Linux/Snippets

Hardware

• Motherboard

dmidecode -t 2

File system & drives

List directory sizes

clear;   for each in $(ls) ; do du -hs "$each" ; done

Measure execution time

START=$(date +%s.%N)
command
END=$(date +%s.%N)
DIFF=$(echo "$END - $START" | bc)

find file with content

grep -iR "$PATTERN" *

find top 10 biggest files

du -hsx * | sort -rh | head -10

clear file content

echo "" > filename
or
for i in *; do cat /dev/null > $i; done

show hdd power states

sudo hdparm -C /dev/sd?

show SMART data

sudo smartctl -a /dev/sd?

check for bad sectors

fsck.ext4 -cDfty -C 0 /dev/sdxx

Manual SSD Trim

sudo fstrim -v /   

Cron SSD Trim

/etc/scripts/fstrim.sh:

#!/bin/sh
#
echo `date +"%d %b %H:%M:%S"` | tr -d '\n' >> /var/log/fstrim
/sbin/fstrim -v / >> /var/log/fstrim

/etc/cron.d/fstrim:

#
0 * * * * root /etc/scripts/fstrim.sh

delete folder by folder until enough free space (1G)

cd /srv/motion
while [ `df | grep /dev/root | awk '{print $4}'` -lt 1000000 ]; do
ls -r | tail -1 | xargs rm -r
sleep 5
done

Shutdown if HDD idle

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

kernel

remove old kernels

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