Linux Scripts

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Introduction

Over the years, I have build up several useful scripts to use on Linux systems. I'll try to document them here!

FFMPEG Tricks

Compress all FLAC in subfolders to OPUS

Compress all FLAC audio files in subfolders to OPUS at 128 Kbit/s (near-transparent), while maintaining the metadata tags and album art.

find ./ -name '*.flac' -exec bash -c 'ffmpeg -i "$0" -f flac - | opusenc - --bitrate 128 --vbr --comp 10  "${0/flac/opus}" && rm -v "$0"' {} \;

We use find to select all the flac files, and run the bash files. The first runs ffmpeg and pipes the output to opusenc. The reason is if you use ffmpeg to save to opus files, the album art is lost, whereas when piped in to opusenc, it is encoded properly.

Visualize music into notes

Sometimes I get curious and want to break down a song to it's core melodies, FFMPEG has a cqt filter (like fft), that can convert an audio file into a visual based on the notes. I also realized you can do this in real-time with decent latency using ALSA.

ffmpeg -f alsa -ac 2 -i pulse -filter_complex "[0:a]showcqt=s=1280x720:fps=30:[out]" -map "[out]" -f sdl -
  • This will try capturing a microphone by default, use 'pavucontrol' to change the captured input to loopback for your speaker.
  • I tried to use '-f pulseaudio' instead, but it just ends up being very stuttery and with much higher latency, whereas the alsa version is so much smoother and lower latency.
  • You can change the resolution and fps are needed, I sometimes daisy-chain multiple effects.
  • Output as SDL has much lower latency from my testing. I used to pipe it into mpv with no buffer, but this is even faster


Older revision of this command I used to use as reference:

ffmpeg -f pulse -ac 2 -i default -filter_complex "[0:a]showcqt=s=1280x720:fps=30:[out]" -map "[out]" -r 30 -c:v rawvideo -f matroska - | mpv --no-cache --untimed --no-demuxer-thread -

This stutters a bit more, but might be preferred in some cases. It also uses pulseaudio directly. I switched to using rawvideo instead of other codecs, since rawvideo has a much lower latency, as there is no need for compression and decompression, which doesn't matter since we're piping it for playback anyway.

Misc Stuffs

Mirror all files from a website

Mirror all the files off of a website, with the full folder structure

wget -m -p -E -k -K -np https://example.com/


Mount Seagate external drive without UAS

Normally, you can't run smartctl on a Seagate external drive since they use UAS (USB attached SCSI), which might make it a bit faster for planar drives, but smartctl doesn't support reading SMART data over UAS.

First, unmount and unplug the drive if it is in use

Then, remove the usb-storage and uas modules

sudo modprobe -r usb-storage
sudo modprobe -r uas

(or alternatively, use rmmod)

sudo rmmod usb-storage
sudo rmmod uas

Next, before you plug the drive in (which will auto-load uas), you need to load the usb-storage module with the quirk to disable uas for your Seagate drive.

To do this, get the vendor and product id by doing lsusb (the xxxx:yyyy stuff)

Finally, reload the module with the quirk as follows

sudo modprobe usb-storage quirks=0bc2:331a:u

Where the xxxx:yyyy is the vendor and product id for your drive, and the :u tells it to not use uas.


Cannot unmount USB drive

If you try unmounting a disk as follows (wherever you mounted it)

sudo umount /run/media/username/FlashDrive

and you get an error umount: target is busy, it can be very annoying to find the process that is using something from the drive.

You can use `lsof` to check which processes are accessing the files.

lsof | grep '/run/media/username/FlashDrive'

This will show you which process is using which file, which can be useful.


Useful Programs

Some programs that I use often coming soon.