How to extract subtitles from an MKV video with FFMpeg

ffmpeg -i source.mkv -scodec srt  subsoutput.srt
or
ffmpeg -i source.mkv -scodec ass  subsoutput.ass

How to capture full page screenshot (screen capture) in Firefox

Shift F2 to open the Firefox developer toolbar, then enter the command:

screenshot --fullpage

The screenshots are saved into the downloads directory

How to replace your webmin certificate with a new self-signed certificate

openssl req -x509 -newkey rsa:2048 -keyout /etc/webmin/miniserv.pem -out /etc/webmin/miniserv.pem -days 365 -nodes -subj "/C=GB/ST=England/L=London/O=EU/CN=www.mywebsite.com"

openssl x509 -x509toreq -in /etc/webmin/miniserv.pem -signkey /etc/webmin/miniserv.pem >> /etc/webmin/miniserv.pem

/etc/init.d/webmin restart

How to burn (hardcode) subtitles into an MP4 video from an MKV video with embedded subtitles

ffmpeg -i "My Video.mkv" -vf subtitles="My Video.mkv"  "My Video".mp4