Knowledge Base (Posts about display)

Devuan laptop: use external monitor with sound

bgstack15 — Sun, 08 Jun 2025 12:35:00 GMT

I used arandr to set up 2-monitor display after plugging in the HDMI display, and saved the config to ~/.screenlayout/2mon.sh. I then added the pulseaudio command to set the default profile to output audio to the hdmi.

xrandr --output eDP-1 --primary --mode 1920x1080 --pos 0x0 --rotate normal --output DP-1 --off --output HDMI-1 --off --output DP-2 --off --output HDMI-2 --mode 1920x1080 --pos 1920x0 --rotate normal
pacmd set-card-profile 0 output:hdmi-stereo

References

pacmd interactive terminal

Found! Oneliner for nvidia display settings

bgstack15 — Sat, 09 Dec 2023 13:53:30 GMT

tl;dr

I finally found a oneliner method for controlling which monitors are actively used for my NVIDIA graphics card after using it for years. Xrandr doesn't cut it when using nvidia.

nvidia-settings --assign "CurrentMetaMode=DPY-4: nvidia-auto-select @1920x1080 +1920+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}, DPY-1: nvidia-auto-select @1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}"

Of course the exact settings depend on your setup. You need all the contents after the colons, ::, from this command:

$ nvidia-settings -q CurrentMetaMode

  Attribute 'CurrentMetaMode' (pcb-009:0.0): id=50, switchable=no, source=nv-control :: DPY-4: nvidia-auto-select @1920x1080 +1920+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}, DPY-1: nvidia-auto-select @1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}

That's it. I've pondered this ease of use for years, and had actually started an xdotool wrapper but one final Internet search led to this great discovery.

File listings

I of course wrote a script that takes a limited input, "both" or "right" to use those monitors.

files/2023/12/listings/switch-monitors.sh (Source)

#!/bin/sh
# File: switch-monitors.sh
# Location: /usr/local/bin
# Author: bgstack15
# SPDX-License-Identifier: GPL-3.0
# Startdate: 2023-12-05-3 16:15
# Title: Switch monitor config for NVIDIA graphics card
# Purpose: easily switch between 1 monitor and 2 monitors on pcb-009.
# History: attempt 2. The first was attemping to read nvidia-settings -q dpys and parsing enabled/connected, but I didn't know how to use the derived values
# Usage: Called by tray icon
# Reference:
#    https://wiki.archlinux.org/title/NVIDIA#Using_nvidia-settings
# Improve:
# Documentation:
#    Configure `nvidia-settings` as desired. Print metamode value with following command.
#    nvidia-settings -q CurrentMetaMode
#    Use everything after the `::`

test -z "${DESIRED}" && test -n "${1}" && DESIRED="${1}"
desired="$( echo "${DESIRED}" | tr 'A-Z' 'a-z' )"
case "${desired}" in
   "both"|"left+right"|"left,right","double")
      echo "Using both monitors."
      nvidia-settings --assign "CurrentMetaMode=DPY-4: nvidia-auto-select @1920x1080 +1920+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}, DPY-1: nvidia-auto-select @1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}"
      ;;
   "one"|"right"|"single")
      nvidia-settings --assign "CurrentMetaMode=DPY-4: nvidia-auto-select @1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}"
      ;;
   *) echo "Unknown option: ${desired}. Aborted." ;
      exit 1 ;
      ;;
esac

And then I wrote a tray icon so it's easy to get to these.

files/2023/12/listings/switch-monitors-trayicon.sh (Source)

#!/usr/bin/env sh
# File: switch-monitors-trayicon.sh
# Location: /usr/local/bin
# Author: bgstack15
# SPDX-License-Identifier: GPL-3.0
# Startdate: 2023-12-05-3 16:29
# Title: Trayicon for switching monitor config
# Purpose: Provide easy drop-down for pcb-009 for monitor control
# History:
# Usage:
# Reference:
#    Heavily ripped keyboard-leds-trayicons
# Improve:
#    There is no loop, so manually touching the kill file does not stop the process like it should.
# Dependencies:
#    raw: mktrayicon, awk, switch-monitors.sh
#    devuan: mktrayicon, mawk | gawk, x11-xserver-utils

# CONFIG FILES
test -z "${SWITCH_MONITORS_CONF}" && SWITCH_MONITORS_CONF="${HOME}/.config/switch-monitors.conf"

# FUNCTIONS

get_conf() {
   # Ripped from framework.sh
   # call: get_conf "${conffile}"
   local _infile="$1"
   local _tmpfile1="$( mktemp )"
   sed -e 's/^\s*//;s/\s*$//;/^[#$]/d;s/\s*[^\]#.*$//;' "${_infile}" | grep -viE "^$" | while read _line ;
   do
      local _left="$( echo "${_line}" | cut -d'=' -f1 )"
      eval "_thisval=\"\${${_left}}\""
      test -z "${_thisval}" && echo "${_line}" >> "${_tmpfile1}"
   done
   test -f "${_tmpfile1}" && { . "${_tmpfile1}" 1>/dev/null 2>&1 ; }
   /bin/rm -rf "${_tmpfile1}" 1>/dev/null 2>&1
}

clean_switch_monitors_trayicon() {
   { test -e "${switch_monitors_icon}" && echo "q" > "${switch_monitors_icon}" ; } 1>/dev/null 2>&1 &
   sleep 1 && rm -f "${switch_monitors_icon}" "${SMT_KILLFILE}"
}

# LOAD CONFIGS
# order is important! The last one called gets precedence.
# instead of simply dot-sourcing the conf file, pass it to get_conf which only applies new values, so this process's environment is preserved
for thisconf in "${SMT_CONF}" "${SMT_USER_CONF}" "${SMT_GLOBAL_CONF}" ;
do
   test -r "${thisconf}" && get_conf "${thisconf}"
done

# DEFAULTS in case configs did not have these values
test -z "${SMT_ICON}" && SMT_ICON=display
test -z "${SMT_KILLFILE}" && SMT_KILLFILE="/tmp/kill-all-switch-monitors-trayicons"

# INITIALIZATION

switch_monitors_icon="/var/run/user/$( id -u )/${$}.switch_monitors.icon"

mkfifo "${switch_monitors_icon}"
mktrayicon "${switch_monitors_icon}" &
{
   echo "i ${SMT_ICON}"
   echo "t pcb-009 easy display settings"
   echo "m right,switch-monitors.sh right|both,switch-monitors.sh both|-----|quit,echo 'q' > ${switch_monitors_icon} ; touch "${SMT_KILLFILE}""
} > "${switch_monitors_icon}"

rm -f "${SMT_KILLFILE}"

trap 'trap "" 2 ; touch "${SMT_KILLFILE}" '  2 # CTRL-C
wait %1

# safety shutoff
clean_switch_monitors_trayicon

References

Weblinks

NVIDIA - ArchWiki#Using_nvidia-settings

ddccontrol for monitors

bgstack15 — Wed, 12 Oct 2022 12:58:53 GMT

The story

I use an Nvidia graphics card on my Devuan Ceres desktop. I also use two monitors, and a kvm switch for one of the monitors. On the other monitor I have a 3-input HDMI input switcher. Some article I read on the Internet suggested that one can use software to interact with the monitors, using the ddc protocol. I think DDC is how my old computers could recognize what was plugged in to my VGA port (and nowadays, VGA, displayport, and unfortunately some HDMI) by name.

On GNU/Linux, that software is ddccontrol. To enable Nvidia to pass through ddc protocol, I had to enable a module parameter. I set value in new file /etc/modprobe.d/nvidia-registry.conf which turns on the i2c capabilities of my 01:00.0 VGA compatible controller: NVIDIA Corporation GP107 [GeForce GTX 1050 Ti] (rev a1).

options nvidia NVreg_RegistryDwords="RMUseSwI2c=1"

I re-ran update-initramfs to ensure even the initram has this new setting.

sudo update-initramfs -u -k $( uname -r )

After a reboot (just to be sure), in userspace, I can now query the monitor. To learn the input field:

$ ddccontrol dev:/dev/i2c-4 -d | grep -i input
 Control 0x60: +/5/3 C [Input Source Select (Main)]

My two identical Samsung monitors ended up needing slightly different ddccontrol commands. I suspect this is due to one is connected via HDMI and one via DP.

My monitor-left-hdmi.sh command:

ddccontrol dev:/dev/i2c-4 -r 0x60 -w '5'

monitor-left-dp.sh:

ddccontrol dev:/dev/i2c-4 -r 0x60 -w '3'

monitor-right-vga.sh:

ddccontrol dev:/dev/i2c-2 -r 0x60 -w '1'
ddccontrol dev:/dev/i2c-2 -r 0xdb -w '4'
ddccontrol dev:/dev/i2c-2 -r 0xdc -w '6'
ddccontrol dev:/dev/i2c-2 -r 0xeb -w '253'

monitor-right-hdmi.sh:

ddccontrol dev:/dev/i2c-2 -r 0xdb -w '253'
ddccontrol dev:/dev/i2c-2 -r 0xdc -w '260'
ddccontrol dev:/dev/i2c-2 -r 0xeb -w '9'
ddccontrol dev:/dev/i2c-2 -r 0x60 -w '5'

I learned all those by evaluating the output of ddccontrol dev:/dev/i2c-4 -d after manually choosing the inputs I cared about.

These monitors didn't have prebuilt profiles in the ddccontrol-db.

Adjust touchscreen input for fullscreen aspect ratio

bgstack15 — Sat, 06 Nov 2021 12:40:17 GMT

My Thinkpad X230 of course has the 1366x768 display endemic to the era. I wanted to use an old program that is best viewed in a full-screen, 640x480 resolution. Of course xrandr can set this resolution no problem, but the tablet input needs to be adjusted to scale to the size of the display.

Here is my solution for that.

	`#!/bin/sh`
	`# File: set-touchscreen-resolution.sh`
	`# Locations:`
	`# LTB-019:/usr/local/bin/`
	`# /mnt/public/Support/Platforms/Thinkpad-X230/screen/`
	`# Author: bstack15`
	`# Startdate: 2021-10-30 20:42`
	`# Title: Script that Adjusts Thinkpad Touchscreen to Aspect Ratios of Smaller Resolutions`
	`# Purpose: change touchscreen input to match resolution.`
	`# History:`
	`# Usage:`
	`# set-touchscreen-resolution.sh 640 480`
	`# References:`
	`# https://stackoverflow.com/questions/20558710/bc-truncate-floating-point-number/20562313#20562313`
	`# Improve:`
	`# discover how to actually make the logic work with 1366x768`
	`# Dependencies:`
	`# xsetwacom`
	`# Documentation:`
	`# full height input is always useful on the Thinkpad X230, so we are only calculating X.`

	`# get touchscreen native aspect ratio`
	`xi="$( xinput list )"`
	`stylus="$( echo "${xi}" \| awk '/stylus.slave.pointer/{print}' \| awk -F'=' '{print $2}' \| awk '{print $1}' )"`
	`touch="$( echo "${xi}" \| awk '/touch.slave.pointer/{print}' \| awk -F'=' '{print $2}' \| awk '{print $1}' )"`
	`eraser="$( echo "${xi}" \| awk '/eraser.slave.pointer/{print}' \| awk -F'=' '{print $2}' \| awk '{print $1}' )"`

	`#desiredx=640`
	`#desiredy=480`
	`desiredx="${1}"`
	`desiredy="${2}"`
	`# for some reason the real aspect ratio does not work, but setting a 1x1 ratio will make the tablet input work`
	`test "${desiredx}" = "1366" && test "${desiredy}" = "768" && { desiredx=1 ; desiredy=1 ; }`
	`test -z "${desiredx}" && test -z "${desiredy}" && { desiredx=1 ; desiredy=1 ; }`

	`# For each item, because the resolution can be different across items.`
	`for word in ${touch} ${stylus} ${eraser} ;`
	`do`
	`origArea="$( xsetwacom get "${word}" Area )"`
	`xsetwacom set "${word}" ResetArea`
	`resetarea="$( xsetwacom --get "${word}" Area )"`
	`xsetwacom set "${word}" Area ${origArea}`
	`fullx="$( echo "${resetarea}" \| awk '{print $3}' )"`
	`fully="$( echo "${resetarea}" \| awk '{print $4}' )"`
	`width="$( printf "scale=4\na=(${fullx}/(${desiredx}/${desiredy}))\na\n" \| bc )"`
	`x1="$( printf "scale=4\ndefine trunc(x) { auto s; s=scale; scale=0; x=x/1; scale=s; return x }\na=(${fullx}/2)-(${width}/2)\ntrunc(a)\n" \| bc )"`
	`x2="$( printf "scale=4\ndefine trunc(x) { auto s; s=scale; scale=0; x=x/1; scale=s; return x }\na=${x1}+${width}\ntrunc(a)\n" \| bc )"`
	`#echo "For width=${width} run:"`
	`echo "setting device ${word} Area ${x1} 0 ${x2} ${fully}"`
	`test -n "${APPLY}" && {`
	`xsetwacom set "${word}" Area ${x1} 0 ${x2} ${fully}`
	`}`
	`done`

Any guidance on the mathematics for the aspect ratios would be welcome! Notice how I had to hardcode the full resolution of the display (1366x768). Apparently my math is... off.

References

A lot of my own lousy mathematics
Wacom tablet - ArchWiki
linux - bc truncate floating point number - Stack Overflow

Menu for choosing screen orientation on a tablet computer

bgstack15 — Fri, 29 Oct 2021 12:44:23 GMT

Overview

I found some great sources on the Internet for how to set up a menu for choosing screen orientation on a tablet computer that doesn't have gyros or other sensors to orient the screen "up." My solution involves a number of scripts, a .desktop file, and some config entries in a few spots.

Design

I wanted a menu, with arrows, where the user selects the arrow that points up. So the current screen orientation will affect the chosen value. Research on the Internet showed that I will need to rotate the tablet input and optionally the wallpaper. My environment uses fluxbox, so the architecture will hardcode in fluxbox controls but obviously this can be adapted as needed.

Dependencies

yad
xrandr
xinput
fbsetbg (optional)
mktrayicon (optional)

Files involved

I placed all the scripts in /usr/local/bin. The desktop file is placed in /usr/share/applications.

Files modified

/etc/rc.local
~/.fluxbox/keys

New files

rotate-menu.sh
rotate.sh
rotate-wallpaper.sh
rotate-trayicon.sh
rotate-trayicon.desktop

Rotate menu

The main GUI is in rotate-menu.sh. This script uses yad (because it had way fewer dependencies than zenity) to generate a simple window with buttons. The chosen orientation is calculated relative to the current orientation, and the true orientation is passed to the Rotate script.

#!/bin/sh
# File: rotate-menu.sh
# Locations:
#    /usr/local/bin/
# Author: bgstack15
# Startdate: 2021-10-20 09:50
# SPDX-License-Identifier: GPL-3.0
# Title: Menu for Choosing Screen Orientation on Thinkpad X230
# Purpose: Make it easy to rotate screen
# Usage: ./rotate-menu.sh
#    or press the "screen rotate" button
# Dependencies: yad, xrandr
#    In /etc/rc.local: "setkeycodes 6c 132"
#    In ~/.fluxbox/keys "140 :Exec /usr/local/bin/rotate-menu.sh"
# Reference:
#    https://forums.linuxmint.com/viewtopic.php?t=110395
#    https://forum.thinkpads.com/viewtopic.php?t=108785
#    https://wiki.archlinux.org/title/HiDPI#GDK_3_(GTK_3)
# Improve:
# Documentation:
#    Chose yad because zenity wanted 121MB of dependencies and yad needed no additional dependencies.
#    YES, the fluxbox and rc.local keycodes are not the same. I don't know why they need to be different to work.

rotate_script=/usr/local/bin/rotate.sh
order="left,normal,right,inverted,left,normal,right"

current_orientation="$( xrandr -q --verbose | grep 'connected' | grep -o  -E '\) (normal|left|inverted|right) \(' | grep -o -E '(normal|left|inverted|right)' )"
echo "Currently facing: ${current_orientation}"

new_orientation() {
   # call: new_orientation ${orientation} ${NUMBER}
   # where number is [0-3] and we want to move to the orientation adjacent to old orientation
   first="$( echo "${order}" | tr ',' '\n' | awk -v "or=${1}" '$0 ~ or && a==0 {a=1;print NR}' )"
   #echo "first=${first}"
   echo "${order}" | tr ',' '\n' | awk -v "add=${2}" -v "or=${first}" 'NR==(add+or){print;}'
}

GDK_SCALE=2 yad --form --center --buttons-layout=center --window-icon=display --title='Change screen orientation' --align=center --field='Which direction should be up?:LBL' --button='!go-previous:152' --button='!up:150' --button='!down:151' --button='!go-next:153' 1>/dev/null 2>&1
result=$?
#echo "${result}"
case "${result}" in
   150) echo "pressed button up" ; new="$( new_orientation ${current_orientation} 0 )" ;;
   151) echo "pressed button down" ; new="$( new_orientation ${current_orientation} 2 )" ;;
   152) echo "pressed button left" ; new="$( new_orientation ${current_orientation} 3 )" ;;
   153) echo "pressed button right" ; new="$( new_orientation ${current_orientation} 1 )" ;;
   *) echo "invalid response: ${result}" ;;
esac

echo "new rotation should be ${new}"
"${rotate_script}" "${new}"

Rotate

The actual rotation logic is stored in a separate script, rotate.sh. Decoupling the UI from the functions is always useful, particularly for someone who wants to run arbitary rotation commands. This script rotates the X screen, and also the stylus, eraser (other end of the stylus?), and touch inputs. Without the input rotations, hilarity can ensue. You should try it sometime just to see what it's like.

#/bin/sh
# File: rotate.sh
# Locations:
#    /usr/local/bin/
# Author: bgstack15
# Startdate: 2021-10-20
# SPDX-License-Identifier: GPL-3.0
# Title: Rotate display and inputs
# Purpose: Rotates X display and also the inputs
# History:
# Usage:
#    rotate.sh [left|right|normal|inverted]
#    Called from rotate-menu.sh, which calculates which of the directions to use.
# Reference:
#    https://forums.linuxmint.com/viewtopic.php?t=110395
# Improve:
# Dependencies:
#    xinput

test -z "${DISPLAY}" && { echo "Fatal! Need DISPLAY set. Aborted." 1>&2 ; exit 1 ; }
test -z "${ROTATE_WALLPAPER_SCRIPT}" && ROTATE_WALLPAPER_SCRIPT=/usr/local/bin/rotate-wallpaper.sh
orientation="${1}"

case "${orientation}" in
   normal) wacom_orientation="none" ;;
   inverted) wacom_orientation="half" ;;
   left) wacom_orientation="ccw" ;;
   right) wacom_orientation="cw" ;;
   *) echo "Invalid orientation ${orientation}. Aborted." 1>&2 ; exit 1 ;;
esac

# collect stylus, touch, and eraser IDs
xi="$( xinput list )"
stylus="$( echo "${xi}" | awk '/stylus.*slave.*pointer/{print}' | awk -F'=' '{print $2}' | awk '{print $1}' )"
touch="$( echo "${xi}" | awk '/touch.*slave.*pointer/{print}' | awk -F'=' '{print $2}' | awk '{print $1}' )"
eraser="$( echo "${xi}" | awk '/eraser.*slave.*pointer/{print}' | awk -F'=' '{print $2}' | awk '{print $1}' )"

# MAIN
xrandr -o "${orientation}"
"${ROTATE_WALLPAPER_SCRIPT}"
xsetwacom set "${stylus}" rotate "${wacom_orientation}"
xsetwacom set "${touch}" rotate "${wacom_orientation}"
xsetwacom set "${eraser}" rotate "${wacom_orientation}"

Rotate wallpaper

For additional aesthetic value, I decided to build a script that rotates the wallaper. The admin can establish symlinks in directory /etc/installed/wallpapers, named the same as the orientations that X reports (normal, inverted, left, right). The symlinks can point to whatever you want.

$ cd /etc/installed/wallpapers
$ ln -s wallpaper_wide.jpg normal
$ ln -s wallpaper_wide.jpg inverted
$ ln -s wallpaper_tall.jpg left
$ ln -s wallpaper_tall.jpg right

The script rotate-wallpaper.sh uses these symlinks.

#!/bin/sh
# File: rotate-wallpaper.sh
# Locations:
#    /usr/local/bin/
# Author: bgstack15
# Startdate: 2021-10-20 22:23
# SPDX-License-Identifier: GPL-3.0
# Title: Choose Wallpaper for Current Orientation
# Purpose: Choose wallpapers from the symlinks in /etc/installed/wallpapers/
# History:
# Usage:
#    rotate-wallpaper.sh
#    Called by ~/.fluxbox/startup or manually, or from rotate-menu.sh
# Reference:
#    rotate-menu.sh
# Improve:
# Dependencies:
#    xrandr, fbsetbg
#    symlinks named same as xrandr orientations: normal, right, inverted, left
# Documentation:
current_orientation="$( xrandr -q --verbose | grep 'connected' | grep -o  -E '\) (normal|left|inverted|right) \(' | grep -o -E '(normal|left|inverted|right)' )"
echo "Currently facing: ${current_orientation}"

case "${current_orientation}" in
   normal|inverted|left|right) fbsetbg -f /etc/installed/wallpapers/"${current_orientation}" ;;
   *) echo "Unknown orientation ${current_orientation}! Aborted." ; exit 1 ;;
esac

Tray icon

The configurations described below set up the hardware "Screen rotate" button to trigger rotate-menu.sh. My hardware doesn't always register presses of the button, so I wanted to add a software button. This script, rotate-trayicon.sh, uses mktrayicon to make a simple icon that runs the main GUI when clicked.

#!/bin/sh
# File: rotate-trayicon.sh
# Locations:
#    /usr/local/bin/
# Author: bgstack15
# Startdate: 2021-10-21 11:47
# SPDX-License-Identifier: GPL-3.0
# Title: Tray icon for rotate-menu
# Purpose: Display the display icon in the system tray, because the "rotate screen" physical button is not always registered.
# History:
# Usage:
#    rotate-trayicon.sh
#    Can be called from ~/.fluxbox/startup
# References:
# Improve:
# Dependencies:
#    mktrayicon
fifo="${XDG_RUNTIME_DIR:-/tmp}/$$.icon"
mkfifo "${fifo}"
mktrayicon "${fifo}" &
echo "i display" >> "${fifo}"
echo "m Exit,echo 'q'>> ${fifo};sleep 2;rm ${fifo};" >> "${fifo}"
echo "c /usr/local/bin/rotate-menu.sh" >> "${fifo}"
echo "s" >> "${fifo}"

Tray icon menu entry

In case the trayicon needs to be started from the application menu, here is my rotate-trayicon.desktop file.

[Desktop Entry]
Comment=Tray icon for asking user the desired screen orientation
Exec=rotate-trayicon.sh
Categories=Utility;TrayIcon;
GenericName=Display orientation helper tray icon
Icon=display
Keywords=display;rotate;
Name=Rotate-menu tray icon
Terminal=false
Type=Application

Configurations

To take advantage of my specific hardware's rotate-screen button, I had to assign the scancode to a keycode. References [1][1] and [2][2] are great for describing how to assign a keycode to a scancode (what happens when you press a button). If you need a reminder, use xev(1) and showkey(1).

Once you know the scancode for your button, set up the setkeycode command in /etc/rc.local.

setkeycodes 6c 132

And then in ~/.fluxbox/keys I used this directive.

140 :Exec /usr/local/bin/rotate-menu.sh

Yes, for some reason the setkeycode and code that Fluxbox uses are not the same. I don't know why, unless one of them is not base10 or something. But I got it to work, some of the time anyway.

References

Linux find running display manager

bgstack15 — Sun, 31 Dec 2017 13:36:22 GMT

In GNU/Linux, if you ever need to know what your currently running display manager is, here is how you can find it:

x="$( sudo lsof -F '' /tmp/.X11-unix/X0 | head -n1 )" ; x="${x#p}"
display_manager="$( ps -p $( ps -o ppid -p ${x} | tail -n +2 ) -ho command )"
thisdm="$( basename "${display_manager}" )"

References

Weblinks

https://unix.stackexchange.com/questions/20370/is-there-a-simple-linux-command-that-will-tell-me-what-my-display-manager-is

Multiple monitors on Windows guest in KVM

bgstack15 — Sun, 05 Nov 2017 13:46:50 GMT

Introduction

It is easy to set up a virtual machine with the virt-manager GUI. To add a second monitor (or more) is also pretty easy, once you know how to do it. However, to view a second monitor simultaneously with the first, you will need to use the tool remote-viewer. In virt-manager, select "Show virtual hardware details." Add a new video card. A basic QXL type should be sufficient. It is possible to connect to the guest's displays over the network, if you configure it to be possible. For example, you use your desktop Virtual Machine Manager to connect to a server's libvirt via a connection string like qemu+ssh://root@vm1.ipa.example.com/system. On that virtual machine's "Display spice" virtual hardware, modify the address tag to "All interfaces." Also note the the port number given to this guest. In my screenshot you can see mine is port 5907. You will want to open up the firewall on the vm host. I suggest just using the vdsm definition, which is for the oVirt project and includes TCP ports 5900-6923.

sudo firewall-cmd --permanent --add-service=vdsm; sudo firewall-cmd --reload

You will need to shut down (not reboot) the guest if it is running at the time, for it to be able to use the new virtual hardware or pretty much any new setting. Once the virtual machine is running again, use "Remote Viewer" in the GUI, or run from the command line.

remote-viewer spice://vm1.ipa.example.com:5907

Improvements

Learn how to do this in the cli, including maybe at the virt-install statement. Or at least how to retro-fit an existing domain.

References

search "kvm spice guest windows multiple monitors"
Shamelessly ripped off from https://solus-project.com/forums/viewtopic.php?f=11&t=8663
spice guest tools https://www.spice-space.org/download.html

Find running X sessions

bgstack15 — Wed, 06 Sep 2017 13:17:34 GMT

tl;dr

{ ps -eo pid,command | awk '/-session/ {print $1}' | while read thispid; do cat /proc/${thispid}/environ | tr '\0' '\n' | grep "DISPLAY" | sed -e "s/^/${thispid} $( stat -c '%U' /proc/${thispid}/comm ) $( basename $( readlink -f /proc/${thispid}/exe ) ) /;"; done; } 2>/dev/null | grep -iE "xfce|cinnamon"

Explanation

I was working on a shell script that affects the running desktop environments. In order to find the running processes, owners, executable, and display session, I whipped up this one-liner. Obviously here, I limit my searches to specific types of desktop environments. I was getting a dbus-daemon and at- spi2-registryd which I neither understand nor care about, so I added the regular expression search at the end. Feel free to modify for your own use. Example output:

$ { ps -eo pid,command | awk '/-session/ {print $1}' | while read thispid; do cat /proc/${thispid}/environ | tr '\0' '\n' | grep "DISPLAY" | sed -e "s/^/${thispid} $( stat -c '%U' /proc/${thispid}/comm ) $( basename $( readlink -f /proc/${thispid}/exe ) ) /;"; done; } 2>/dev/null | grep -iE "xfce|cinnamon"
1791 bgstack15-local xfce4-session DISPLAY=:0