Debian 9: Backlight Brightness

bootbrightnessdebianmonitorssystem-installation

I've just installed a fresh new Debian 9 with LXDE into an ACER AMD Notebook and everything seems to be working fine, except for the backlight brightness. During the boot, it happens the following:

several messages and errors appear

[FAILED] Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0.
See 'systemctl status systemd-backlight@backlight:acpi_video0.service' for details.
Starting Load/Save Screen Backlight Brightness of backlight:radeon_bl0
...
[ OK ] Started Load/Save Screen Backlight Brightness of backlight:radeon_bl0

often backlight brightness is reset to max

In order to set the backlight brightness to an acceptable level, the best solution so far seems to be opening a terminal and typing the command line below as soon as Debian initialize:

tee /sys/class/backlight/radeon_bl0/brightness <<< 15

Questions

How to avoid the backlight brightness being reset to max during the boot?
How to set shortcuts to the backlight brightness (ex: [Fn] + ←/→)?

Debug

root@debian:~# dmesg | grep -i "error\|firmware\|backlight"
[    1.049855] pci 0000:01:00.0: [Firmware Bug]: disabling VPD access (can't determine size of non-standard VPD format)
[    7.729996] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro
[   12.960474] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/PALM_pfp.bin
[   13.017938] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/PALM_me.bin
[   13.043827] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/SUMO_rlc.bin
[   13.161157] radeon 0000:00:01.0: firmware: direct-loading firmware radeon/SUMO_uvd.bin
[   13.897112] [drm] radeon atom DIG backlight initialized

root@debian:~# systemctl status systemd-backlight@backlight:acpi_video0.service
● systemd-backlight@backlight:acpi_video0.service - Load/Save Screen Backlight Brightness of backlight:acpi_video0
   Loaded: loaded (/lib/systemd/system/systemd-backlight@.service; static; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sat 2018-06-16 06:37:19 -03; 29min ago
     Docs: man:systemd-backlight@.service(8)
  Process: 411 ExecStart=/lib/systemd/systemd-backlight load backlight:acpi_video0 (code=exited, status=1/FAILURE)
 Main PID: 411 (code=exited, status=1/FAILURE)

Jun 16 06:37:19 debian systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:acpi_video0...
Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Main process exited, code=exited, status=1/FAILURE
Jun 16 06:37:19 debian systemd[1]: Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0.
Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Unit entered failed state.
Jun 16 06:37:19 debian systemd[1]: systemd-backlight@backlight:acpi_video0.service: Failed with result 'exit-code'.

Hardware Specifications
Notebook Aspire E1-421-0622 | product details

AMD 2 Core™ Processor E1-1200 (1.4 GHz) 1MB Cache 64-bit Processing
AMD Radeon HD 7310 Graphics Controller
2Gb DDR3 SDRAM Memory
256MB shared video memory

Debian Strech
debian-9.4.0-amd64-netinst.iso

Small CDs
AMD64 processor architecture
Non-free package firmware-amd-graphics installed
radeon kernel modesetting for R600 or later requires firmware-amd-graphics
Software selection
( ) Debian desktop environment
( ) … GNOME
( ) … Xfce
( ) … KDE
( ) … Cinnamon
( ) … MATE
(X) … LXDE
( ) web server
(X) print server
( ) SSH server
(X) standard system utilities

Best Answer

Your system seems to have two interfaces for backlight control: backlight:acpi_video0 and backlight:radeon_bl0. And apparently the ACPI interface does not work, and/or causes problems when used together with the Radeon-specific interface.

Since the Radeon-specific interface seems to work fine, I'd try telling systemd to stop using the ACPI backlight interface first:

systemctl mask systemd-backlight@backlight:acpi_video0.service

If necessary, this can be undone with:

systemctl unmask systemd-backlight@backlight:acpi_video0.service

If this does not help, further investigation is needed.

With journalctl -xb you should be able to see a quite verbose version of messages for the current boot only. By default, persistent storage of systemd journal is not enabled in Debian 9, but it's quite easy to enable: just run mkdir /var/log/journal as root. Then, starting from next boot, the journal will be stored persistently and you will be able to e.g. view the log of the previous boot from startup to shutdown with journalctl -xb -1. The oldest logs will eventually be automatically purged, controlled by journald's configurable criteria for available disk space.

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Why x0vncserver is not starting at boot

As x0vncserver will only start after xsession, and as mine is an LXDE environment, the easier way is to create a script.sh file like following

#!/bin/bash
x0vncserver -display :0 -rfbport 5900 -passwordfile ~/.vnc/passwd

and make it executable by sudo chmod +x script.sh and add a line in ~/.config/lxsession/LXDE/autostart file like following

path_to_the_script_file/script.sh

and the x0vncserver starts as my LXDE desktop session starts and that's what I need.

Debian – Failed to start MariaDB database server after upgrade to debian 9

In the tutorial you should install mariadb-server in place of mysql-server. I've got the same problem on DEBIAN 9 install and these command worked for me :

sudo apt purge mysql*
sudo apt purge mariadb*
sudo apt autoremove
sudo apt autoclean

Check if still something in the system :

dpkg -l | grep -e mysql -e mariadb

if the list is empty then install mariadb server :

sudo apt install mariadb-server

Now try to check status on stop and start the database :

Status after install :

sudo systemctl status mysql.service
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2018-03-21 16:08:49 CET; 2min 1s ago
 Main PID: 15699 (mysqld)
   Status: "Taking your SQL requests now..."
   CGroup: /system.slice/mariadb.service
           └─15699 /usr/sbin/mysqld

.../..

Check the PID :

sudo more /var/run/mysqld/mysqld.pid 
15699

Stop the database :

sudo systemctl stop mysql.service
sudo systemctl status mysql.service
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Wed 2018-03-21 16:14:35 CET; 1s ago
 Main PID: 15699 (code=exited, status=0/SUCCESS)
   Status: "MariaDB server is down"

.../...

You could check the PID file is not present as well

sudo more /var/run/mysqld/mysqld.pid 
more: stat on /var/run/mysqld/mysqld.pid: No file or folder

Start the database :

sudo systemctl start mysql.service
sudo systemctl status mysql.service
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2018-03-21 16:14:54 CET; 3s ago
  Process: 15911 ExecStartPost=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 15908 ExecStartPost=/etc/mysql/debian-start (code=exited, status=0/SUCCESS)
  Process: 15791 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_S
  Process: 15787 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 15784 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
 Main PID: 15881 (mysqld)
   Status: "Taking your SQL requests now..."
    Tasks: 26 (limit: 4915)
   CGroup: /system.slice/mariadb.service
           └─15881 /usr/sbin/mysqld

You could check the PID file it should be present. May help on a empty database. If there is something in the database you should do a backup first.

Best Answer

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