com/plexinc/plex-media-player
cd plex-media-player/
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Debug -DQTROOT=/usr/lib/qt5.12/ -DCMAKE_INSTALL_PREFIX=/usr/local/ ..
make -j4
sudo make install

Now, PMP can be run. Go back to the Raspberry Pi Desktop, and type this command in a Terminal:

plexmediaplayer --fullscreen --tv &

In my case, the option 'tv' is not convenient (I can't see enough on the screen)...

You will have to Sign In via the link page of Plex.tv and next configure Plex Media Player.

Configure PMP to launch at boot

Back into you SSH Console, on your PC, create a new user 'plex' with a password:

sudo adduser plex
sudo adduser --disabled-password plex
sudo passwd -d plex

Login as 'plex' in your RPI desktop to run once PMP via a Terminal (Without this step, it will not be displayed full screen after an autologin):

plexmediaplayer --fullscreen --tv &

Configure the user 'plex' to autologin with a desktop session named 'plex':

sudo sed -i 's/#*user-session=.*/user-session=plex/g' /etc/lightdm/lightdm.conf
sudo sed -i 's/#*autologin-user=.*/autologin-user=plex/g' /etc/lightdm/lightdm.conf
sudo sed -i 's/#*autologin-user-timeout=.*/autologin-user-timeout=delay/g' /etc/lightdm/lightdm.conf

Create the 'plex' desktop:

sudo nano /usr/share/xsessions/plex.desktop

and paste into it:

[Desktop Entry]Name=Plex
Comment=Plex Media Player

And now reboot ! (It can take 3 long minutes !!):

sudo reboot

If there is a configuration issue with the desktop, edit the config via a SSH console and restart lightDM (the Desktop Manager):

sudo service lightdm restart

Tips: I had no issue with getting Plex Media Player in fullscreen but here are notes in case I would have to resize it:

sudo apt-get install -y xdotool
export DISPLAY=':0.0'
xdotool search --onlyvisible --maxdepth 1 ""
xdotool windowmove {window_id} {posx} {posy} windowsize {window_num} {sizex} {sizey}


This is based on a post of Stueh on Plex forum (see here)


If you did configure Plex Media Player on a PC Screen and move next on TV Screen, it will most probably not fit that screen et the resolution will possibly not be correct. In that case, here is how I proceed:

  • Log on your RPI using any SSH console on your mobile or Tablet (I presume that your PC is not next to your TV). I am using "RaspController" on Android
  • Edit the desktop to force an error. Hence, you will fallback on the default Desktop. Type in you SSL console : sudo nano /usr/shared/xsession/plex.desktop
    • Ex.: modify this line to define an invalid path: Exec=xxx/usr/local/bin/plexmediaplayer
  • Now, restart LightDM
    • Either type this in your SSH console: sudo service lightdm restart
    • Or CTRL-ALT-Backspace on the keyboard of your RPI.
  • You will get an error message because 'xxx/usr/local/bin/plexmediaplayer' does not exist and next get a prompt to login.
  • Login as 'pi' 
  • Now, open the Start menu > Preferences > Raspberry Pi Configuration > Display (or Interfaces). If you don't see the 'Start menu' because it is out of the screen, press the 'Windows' key on your Keyboard.

  • Next, change the resolution to fit the limitation of your TV:
    • 480p = DVD, old TV 720 x 480 pixels, format 16/9.
    • 720p = HD Ready, 1280 x 720 pixels, format 16/9.
    • 1080p = Full HD, 1920 x 1080 pixels, format 16/9.
    • 2160p, UHDTV1, 3840 x 2160 pixels, format 16/9 (a.ka. UHD-4K or 4K).
    • 4320p, UHDTV2, 7680 x 4320 pixels, format 16/9 (a.k.a UHD-8K or 8K).
  • Then, open Plex Media Player (Start Menu > ...) and configure it in TV mode. If it does not fit the TV Screen, reduce the resolution.
  • Finally, log off (or restrat lightDM with CTRL-ALT-BACKSPACE) and login as 'plex' to also run Plex Media Player and be sure it's also well configured.
  • Ho, yes, sure: edit again the plex.desktop to remove the xxx in the path of the EXEC setting and reboot.


Synology Shrink a SHR Volume and remove disks from a Synology

I wanted to try this since years... I finally did it successfully in a virtual Synology with an array of 5 disks in a single volume using btrfs (See here for VM and btfrs).

Click to Read More

This is a summary of my attempts. It is based on various posts found on the web:

  • https://superuser.com/questions/834100/shrink-raid-by-removing-a-disk
  • https://unix.stackexchange.com/questions/67702/how-to-reduce-volume-group-size-in-lvm#67707
  • https://blog.reboost.net/manually-removing-a-disk-from-a-synology-raid/

Notice that xfs File System only supports "extend" and not "reduce". So, I only tried with etx4 and btrfs.

Although I used a DSM with a video station, a photo station, the web station and wordpress, this was not a "real case" (most of the data were still on the first sectors of the disks). So, I would really not recommend to do this on a real NAS !!!


Open a SSH console and enter root mode (sudo -i) to execute the commands here after.

To identify which process is accessing a volume, we possibly need lsof (only if umount fails)

Install OPKG : See https://www.beatificabytes.be/use-opkg-instead-of-ipkg-on-synology/

Install lsof: /opt/bin/opkg install lsof

Layout of the Physical Volume/Volume Group/ Logical Volumes :

Find the Filesytem of /volume1:

df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/md0        2.3G 1016M  1.2G  46% /
none            2.0G     0  2.0G   0% /dev
/tmp            2.0G  536K  2.0G   1% /tmp
/run            2.0G  3.2M  2.0G   1% /run
/dev/shm        2.0G  4.0K  2.0G   1% /dev/shm
none            4.0K     0  4.0K   0% /sys/fs/cgroup
cgmfs           100K     0  100K   0% /run/cgmanager/fs
/dev/vg1000/lv   14G  3.2G  9.9G  25% /volume1

  • Show Physical Volume: pvdisplay
  • Show Volume Group: vgdisplay
  • Show Logical Volume: lvdisplay
  • Show Disks: fdisk -l

Check if one can umount the volume1 :

umount /dev/vg1000/lv

umount: /volume1: target is busy
       (In some cases useful info about processes that
        use the device is found by lsof(8) or fuser(1).)

Stop all services :

synopkg onoffall stop

/usr/syno/etc.defaults/rc.sysv/S80samba.sh stop

/usr/syno/etc.defaults/rc.sysv/S83nfsd.sh stop

/usr/syno/etc.defaults/rc.sysv/pgsql.sh stop

/usr/syno/etc.defaults/rc.sysv/synomount.sh stop

check which daemons are still using volume1 :

/opt/bin/lsof | grep volume1

COMMAND    PID  TID     USER  FD        TYPE                          DEVICE SIZE/OFF       NODE NAME
s2s_daemo 10868         root    8u      REG               0,30    11264        608 /volume1/@S2S/event.sqlite
synologan  8368         root  3u        REG               0,30       3072        654 /volume1/@database/synologan/alert.sqlite
synoindex  8570         root  mem       REG               0,28                  7510 /volume1/@appstore/PhotoStation/usr/lib/libprotobuf-lite.so (path dev=0,30)
synoindex  8570         root  mem       REG               0,28                 30143 /volume1/@appstore/VideoStation/lib/libdtvrpc.so (path dev=0,30)
lsof       8585         root  txt       REG               0,30     147560      32161 /volume1/@entware-ng/opt/bin/lsof

Kill those daemons :

initctl list | grep synoindex

synoindexcheckindexbit stop/waiting
synoindexd start/running, process 11993

killall synoindexd

initctl list | grep synologan

synologand start/running, process 8368

killall synologand

This is not working… synologand  restart immediately ☹

chmod u-x /usr/syno/sbin/synologand

killall synologand 

killall s2s_daemon

Shrink the ext2 or ext4 Filesystem :

Only do the steps here under if using ext2 or ext4 instead of btfrs

Resize the File System :

umount -d /dev/vg1000/lv

e2fsck -f /dev/vg1000/lv

e2fsck 1.42.6 (21-Sep-2012)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
/lost+found not found. Create<y>? yes
Pass 4: Checking reference counts
Pass 5: Checking group summary information

1.42.6-23739: ***** FILE SYSTEM WAS MODIFIED *****
1.42.6-23739: 30742/889440 files (0.7% non-contiguous), 734048/3553280 blocks

resize2fs -M /dev/vg1000/lv

resize2fs 1.42.6 (21-Sep-2012)
Resizing the filesystem on /dev/vg1000/lv to 702838 (4k) blocks.
The filesystem on /dev/vg1000/lv is now 702838 blocks long.

If you see the error message here under, you possibly have another file system than ext2 or ext4 (E.g.: btfrs, ...):

resize2fs: Bad magic number in super-block while trying to open /dev/vg1000/lv
Couldn't find valid filesystem superblock.

If you have this error message although having ext2 or ext4, try: lvm lvchange --refresh /dev/vg1000/lv

Check the results :

mount /dev/vg1000/lv /volume1
df -h

Filesystem Size Used Avail Use% Mounted on
/dev/md0 2.3G 968M 1.3G 44% /
none 2.0G 0 2.0G 0% /dev
/tmp 2.0G 512K 2.0G 1% /tmp
/run 2.0G 3.0M 2.0G 1% /run
/dev/shm 2.0G 4.0K 2.0G 1% /dev/shm
none 4.0K 0 4.0K 0% /sys/fs/cgroup
cgmfs 100K 0 100K 0% /run/cgmanager/fs
/dev/vg1000/lv 2.6G 2.5G 0 100% /volume1

Resize the Logical Volume :

Resize the logical volume a bit larger than the file system (See the outcome of df -h above)

umount /dev/vg1000/lv
lvm lvreduce -L 2.7G /dev/vg1000/lv

Rounding size to boundary between physical extents: 2.70 GiB
WARNING: Reducing active logical volume to 2.70 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce volume_1? [y/n]: y
Size of logical volume vg1/volume_1 changed from 13.55 GiB (3470 extents) to 2.70 GiB (692 extents).
Logical volume volume_1 successfully resized.


Shrink a BTRFS File System :

Only do the steps here under if using btfrs

Resize the File System :

btrfs filesystem resize 2.7G /volume1

You can restore max size if required: btrfs filesystem resize max /volume1

df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/vg1000/lv  2.6G 2.5G  1.4G  71% /volume1

Resize the Logical Volume:

umount -d /dev/vg1000/lv

lvm lvreduce -L 2.7G /dev/vg1000/lv


Next steps :

The steps here under are both for ext2/ext4 and btfrs

Resize the Physical Volume :

Look for the device and if blocks must be moved:

pvdisplay -C

PV VG Fmt Attr PSize PFree
/dev/md2 vg1 lvm2 a-- 13.57g 10.85g

pvs -v --segments /dev/md2

    Using physical volume(s) on command line.
   Wiping cache of LVM-capable devices
PV         VG     Fmt  Attr PSize  PFree   Start SSize LV   Start Type   PE Ranges
/dev/md2   vg1000 lvm2 a--  14.00g 440.00m     0  3473 lv       0 linear /dev/md2:0-3472
/dev/md2   vg1000 lvm2 a--  14.00g 440.00m  3473   110          0 free

If there is a bloc trailing after the "free" part (I had not), use:

lvm pvmove --alloc anywhere /dev/md2:xxx-xxx


Resize the device a bit larger than the logical volume. If you don't use a sufficient size, you will get an error message:

pvresize --setphysicalvolumesize 2.7G /dev/md2

/dev/md2: cannot resize to 691 extents as 695 are allocated.
0 physical volume(s) resized / 1 physical volume(s) not resized

pvresize --setphysicalvolumesize 2.8G /dev/md2

Physical volume "/dev/md2" changed
1 physical volume(s) resized / 0 physical volume(s) not resized


Resize the array to use less disks:

Reduce the array to use 3 disks (-n3)

mdadm --grow -n3 /dev/md2

mdadm: this change will reduce the size of the array.
      use --grow --array-size first to truncate array.
      e.g. mdadm --grow /dev/md2 --array-size 7114624

You have first to reduce the array size.

mdadm --grow /dev/md2 --array-size 7114624

mdadm --grow -n3 /dev/md2 --backup-file /root/mdam.md2.backup &


Monitor the progress of the resizing with:

cat /proc/mdstat

Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [raidF1]md2 : active raid5 sdak5[4] sdaj5[3] sdai5[2] sdah5[1] sdag5[0]7114624 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU][======>..............] reshape = 31.7% (1129600/3557312) finish=0.3min speed=112960K/sec

md1 : active raid1 sdak2[4] sdaj2[3] sdai2[2] sdah2[1] sdag2[0]2097088 blocks [12/5] [UUUUU_______]
md0 : active raid1 sdak1[4] sdaj1[3] sdag1[0] sdah1[1] sdai1[2]2490176 blocks [12/5] [UUUUU_______]
unused devices: <none>

This can take a lot of time, but you can continue (I did wait ;) )


pvresize /dev/md2

Physical volume "/dev/md2" changed
1 physical volume(s) resized / 0 physical volume(s) not resized

lvextend -l 100%FREE /dev/vg1000/lv

Size of logical volume vg1/volume_1 changed from 2.70 GiB (692 extents) to 4.07 GiB (1041 extents).
Logical volume volume_1 successfully resized.

for btrfs:

btrfs filesystem resize max /volume1

for ext2/ext4:

e2fsck -f /dev/vg1000/lv

e2fsck 1.42.6 (21-Sep-2012)
Pass 1: Checking inodes, blocks, and sizes

Running additional passes to resolve blocks claimed by more than one inode...
Pass 1B: Rescanning for multiply-claimed blocks
Multiply-claimed block(s) in inode 13: 9221
Pass 1C: Scanning directories for inodes with multiply-claimed blocks
Pass 1D: Reconciling multiply-claimed blocks
(There are 1 inodes containing multiply-claimed blocks.)

File /@tmp (inode #13, mod time Sat May 23 23:00:14 2020)
has 1 multiply-claimed block(s), shared with 0 file(s):
Multiply-claimed blocks already reassigned or cloned.

Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
1.42.6-23739: 30742/179520 files (0.7% non-contiguous), 685397/720896 blocks

Hope that no nodes are corrupted. Otherwise... well... accept to fix them.

resize2fs /dev/vg1000/lv

resize2fs 1.42.6 (21-Sep-2012)
Resizing the filesystem on /dev/vg1/volume_1 to 1065984 (4k) blocks.
The filesystem on /dev/vg1/volume_1 is now 1065984 blocks long.

mount /dev/vg1000/lv /volume1

Restart services:

/usr/syno/etc.defaults/rc.sysv/S80samba.sh start

/usr/syno/etc.defaults/rc.sysv/S83nfsd.sh start

/usr/syno/etc.defaults/rc.sysv/pgsql.sh start

/usr/syno/etc.defaults/rc.sysv/synomount.sh start


synopkg onoffall start


Remove the new  spare disks from the volume

mdadm --detail --scan

ARRAY /dev/md0 metadata=0.90 UUID=3b122d95:7efea8ff:3017a5a8:c86610be

ARRAY /dev/md1 metadata=0.90 UUID=bd288153:d00708bf:3017a5a8:c86610be

ARRAY /dev/md2 metadata=1.2 spares=2 name=DS3617_62:2 UUID=875ad2d6:956306b7:8c7ba96b:4287f6e6

mdadm --detail /dev/md2

       Version : 1.2
Creation Time : Sat May 23 14:00:02 2020
    Raid Level : raid5
    Array Size : 7114624 (6.79 GiB 7.29 GB)
Used Dev Size : 3557312 (3.39 GiB 3.64 GB)
  Raid Devices : 3
Total Devices : 5
   Persistence : Superblock is persistent

    Update Time : Sat May 23 18:54:30 2020
         State : clean
Active Devices : 3
Working Devices : 5
Failed Devices : 0
Spare Devices : 2

         Layout : left-symmetric
    Chunk Size : 64K

           Name : DS3617_62:2  (local to host DS3617_62)
          UUID : 875ad2d6:956306b7:8c7ba96b:4287f6e6
        Events : 56

    Number   Major   Minor   RaidDevice State
      0       8        5        0      active sync   /dev/sda5
      1       8       37        1      active sync   /dev/sdc5
      2       8       53        2      active sync   /dev/sdd5
      3       8       69        -      spare   /dev/sde5
      4       8       85        -      spare   /dev/sdf5

Here above, we see that sde5 and sdf5 are unused


mdadm --fail /dev/md2 /dev/sde5

mdadm: set /dev/sde5 faulty in /dev/md2

mdadm --fail /dev/md2 /dev/sdf5

mdadm: set /dev/sdf5 faulty in /dev/md2

mdadm --remove /dev/md2 /dev/sde5

mdadm: hot removed /dev/sde5 from /dev/md2

mdadm --remove /dev/md2 /dev/sdf5

mdadm: hot removed /dev/sdf5 from /dev/md2


Et voilà.

Synology Add Support for SHR on Synology DS3617xs

I wanted to test a procedure to shrink a SHR volume on a virtual Synology DS3617. Unfortunately, SHR is not an available option on the high end models of Synology. But it can be enabled easily ;)

Click to Read More

DS3617xs is a model where SHR is not enabled:


To enable it:

  1. Open a SSH console and enter root mode.
  2. Edit the file  /etc.defaults/synoinfo.conf
  3. At the end, you should find: supportraidgroup="yes"
  4. Comment that line with a #
  5. Next to it, add a new line with: support_syno_hybrid_raid="yes"
  6. Reboot your Synology

You can use "vi" to edit the file: sudo vi /etc.defaults/synoinfo.conf,

  • Press i or the insert key to make your modifications, then "Esc" to end the modifications.
  • After that type :x! to save and exit. Ot :q! to exit without saving.

Et voilà, your DS3617xs offers now the option for SHR

Tips VMWare Workstation not compatible with Windows 10

Starting a VM this morning, I got a new message "VMware Workstation and Device/Credential Guard are not compatible". To be able to run my VM, I had to disable this Credential Guard.

Click to Read More

Credential Guard uses virtualization to store credentials in protected containers separate from the OS. As a result, the information Credential Guard protects is safe even if malware or some other malicious attack penetrates an organization's network.

But it prevents VMWare to run VM's.

To disable it, copy this script in a file named "disableCG.ps1" in your personal home folder C:\Users\<Your Name>\

Run next a PowerShell as Administrator:

Pay Attention that this will reboot automatically your PC !!

In this PowerShell, execute: cd ~

Next execute : .\disableCG.ps1 -Disable -AutoReboot

You will see errors displayed in Red in the PowerShell. This won't be a problem. And after a minute, the PC will reboot.

During the reboot, you will be prompted to confirm that you really want to disable the Windows Defender Credential Guard. Press the Windows Key or F3 to confirm.


Other options : https://windowsreport.com/disable-credential-guard-windows-10/

Ex. Execute in a PowerShell run as Administrator: bcdedit /set hypervisorlaunchtype off


I also had to remove "Guarded Host" and "Hyper -V" via the Control Panel > Programs > Turn Windows features on or off

But now, Docker does not run anymore on my PC as it needs Hyper-V :(

SmartHome Philips Hue lights Bulbs and Accessories become unreachable

Regularly, my Philips Hue lights and accessories do not respond anymore. Looking into the Philips Hue App, they appear as "Unreachable" (no link). The solution was to avoid WiFi interference!

Click to Read More

In French, the message displayed by the App, for the Lights and accessories, is "impossible d'établir le lien".

If your Philips Hue lights aren't responding, maybe it's time to ...


Notice that each time, a few bulbs and accessories were still connected and the App was perfectly able to connect onto the Bridge, both via Internet and via my local Network. Notice also that I have many Philips Hue Light Bulbs, Sensors and Dimmer Switches in the house (less than 50, which is the theoretical maximum for a Philips Hue Bridge) as well as a few Tradfri Bulbs in the corridors.

I really spent hours to investigate this issue which occurred once every few months ...

  • Unplug the power supply of the Philips Bridge for 30 sec.
  • Switch off all the lights for 30 sec.
  • Remove the Bulbs from their sockets.
  • Press the 4 buttons of the remotes (Philips Hue Dimmer Switch) all together for a few seconds (until the led start to blink red/green).
  • Press both the On and Off buttons of the remote to reset the Bulbs.
  • Turn on/off the lights quickly several times (and do an incantation for Apollo).
  • Delete and Re-add again the lights and accessories within the App.
  • Go through the whole FAQ of Philips Hue.
  • Drink a bottle of wine and cry alone in my sofa.
  • etc...

I was always finally switching off all electric devices which were possibly disrupting the Zigbee signals : my routers, my wifi access points, my other Bridges (Tahoma Somfy, Z-Wave, ...) ... and even powering off the whole house... This extreme action was solving the problem ! But impossible to conclude what was the precise root cause.

Today, the problem occurred again. After various unsuccessful attempts (those mentioned above),  I read on a blog that the quality of the ethernet connection between the Philips Hue Bridge and Internet matters ?!? And I realized that my Bridge was plugged into a Devolo Powerline Adapter (Ethernet via Power Sockets). I also remember that in the past, unplugging and replugging that Devolo Powerline Adapter was an action I did and which solved the problem (but I actually did this to restart the various Bridges and WiFi access points connected onto it).

So, I moved the Philips Hue devices from that Adapter into the main Ethernet Router and boom, it worked !

Et voilà ? Really not sure. The ethernet connection is only for the Bridge to have access on a Wifi Access Point and be able to connect with the mobile App... The bulbs and the Bridge are connected via Zigbee. So, there  must be another reason hidden behind this (fake) "solution".

Note that the Phillips Hue Light Bulbs, even though they are Zigbee, do not act as repeaters for anything except other Light Bulbs on the same Hue bridge if they are connected to the Hue bridge (They use actually a "Zigbee Light Link" protocol instead of the regular Zigbee).

As I noticed that the disconnected Bulbs are often the Tradfri ones and the Philips Hue far from the Bridge, I thought that the problem was possibly more with the Tradfri light bulbs not receiving/repeating properly the signal for the Philips Hue light bulbs ? Two possible options:

  • Replace the cheap Tradfri light bulbs with expensive Philips Hue light bulbs. I will do so soon or later...
  • Investigate why receiving/repeating the ZigBee signal could fail... I can start with this.

It's often mentioned on the web that ZigBee can suffer for WiFi interferences. It shares the same 2.4GHz wireless band as WiFi routers and overlaps by default with the Wifi channel 11 (https://statusq.org/archives/2018/01/09/8435/). And indeed, moving the Philips Hue Bridge or Turning On/Off all Wifi Devices in the house used to solve, at least temporarily, the problem.

Ex.: Zigbee channels 21 to 24 overlaps with WiFi channel 11 as illustrated bellow. 

A first obvious solution  is to disable the WiFi 2.4GHz band and use only the 5GHz band for the WiFi Devices at home. But not all of them support 5GHz...

Another solution is to change the channel used by the Philips Hue Bridge  to use a ZigBee channel having less conflict with your WiFi (All lights must be powered on). Do the change via Philips Hue App's settings > Hue Bridges > touch the "i" of the Bridge to update > ZibBee channel change > Change Channel.

It will take about 30 seconds, but the Hue system will change the channel to another one automatically. Once done, the lights should all come back online (And indeed, this did the trick once for me too, without doing any other action). If they don’t, turn them on and off again at the main light switch/plug socket. Possible Zigbee channels are 11, 15, 20 and 25

Philips Hue Zigbee channel

Also you can try to move the Philips Hue Bridge to another location, not too close of the WiFi access points and in central location regarding the various ZigBee devices. This is what I did by connecting the Bridge directly on the Router (So the solution was not the improvement of the ethernet connection quality, but most probably a lower WiFi interference next to that Router).

Notice that this won't update the channel used by the Tradfri lights! As explained on Reddit by Erik1971, you can try, after changing the Hue System channel, to power cycle the Tradfri lights (make sure they are not powered for at least 1 minute). This should trigger the Tradfri lights to scan over the channels to join the network again. Best way to do this is to power off all Tradfri lights and keep the Hue Lights and Bridge powered and then one by one power on the Tradfri lights (to prevent that the Tradfri Lights see the other Tradfri lights on the wrong channel and rejoin on the wrong channel).

So, for the time being, my conclusion is that bulbs and accessories became unreachable due to (many?) new devices connecting on the WiFi or WiFi Access Points changing automatically their channels (This can be checked with an App like Wifi Analyzer).