Linux often used commands

Editing

# diff
vimdiff gives a graphical feel

# Edit files with windows line endings
Pass the -b option to vi, or, once vi is loaded, type :e ++ff=unix.

# change the typing language, e.g. to hindi from English
alt + caps

Shell

# to make the statements/exports in a.sh available in current process
source a.sh

# search recursively for pattern
grep -r --include "*.jsp" pattern

# Sort files by reverse timestamp
find . -name "*.jsp" -printf '%T@ %t %p\n' | sort -k 1 -n -r

# line count
wc -l

FileSystem

# disk usage
df
du

Software management

# to invoke mint's package manager
sudo mintinstall

#to update flash plugin for FF
apt-get install flashplugin-installer

Services

# manage startup of services
initictl list/start/stop/restart <service>

#view/manage services
systemctl


# Remove a service from startup. Here apache
sudo update-rc.d apache2 remove

# Add a service apache2 back into the autostart

sudo update-rc.d apache2 defaults


# Enable autostart
sudo update-rc.d apache2 enable

# Disable autostart. Difference from remove is that the entry is kept.

update-rc.d apache2 disable 

#Can also be done with systemctl, depending on the version
#or the service command :
service apache2 start

Apache start/stop

sudo apachectl start/stop

# apache conf location
/etc/apache2/apache2.conf

Mail

postfix start/stop

d a-z or d * to delete mail messages

Processes

# view ports, in this case for amqp service
nmap -p 1-65535 localhost | grep mq

# view processes
ps -ef
netstat

Pdf

# pdftk remove password from pdf. may throw error, its outdated
pdftk input_pw <pass> in.pdf output out.pdf

# or use qpdf if pdftk gives error
qpdf --password=<your-password> --decrypt /path/to/secured.pdf out.pdf

Images

# image magic join images +for horz, - for vert
convert a.jpg b.jpg -append c.jpg

# image magic pdf to image
convert -density 100 -colorspace rgb test.pdf -scale 200x200 test.jpg

Md5

# check md5 sum of file. Tr to convert case
md5sum spark-2.2.1-bin-hadoop2.7.tgz | tr '[:lower:]' '[:upper:]' | grep C0081F6076070F0A6C6A607C71AC7E95

System Settings

Swap

There is a swappiness setting on ubuntu, which might make use of swap even when main memory is available. A lower value will prevent this
cat /proc/sys/vm/swappiness
sudo sysctl vm.swappiness=10

swapoff -av

swapon -av to reset any already used swap

Remote

# shutdown/restart remote PC over remmima
shutdown /s /t 0
shutdown /r /t 0

teamviewer --daemon stop