notes

common CLI commands that I use

Gimp distorting layer colors

Image -> Mode -> RGB

Fixing grub dual boot when windows messes it up

1: Mount root paartition to /mnt, e.g mount /dev/sda3 /mnt

2: Chroot into it: arch-chroot /mnt

3: Mount EFI partition: mount /dev/sda1 /boot/efi

4: Reinstall grub grub-install

5: grub-mkconfig -o /boot/grub/grub.cfg

Fixing after dd or win32diskimager messes with your flash drive:

wipefs --all /dev/sdXX

merge all mp4 files in a folder with ffmpeg without re-encoding

windows:

Create a list of files using CMD

(for %i in (*.mp4) do @echo file '%i') > LIST.txt

linux:

for f in ./*.mp4; do echo "file '$f'" >> LIST.txt; done

finally:

ffmpeg -f concat -safe 0 -i LIST.txt -c copy zout.mp4

merging new audio over an existing mp4 file(audacity noise reduction patch in)

ffmpeg -i IN.mp4 -i IN.ogg -c copy -map 0:v:0 -map 1:a:0 OUT.mp4

cutting out the first pre-padded 10 seconds for noise reduction:

ffmpeg -ss 00:0:10 -i IN.mp4 -c copy OUT.mp4

cutting a video passing in duration params:

(cut from 00:00 to 02:39)

ffmpeg -ss 00:00:00 -i in.mp4 -to 00:02:39 -c copy -copyts out.mp4

compressing an mp4 file with ffmpeg

(just shove it in and the defaults mostly work(TM)), second option for further compression ala martins

ffmpeg -i input.mp4 output.mp4

ffmpeg -i IN.mp4 -c:v libx264 -profile:v high -preset:v slow -crf:v 24 -c:a aac -b:a 128k -movflags +faststart OUT.mp4

another way to overlay the thumbnail to the start of the video(!WARNING! it overwrites the first second with the overlayed image)

It also re-encodes but this is the last step my video production process and in the final step, I always run it through ffmpeg to get a nice compressed version anyways

ffmpeg -i zcleanaudio_merged.mp4 -i 1920.png \
-filter_complex "[0:v][1:v] overlay=0:0:enable='between(t,0,1)'" \
-pix_fmt yuv420p -c:a copy \
FINAL.mp4

creating a video file from an image file using ffmpeg

https://stackoverflow.com/questions/24102336/how-can-i-place-a-still-image-before-the-first-frame-of-a-video

//-t controls the seconds
ffmpeg -loop 1 -framerate 30 -i image.png -c:v libx264 -t 1 -pix_fmt yuv420p image.mp4

to splice in a still image.mp4 file into the front of the video:

//convert the image.mp4 to an image.ts file
ffmpeg -i image.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts image.ts

//and the said video also
ffmpeg -i video.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts video.ts

//finally stick it infront of the video
ffmpeg -i "concat:image.ts|video.ts" -c copy -bsf:a aac_adtstoasc output.mp4

image editing with imagemagick

mirror in the vertical axis:

warning! edits the file in place and overwrites

mogrify -flip *.jpg

mirror in the horizontal axis:

mogrify -flop *.jpg

batch extending an images canvas size(note: use convert if you don't want to overwrite the file):

mogrify -background transparent -gravity south -extent <WIDTH>x<HEIGHT> *.png

compressing png files:

// WARNING! FLAT OUT REPLACES THE PNG FILES
pngquant --force --skip-if-larger --ext .png *.png

blue yeti microphone output fix

Blue yeti microphones have support for sound output but I generarlly don't want to use it. Also install pavucontrol as a nice gui for seeing available sound ouput for applications

// find the analog stereo you want to output to
pactl list sinks short

// set it as the default where n is the number
pactl set-default-sink {n}

fixing windows antimalware taking all the cpu

https://discord.com/channels/239737791225790464/239737791225790464/964668873309814784

According to lhecker https://github.com/lhecker who works at microsoft:

unfortunately that's not your issue... there's a bug were the Antimalware service gets stuck in a loop trying to compact the following DB if it's corrupted: %ProgramData%\Microsoft\Windows Defender\Scans\mpenginedb.db*

deleting those files is safe (actually deleting that entire "Windows Defender" directory should be safe - make backups tho) but given how it says "0MB/s" I think it's unlikely to be the culprit... in either case: if your laptop is part of a corporate network (for instance from a school) it could be your IT department being inexperienced there are certain settings you can make that cause extremely expensive and intrusive AV scanning (and they're better left disabled)

Run files over a cli program with racket:

#lang racket

(define curr-dir (current-directory))
(define files
  (filter
   (lambda (path)
     (define ext (path-get-extension path))
     ;(println ext)
     (cond
       [(boolean? ext) #f]
       [else
        (bytes=? ext #".json")]))
   (directory-list curr-dir)))

(println files)

(define (filename-no-ext p)
  (define ext (path-get-extension p))
  (define str (cond [(string? p) p]
                    [else
                     (path->string p)]))
  (cond
    [(boolean? ext) (path->string p)]
    [else
     (substring str 0 (- (string-length str) (bytes-length ext)))]))
#;
(for
    ([p files])
  (define file (path->string p))
  (define full-path (build-path curr-dir p))
  ; call the cli program you want to run it through
  ; use whereis on linux to find it
  (println p)
  (system* "/usr/bin/pdftoppm" "-png" (path->string full-path) (filename-no-ext file)))

configure static ip on arch during installation:

https://bbs.archlinux.org/viewtopic.php?id=265008

1 - manually stopped systemd-networkd.service and systemd-resolved.service services

systemctl stop systemd-networkd.service systemd-resolved.service

2 - removed any auto-associated ip addr / ip routes.

ip address del 192.168.0.55/24 dev enp0s2
ip route del 192.168.0.0/24 via 192.168.43.223 dev enp0s2

3 - configured static IP address with dhcpcd:

dhcpcd -S ip_address=192.168.1.23/24 -S routers=192.168.1.1 -S domain_name_servers=192.168.1.1 -s 192.168.1.23/24 enp0s2

fix archlinux keyring issues

when simply updating the keyring doesn't work

killall gpg-agent
rm -rf /etc/pacman.d/gnupg
pacman-key --init
pacman-key --populate archlinux
pacman -S archlinux-keyring

linux equiv software to windows:

Windows	Linux
WinDirStat	Qdirtat
Everything	Fsearch

monitor a process and restart it if it crashes

Systemd unit files is the modern way to go:

#  /etc/systemd/system/myprogram.service
[Unit]
Description=My Program Service
After=network.target
StartLimitIntervalSec=20
StartLimitBurst=2

[Service]
WorkingDirectory=/path/to/working/dir
ExecStart=/path/to/your/program
Type=simple
User=youruser
Restart=on-failure
RestartSec=5s


[Install]
WantedBy=multi-user.target

ExecStart: The command to start your program.

Restart=on-failure: Restarts the service if it crashes or exits abnormally.

RestartSec=5s: Waits 5 seconds before restarting.

User=: Optionally specify which user runs the service.

WantedBy=multi-user.target: Ensures it starts at boot.

After=network.target: Ensures network is up before starting (optional depending on needs).

sudo systemctl daemon-reexec      # Reload systemd configuration
sudo systemctl enable myprogram.service # enable it to run at startup
sudo systemctl start myprogram.service # run it now
systemctl status myprogram.service
journalctl -u myprogram.service

How do I write a bash script to restart a process if it dies?

prefer systemd unit files if possible https://stackoverflow.com/questions/696839/how-do-i-write-a-bash-script-to-restart-a-process-if-it-dies

until myserver; do
    echo "Server 'myserver' crashed with exit code $?.  Respawning.." >&2
    sleep 1
done