Opening GPIO: opening 'export': Permission denied [errno 13]

Comments

• Repetier

  November 2022

  Access is file based from user repetierserver, so run
  ls -l /sys/class/gpio/gpiochip0/
  to see which group is allowed to access the pins. For pi it is group gpio which is no problem because repetierserver is member of that group. If your linux uses a different group for this you might need to add repetierserver to that group to get permission. 
• laurentgluck

  November 2022

  Dear,
  Thanks for your help.
  With ls -l /sys/class/gpio/gpiochip0/ I have this: 
  

  laurent@rockpi-4b:~$ ls -l /sys/class/gpio/gpiochip0/

  total 0

  -r--r--r-- 1 root root 4096 Nov  9 17:38 base

  lrwxrwxrwx 1 root root    0 Nov  9 17:38 device -> ../../../ff720000.gpio

  -r--r--r-- 1 root root 4096 Nov  9 17:38 label

  -r--r--r-- 1 root root 4096 Nov  9 17:38 ngpio

  drwxr-xr-x 2 root root    0 Nov  9 17:31 power

  lrwxrwxrwx 1 root root    0 Nov  9 17:31 subsystem -> ../../../../../../class/gpio

  -rw-r--r-- 1 root root 4096 Nov  9 17:31 uevent

  
  I also add repetierserver in gpio and laurent groupe but without any success, same error "Opening GPIO: opening 'export': Permission denied [errno 13]".
  Hereunder the groupe list.
  

  laurent:x:1000:repetierserver

  polkitd:x:999:

  ssl-cert:x:122:

  xrdp:x:123:

  gpio:x:1001:laurent,repetierserver

  
  

  Regards

  Laurent

  

  

  
  

   
• Repetier

  November 2022

  On a pi it looks like this:
  

  ls -l /sys/class/gpio/gpiochip0/

  total 0

  -r--r--r-- 1 root gpio 4096 Sep 10 07:57 base

  lrwxrwxrwx 1 root gpio    0 Sep 10 07:57 device -> ../../../fe200000.gpio

  -r--r--r-- 1 root gpio 4096 Sep 10 07:57 label

  -r--r--r-- 1 root gpio 4096 Sep 10 07:57 ngpio

  drwxrwxr-x 2 root gpio    0 Sep 10 07:57 power

  lrwxrwxrwx 1 root gpio    0 Sep 10 07:57 subsystem -> ../../../../../../class/gpio

  -rw-rw-r-- 1 root gpio 4096 Sep 10 07:57 uevent

  
  you see the second name in ls -l output is the group which is here gpio. On your linux these files belong to group root, which is why you get permission denied. You can test if assigning group root to repetierserver helps here. But as you see the group user has not write permissions to the files so I think it will not help. You would need to start server as user root to get access here or find out how to change group and group permissions.
  
  You can do so in service but note that updating server will overwrite your changes and you have to repeat them. The service file is
  /lib/systemd/system/RepetierServer.service
  and contains this:
  

  [Unit]

  Description=Repetier-Server 3D Printer Server

  After=network.target

  
  

  [Service]

  Type=forking

  PermissionsStartOnly=true

  LimitNICE=-20

  Nice=-20

  KillMode=process

  User=repetierserver

  Environment="LC_ALL=C"

  ExecStartPre=/bin/mkdir -p /var/lib/Repetier-Server

  ExecStartPre=/bin/chown -R repetierserver /var/lib/Repetier-Server

  ExecStart=/usr/local/Repetier-Server/bin/RepetierServer -c /usr/local/Repetier-Server/etc/RepetierServer.xml --daemon

  Restart=on-failure

  RestartSec=0

  TasksMax=infinity

  
  

  [Install]

  WantedBy=multi-user.target

  
  
  You need to change User and also the chown command to use root instead of repetierserver than server runs as root after service restart:
  sudo systemctl daemon-reload
  sudo service RepetierServer restart
  
  

  
  
  
• laurentgluck

  November 2022

  Dear,
  
  Thanks for your help, the error message disappeared by following your instructions, thank you for your help.
  
  Question: If during the installation of Armbian, I set the user "PI" from the start, will this save me all these problems?
  
  Many thanks again for your help and responsiveness.
  Regards
  Laurent
  
  
• Repetier

  November 2022

  I don't think that this would have helpered here. pi is not root as well and has nothing to do with user used by server.