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apt-get install haveged
nano /etc/default/haveged # Setup DAEMON_ARGS="-w 1024"
update-rc.d haveged defaults
cat /dev/random | rngtest -c 1000 # Testing Availability of Entropy & Quality of Random Data
cat /proc/sys/kernel/random/entropy_avail # To test the amount of available entropy

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# Create background noise profile from mp3
/usr/bin/sox noise.mp3 -n noiseprof noise.prof

# Remove noise from mp3 using profile
/usr/bin/sox input.mp3 output.mp3 noisered noise.prof 0.21

# Remove silence from mp3
/usr/bin/sox input.mp3 output.mp3 silence -l 1 0.3 5% -1 2.0 5%

# Remove noise and silence in a single command

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# REMEMBER TO USE VISUDO - you can potentially lock yourself out if sudoers file has parse error

# change visudo editor to VIM
Defaults        editor=/usr/bin/vim

# example of /etc/sudoers.d/lbbackup

Cmnd_Alias LS_HARDWARE = /usr/bin/lshw
Cmnd_Alias MOUNT_UDF = /bin/mount -oloop\,rw *
Cmnd_Alias UNMOUNT_UDF = /bin/umount /data/TEMP_UDF_DIR/MOUNT_UDF

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Tar Usage / Cheat Sheet

Compress a file or directory

e.g: tar -czvf name-of-archive.tar.gz /path/to/directory-or-file

• -c: Create an archive.
• -z: Compress the archive with gzip.
• -v: makes tar talk a lot. Verbose output shows you all the files being archived and much.
• -f: Allows you to specify the filename of the archive.

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Setup a Local Only SMTP Email Server (Linux, Unix, Mac)

1 - Point localhost.com to your machine

Most of programs will not accept an email using just @localhost as domain. So, edit /etc/hosts file to make the domain localhost.com point to your machine, including this content to the file:

127.0.0.1 localhost.com

2 - Install Postfix