mag37

Setting up a keypair and adding it to remote server:

Generate keypair (will be asked where to save if no -f, default is fine):

ssh-keygen -t ed25519 -f ~/.ssh/filename -C "<comment/email>"

Copy public key to remote server:

# with ssh-copy-id tool:

A small script to swap between main monitor+audio source to secondary monitor+audio. Either just swap which is set as primary, or also disable the secondary. Add "Command or Script" shortcut to trigger it from the keyboard.

#!/usr/bin/env bash


# Enable/Activate both monitors and get info from `kscreen-doctor -o | grep -A3 Output` 
# Get audio sinks from `pactl list sinks short`

Rescue a borked Grub in Arch

Boot arch install usb

• list devices with lsblk

mount root drive

• if LUKS:
  • cryptsetup luksOpen /dev/sda2 myEncryptedVolume
  • mount /dev/mapper/myEncryptedVolume /mnt
• if BTRFS:
  • mount -o subvol=@ /dev/sda2 /mnt
• if LUKS+BTRFS:

Docs:

-nocerts      No certificates at all will be output.
-clcerts      Only output client certificates (not CA certificates).
-nokeys       No private keys will be output.
-nodes        Don't encrypt the private keys at all.

Examples:

Print Power_On_Hours from smartctl

for d in sd{a..e}; do smartctl -a /dev/$d | \
  awk -v d="$d" '/Power_On/ {print "PowerOnHours "d, int($10), "("int($10 / 24)" days)"}' ; done

Example output:

PowerOnHours sda 23050 (960 days)

Basic resizing with different results

# Resize to fit within 800x600, preserving aspect ratio
magick input.png -resize 800x600 output.png
# 1000x1000 -> 600x600, 1600x1000 -> 800x500

# Resize by percentage, rounds to closest integer pixel which can be off compared to exact pixels
magick input.png -resize 50% output.png
# 1000x800 -> 500x400, 800x593 -> 400x297 (half a pixel too high, could distort)

Calculate new SUBUID range:

PREVIOUS="$(sort -t: -k2 -n /etc/subuid | tail -n1)" && PREVIOUS="${PREVIOUS#*:}" && echo "$PREVIOUS"
# ex.out: 165536:65536

FIRST="$((${PREVIOUS%:*}+${PREVIOUS#*:}))" && echo "$FIRST"
# ex.out: 231072

NEW=${FIRST}-$((${FIRST}+65535)) && echo "$NEW"
# ex.out: 231072-296607

Convert EPOCH timestamp to datetime within VIM

Select all lines then: (remember the dot within [0-9.] if decimal-epoch)
:'<,'>s/\([0-9.]\+\)/\=strftime('%c', submatch(1))

Result:

# From:
1779764414.0, test, ABC123, X
# To:

convert 10-12bit h265 to 8bit h264

# with specific formats and to mkv
ffmpeg -i input.mkv -map 0 -c:v libx264 -crf 18 -vf format=yuv420p -c:a copy output.mkv

# quick and default and convert to mp4
ffmpeg -i input.mkv -c:v libx264 -c:a aac output.mp4