Saturday, May 15, 2021

Unmounting stuck nfs mounts

 

This usually happens when the nfs server is down, you cannot umount the nfs mount, because the system will say "not found or server not reachable"

$ sudo umount /opt/logs/production

umount.nfs: nfs.local:/var/lib/backup: not found / mounted or server not reachable

umount.nfs: nfs.local:/var/lib/backup: not found / mounted or server not reachable

To fix this, you need to force mount it with lazy flag:

$ sudo umount -f -l /opt/logs/production
where -f is to do force unmount, and -l is for lazy unmounting. From man:
"Lazy  unmount.  Detach  the  filesystem from the filesystem hierarchy now, and cleanup all references to the filesystem as soon as it is not busy anymore."

Post borrowed from: https://www.linuxwave.info/2013/06/unmounting-stuck-nfs-mounts.html

Thursday, May 6, 2021

Fuzzy finder

 I learned recently about the fzf linux cli command. This is a text finder similar to grep but a lot more powerful. It can be used not only to find text but files as well in an interaftive mode.


It exists as a package for debian and its github page is: https://github.com/junegunn/fzf

Saturday, April 24, 2021

Handy ffmpeg Cheatsheet

 https://gist.github.com/steven2358/ba153c642fe2bb1e47485962df07c730

First convert the subtitles to .ass format:
````
ffmpeg -i sub.srt sub.ass
````
Then add them using a video filter:

````
ffmpeg -i in.mp4 -vf ass=sub.ass out.mp4
````

## Extract the frames from a video

To extract all frames from between 1 and 5 seconds, and also between 11 and 15 seconds:

````
ffmpeg -i in.mp4 -vf select='between(t,1,5)+between(t,11,15)' -vsync 0 out%d.png
````

To extract one frame per second only:

````
ffmpeg -i in.mp4 -fps=1 -vsync 0 out%d.png
````

## Rotate a video

Rotate 90 clockwise:

````
ffmpeg -i in.mov -vf "transpose=1" out.mov
````

For the transpose parameter you can pass:

````
0 = 90CounterCLockwise and Vertical Flip (default)
1 = 90Clockwise
2 = 90CounterClockwise
3 = 90Clockwise and Vertical Flip
````

Use `-vf "transpose=2,transpose=2"` for 180 degrees.

## Download "Transport Stream" video streams

1. Locate the playlist file, e.g. using Chrome > F12 > Network > Filter: m3u8
2. Download and concatenate the video fragments:

````
ffmpeg -i "path_to_playlist.m3u8" -c copy -bsf:a aac_adtstoasc out.mp4
````

If you get a "Protocol 'https not on whitelist 'file,crypto'!" error, add the `protocol_whitelist` option:

````
ffmpeg -protocol_whitelist "file,http,https,tcp,tls" -i "path_to_playlist.m3u8" -c copy -bsf:a aac_adtstoasc out.mp4
````

## Mute some of the audio

To replace the first 90 seconds of audio with silence:

````
ffmpeg -i in.mp4 -vcodec copy -af "volume=enable='lte(t,90)':volume=0" out.mp4
````

To replace all audio between 1'20" and 1'30" with silence:

````
ffmpeg -i in.mp4 -vcodec copy -af "volume=enable='between(t,80,90)':volume=0" out.mp4
````

## Deinterlace

Deinterlacing using "yet another deinterlacing filter".

````
ffmpeg -i in.mp4 -vf yadif out.mp4
````

## Create a video slideshow from images

Parameters: `-r` marks the image framerate (inverse time of each image); `-vf fps=25` marks the true framerate of the output.

````
ffmpeg -r 1/5 -i img%03d.png -c:v libx264 -vf fps=25 -pix_fmt yuv420p out.mp4
````

## Extract images from a video

- Extract all frames: `ffmpeg -i input.mp4 thumb%04d.jpg -hide_banner`
- Extract a frame each second: `ffmpeg -i input.mp4 -vf fps=1 thumb%04d.jpg -hide_banner`
- Extract only one frame: `ffmpeg -i input.mp4 -ss 00:00:10.000 -vframes 1 thumb.jpg`

## Metadata: Change the title

````
ffmpeg -i in.mp4 -map_metadata -1 -metadata title="My Title" -c:v copy -c:a copy out.mp4

Sunday, April 18, 2021

Stripping audio from video

 Handy ffmpeg command to strip audio from video with high quality:

ffmpeg -i ../video/$i -q:a 0 -map a $i.mp3

Tuesday, December 22, 2020

Stripping spaces from filenames

 Here is a handy script for stripping spaces from filenames in a directory and all of its subdirectories:


#!/bin/bash


function strip_spaces_from_files {

  for i in *

  do

    newfilename=$(echo $i | tr -s ' ' | tr ' ' '_')

    if [ -e "$newfilename" ]

    then

      echo "$newfilename does not contain any spaces"

    else

      echo "stripping spaces from $newfilename"

      mv "$i" "$newfilename"

    fi

  done

}


INITIALDIR=$PWD

echo "Stripping spaces from current directory $INITIALDIR"

strip_spaces_from_files


echo "Stripping spaces from sub directories"


for subd in $(find ./ -type d)

do

  strippingdot=$(echo "${subd}"|sed 's/^..//')

  echo "switching to directory $INITIALDIR/$strippingdot"

  cd $INITIALDIR/$strippingdot

  echo "stripping spaces"

  strip_spaces_from_files

  echo "going back to initial directory $INITIALDIR"

  cd $INITIALDIR/

done

Friday, December 11, 2020

Validating yaml with python

 python -c 'import yaml, sys; yaml.safe_load(sys.stdin)' < url-monitor-extension-config.yml