Systemd

vim /etc/systemd/system/service_name.service

[Unit]
Description = making network connection up
After = network.target
[Service]
# ExecStart can point to any executable file
ExecStart = /root/scripts/conup.sh
[Install]
WantedBy = multi-user.target

Create executable script

vim /root/scripts/conup.sh;
chmod +x /root/scripts/conup.sh;

Enable service

# systemctl enable connection.service

Basic operations

# systemctl start connection.service
# systemctl stop connection.service

Shrink OS image

Typical case is the shrinking of a RPi microsd card that was dumped to an image file https://web.archive.org/web/20190906231419/https://softwarebakery.com//shrinking-images-on-linux

Grub

Change grub boot order

sudo vim /etc/default/grub

Change GRUB_DEFAULT to one of [number of entry (zero-based), 'Title'subindex] Examples:

'Advanced options for Ubuntu>'3
2

Then, update the grub menu

sudo update-grub

Check the file /boot/grub/grub.cfg for reference

Reinstall grub

  • boot from livecd
  • mount partition where grub was contained (usually OS's partition)
  • sudo tune2fs -L "partition_name" /dev/sdXX ( e.g.: /dev/sda6/ )
  • sudo os-prober
  • sudo grub-install --root-directory=/media/partition_name/ /dev/sda
  • reboot

Create passwordless user programmatically

# useradd -m -c "Samwise the Brave" sam  -s /bin/bash

Creates user with home /home/sam and shell /bin/bash

Find

# Search all files with .old extension and delete them:
find / -name "*.old" -exec /bin/rm {} \;
# Search all files with size > of 100 MB and delete them:
find / -size +100M -exec /bin/rm {} \;
# Recursively change the permissions of all directories
find . -type d -exec chmod 755 {} \;

Top

  • W writes config changes to .toprc
  • E cycles through memory units in the total memory info

Configure stuff

Change locale

With /usr/bin/tzselect you can check what is the timezone your computer should be using

sudo dpkg-reconfigure tzdata If it doesn't work, try the following:

With that timezone, paste the timezone to ~/.profile or ~/.bash_profile, depending on your use case. One of those files (it'll probably work with any sourced file at login) should have one line such as:

TZ='Europe/London'; export TZ

or just execute

Insert unicode characters

Hold down the shift and control keys while typing the letter u and the hex values of the Unicode character you wish to enter. Example: Hold control and shift and type U1F60F ‍😏

Add dictionaries to /usr/share/dict/

$ sudo apt-cache search --names-only swedish
$ sudo apt-get install wswedish

Mouse - Third button

sudo vim /usr/share/X11/xorg.conf.d/middle-mouse-button.conf

And paste this

Section "InputClass"
    Identifier "middle button emulation class"
    MatchIsPointer "on"
    Option "Emulate3Buttons" "on"
EndSection

or check this wiki ubuntu

Webcam

List video devices

  • v4l2-ctl --list-formats-ext
  • v4l2-ctl --list-devices

Find resolution of webcam

  • lsusb list usb devices, get params of webcam
  • lsusb -s 003:074 -v | egrep "Width|Height"

down vote accepted I had the same problem and managed to fix it by setting the defaults for both gvfs as well as xdg.

check defaults with:

This probably will only work with gnome, kde and xfce

#Check currently available apps
xdg-mime query default x-scheme-handler/magnet
gvfs-mime --query x-scheme-handler/magnet

# Set new app, providing it's in /usr/share/applications/
xdg-mime default qBittorrent.desktop x-scheme-handler/magnet
gvfs-mime --set x-scheme-handler/magnet qBittorrent.desktop

Notifications

notify-send -u critical "The potato finished cooking"

Get OS version

uname -a

and

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.2 LTS
Release:        16.04
Codename:       xenial

Motion

Make folders accessible

sudo mkdir -p /var/run/motion; sudo chown -R $USER:$USER /var/run/motion;
sudo mkdir -p /etc/motion/; sudo chown -R $USER:$USER /etc/motion/;
sudo mkdir -p /var/log/motion/; sudo chown -R $USER:$USER /var/log/motion/;

Configuration file

/etc/motion/motion.conf

Generate random chars

tr -c -d '0123456789abcdefghijklmnopqrstuvwxyz'  < /dev/urandom | dd bs=32 count=1 2>/dev/null; echo

Monitor screen locking

exit_report(){
echo "$(date) Monitoring Terminated."
}
trap "exit_report; exit;" 0
lockmon() {
adddate() {
    while IFS= read ­r line; do
      echo "$(date) $line" | grep "boolean" | sed 's/   boolean true/Screen Locked/'
| sed 's/   boolean false/Screen Unlocked/'
    done
}
echo "$(date) Monitoring Started."
dbus­monitor ­­session "type='signal',interface='org.gnome.ScreenSaver'" | adddate
}
lockmon >> lock_screen.log

How to fix ‘$MFTMirr does not match $MFT (record 0)’

  • install ntfsprogs
  • sudo ntfsfix /dev/partitionName