View source for Linux/Snippets

== Hardware ==
* Motherboard 
<blockquote>
<pre>
dmidecode -t 2
</pre>
</blockquote>
* HDD
<blockquote>
<pre>
fdisk -l
lsblk
smartctl -a /dev/sda
lshw -c disk
</pre>
</blockquote>

== Packages == 
List packages by size
<blockquote>
<pre>
dpkg-query --show --showformat='${Package;-50}\t${Installed-Size} ${Status}\n' | sort -k 2 -n | grep -v deinstall
</pre>
</blockquote>

Sum of all installed packages
<blockquote>
<pre>
dpkg-query --show --showformat='${Package;-50}\t${Installed-Size} ${Status}\n' | sort -k 2 -n | grep -v deinstall | awk '{s+=$2} END {printf "%.0f\n", s}'
</pre>
</blockquote>

remove old kernels
<blockquote>
<pre>
dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | xargs sudo apt-get --dry-run remove
</pre>
</blockquote>

purge all removed packages
<blockquote>
<pre>
dpkg --list | grep "^rc" | cut -d " " -f 3 | xargs sudo dpkg --purge
</pre>
</blockquote>

== Processes ==
Measure execution time
<blockquote>
<pre>
START=$(date +%s.%N)
command
END=$(date +%s.%N)
DIFF=$(echo "$END - $START" | bc)
</pre>
</blockquote>


== Files / Directories ==
Current script dir
<blockquote>
<pre>
currentpath=$(dirname "$0")
cd $currentpath
</pre>
</blockquote>


List directory sizes
<blockquote>
<pre>
clear;   for each in $(ls) ; do du -hs "$each" ; done

clear;   for each in $(ls) ; do du -hs "$each" ; done | sort -hr
</pre>
</blockquote>

find file with content
<blockquote>
<pre>
grep -iR "$PATTERN" *
</pre>
</blockquote>

find top 10 biggest files
<blockquote>
<pre>
du -hsx * | sort -rh | head -10
</pre>
</blockquote>

find files bigger than 100MB
<blockquote>
<syntaxhighlight lang="bash">
find . -type f -size +100M
</syntaxhighlight>
</blockquote>

clear file content
<blockquote>
<pre>
echo "" > filename
or
for i in *; do cat /dev/null > $i; done
</pre>
</blockquote>

rename directories with spaces to underlines
<blockquote>
<pre>
find -name "* *" -type d | rename 's/ /_/g'
</pre>
</blockquote>

== HDD & SSD ==
show hdd power states
<blockquote>
<pre>
sudo hdparm -C /dev/sd?
</pre>
</blockquote>

show SMART data
<blockquote>
<pre>
sudo smartctl -a /dev/sd?
</pre>
</blockquote>

check for bad sectors
<blockquote>
<pre>
fsck.ext4 -cDfty -C 0 /dev/sdxx
</pre>
</blockquote>

Manual SSD Trim
<blockquote>
<pre>
sudo fstrim -v /   
</pre>
</blockquote>


Cron SSD Trim
:: /etc/scripts/fstrim.sh:
<blockquote>
<pre>
#!/bin/sh
#
echo `date +"%d %b %H:%M:%S"` | tr -d '\n' >> /var/log/fstrim
/sbin/fstrim -v / >> /var/log/fstrim
</pre>
</blockquote>

:: /etc/cron.d/fstrim:
<blockquote>
<pre>
#
0 * * * * root /etc/scripts/fstrim.sh
</pre>
</blockquote>

delete folder by folder until enough free space (1G)
<blockquote>
<pre>
cd /srv/motion
while [ `df | grep /dev/root | awk '{print $4}'` -lt 1000000 ]; do
ls -r | tail -1 | xargs rm -r
sleep 5
done
</pre>
</blockquote>

Shutdown if HDD idle
<blockquote>
<pre>
UPTIME=$(cat /proc/uptime | cut -d ' ' -f 1 | cut -d '.' -f 1)

if [ "$UPTIME" -lt "600" ]
  then exit
fi

lastSDB=$(cat /proc/diskstats | grep "sdb " | tr -s ' ' | cut -d ' ' -f 14 )
lastSDC=$(cat /proc/diskstats | grep "sdc " | tr -s ' ' | cut -d ' ' -f 14 )
lastSDD=$(cat /proc/diskstats | grep "sdd " | tr -s ' ' | cut -d ' ' -f 14 )

sleep 120

newSDB=$(cat /proc/diskstats | grep "sdb " | tr -s ' ' | cut -d ' ' -f 14 )
newSDC=$(cat /proc/diskstats | grep "sdc " | tr -s ' ' | cut -d ' ' -f 14 )
newSDD=$(cat /proc/diskstats | grep "sdd " | tr -s ' ' | cut -d ' ' -f 14 )

if [ "$lastSDB" = "$newSDB" ] && [ "$lastSDC" = "$newSDC" ] && [ "$lastSDD" = "$newSDD" ]
   then /sbin/shutdown -h now
   else echo "changes!!"
fi
</pre>
</blockquote>

Format ext4 with disabled lazy init
<blockquote>
<pre>
mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/sda1
</pre>
</blockquote>

== Multimedia ==
* yt-dlp
** https://github.com/yt-dlp/yt-dlp
<blockquote>
<pre>
yt-dlp --no-keep-video --extract-audio --audio-format mp3 --audio-quality 0 https://www.youtube.com/watch?
</pre>
</blockquote>


[[Category:Linux/Bash]]
[[Category:Linux]]