ssh keys usage reminder (simplest home case)

* ssh key setup
** generate
example for github:
ssh-keygen -t ed25519 -C "your_email@example.com"
** client .ssh/config (private key per host)
Host deck
IdentityFile /home/user/.ssh/mydeck
Host github.com
IdentityFile /home/user/.ssh/mygithub
** remote host (server): .ssh/authorized_keys
Copy .pub key contents there.

Minimal script to limit traffic to vpn tunnel using ufw

Having ufw installed, execute the following script with sudo: 

 

ufw --force reset

ufw default deny outgoing
ufw default deny incoming

ufw allow out on tun0 from any to any
# for seeding
ufw allow in on tun0 from any to any


# vpn server ip
#ufw allow out from any to 123.123.123.123
#ufw allow out from any to 123.123.123.0/24
#ufw allow out 1198/udp
#ufw allow in 1198/udp
ufw allow out 1194/udp
ufw allow in 1194/udp

ufw enable
ufw status verbose

Washed out colours on HDMI connection to Dell monitor (wayland, drm, rpi 5, intel)

Intel Xe graphics and Raspberry Pi 5 detect "Dell U2422HE" monitor HDMI and USB-C display port as of accepting a "limited range" of colour values as if it were a TV. The problem of washed out / pale colours and bright (grey) black bars in films was discovered to be fixable when the same monitor was connected to an AMD graphics card when suddenly the colours become vivid with deep blacks. It has turned out that AMD driver detects the monitor correctly and engages full range operation. In KDE one can force "full range" in the display/monitors settings, while for rpi we can override via DRM command. Instal modetest utils:

sudo apt install libdrm-tests

Switch to the console framebuffer mode (CTRL+ALT+F1) and find out which connector is the right one by running

modetest -c

In my case HDMI-1 is connected and has an id of 33, so execute the following command (replace 33 with the connector id):

modetest -M vc4 -w 33:"Broadcast RGB":1

Now the black colour should appear darker when switching back to gui (CTRL+ALT+F7). We need to switch to framebuffer mode because DRM is locked by the wayland compositor, and it will not allow to change the "Broadcase RGB" property from the other process. You can test it via displaying a black image fullscreen, e.g. run gimp, create a new image of your monitor resolution filled with absolute black colour, export to .png, open that png in the image viewer.
See also:
https://forums.raspberrypi.com/viewtopic.php?t=375420
https://superuser.com/questions/1532782/how-to-force-ubuntuwayland-to-output-broadcast-rgb-full-to-a-hdmi-output

Install debian on encrypted volume

See https://www.blakecarpenter.dev/installing-debian-on-existing-encrypted-lvm/ The main points:

- expert install
- "Load installer components from CD. From here, you want to select crypto-dm-modules and rescue-mode."
- ctrl+alt+f2 to jump into a shell
- depmod -a
- cryptsetup luksOpen /dev/sda3 debian-crypt
- vgchange -ay
- ls /dev/mapper
control debian-crypt debian-home debian-root debian-swap
- "Hit ctrl+alt+f1 to return to the Debian installer and continue to Partition disks. Select Manual."
- setup partitions/mount points
- stop before Install the GRUB bootloader to a hard disk. ctrl+alt+f2 to jump into a terminal.
- blkid
- nano /target/etc/crypttab
debian-crypt UUID=98...eaa none luks
- "Continue to the end of the installation. When the generating initramfs step appears, the image will be built using the crypttab file you just modified."  

USB Audio not detected after resume. Edifier M60.

Sometimes USB audio device (e.g. Edifier M60 speakers via usb-c connection) is not detected after resume, or after repluging, although

aplay -l

lists the device, the pipewire server does not add it. Restart pipewire:

systemctl --user restart pipewire

If the former does not help, try the following instead:

systemctl --user restart pipewire pipewire-pulse wireplumber

Fix thinkbook 13s ITL2 headphones noise

echo "0x1d 0x707 0x0" > /sys/class/sound/hwC0D0/init_verbs

8bitdo pro 2 hall joysticks calibration issue

8bitdo pro 2 gamepad with hall effect joysticks has an issue that after pressing the left stick it extends (recalibrates) it's value range beyond the range in the unpressed state, so (in my case) ultimate UP (forward) direction does not register as 100%, so e.g. running mode in games becomes unreachable with the extreme stick position (until you push it). There's an undocumented firmware recalibration mode: https://www.reddit.com/r/8bitdo/comments/1dtkoqx/sticks_are_not_aligned_anyway_to_calibrate_this/

  From 8bitdo support about the Pro 2: 
  
  L1+R1+SELECT Hold 10sec start calibration
  
  Rotate both joysticks 3turns *Simultaneously clockwise
  
  Fully press both triggers 3times Press all combination keys again to complete the calibration
  
  Turn-off the controller then turn on again