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linux [2023/11/09 09:12] – created ninelinux [2025/01/09 06:28] (current) – nine
Line 5: Line 5:
 Clean unused/disabled snap packages Clean unused/disabled snap packages
   snap list --all | while read snapname ver rev trk pub notes; do if [[ $notes = *disabled* ]]; then snap remove "$snapname" --revision="$rev"; fi; done   snap list --all | while read snapname ver rev trk pub notes; do if [[ $notes = *disabled* ]]; then snap remove "$snapname" --revision="$rev"; fi; done
 +
 +
 +===== iptables/netfilter =====
 +
 +Restrict to single host, e.g. for prometheus node exporter
 +  iptables -N prometheus  
 +  iptables -A prometheus --src <server-ip> -j ACCEPT
 +  iptables -A prometheus -j DROP
 +  iptables -I INPUT -m tcp -p tcp --dport 9100 -j prometheus
 +  
 +===== docker =====
 +
 +open shell in a running container
 +
 +  docker exec -ti <container-name> /bin/bash
 +
 +
 +===== email =====
 +
 +==== sender guidelines ====
 +
 +  - https://support.google.com/a/answer/14229414
 +  - https://senders.yahooinc.com/best-practices/
 +  - https://senders.yahooinc.com/faqs/
 +  - https://www.bsi.bund.de/dok/TR-03182 
 +
 +==== pdf ====
 +
 +default:
 +  ps2pdf input.pdf output.pdf
 +
 +ghostscript options -dPDFSETTINGS
 +  ps2pdf -dPDFSETTINGS=/ebook input.pdf output.pdf
 +
 +possible options:
 +  -dPDFSETTINGS=/screen (72 dpi)
 +  -dPDFSETTINGS=/ebook (150 dpi)
 +  -dPDFSETTINGS=/prepress (300 dpi)
 +  -dPDFSETTINGS=/printer (300 dpi)
 +  -dPDFSETTINGS=/default Selects the output which is useful for multiple purposes. Can cause large PDFS.
 +
 +===== Video =====
 +
 +compress video for email sending
 +
 +  ffmpeg -i input.mp4 output_compressed.mp4
 +
 +adjust volume 
 +  ffmpeg -i input.avi -af "volumedetect" -vn -sn -dn -f null /dev/null
 +  
 +gives:
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] n_samples: 1839104
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] mean_volume: -43.4 dB
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] max_volume: -31.5 dB
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] histogram_31db: 64
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] histogram_32db: 455
 +  [Parsed_volumedetect_0 @ 0x55f12ff28780] histogram_33db: 1884
 +
 +
 +increase max volume:
 +  ffmpeg -i input.avi -af "volume=30dB" -c:v copy -c:a libmp3lame -q:a 2 output.mp4
 +  
 +  
 +flip image
 +  ffmpeg -i input.mp4 -vf "transpose=2" output.mp4
 +  
 +transpose options:
 +  0 = 90° counter-clockwise and vertical flip (default)
 +  1 = 90° clockwise
 +  2 = 90° counter-clockwise
 +  3 = 90° clockwise and vertical flip
 +
linux.1699521131.txt.gz · Last modified: 2023/11/09 09:12 by nine