Ubuntu
===
[toc]
## Commands
### 1.1 Sudo last command
`sudo !!`

### 1.2 No need to write Sudo everytime | Root
`sudo -s `

## Create icon

cd /usr/share/applications
sudo gedit APP_NAME.desktop

Write the below lines

[Desktop Entry]
Name=UnityHub
Comment=UnityHub 3D Game
Exec=/home/jitesh/3d/Unity/UnityHub.AppImage
Icon=/home/jitesh/Pictures/Unity.png
Terminal=false
Type=Application
Categories=Graphics;

:::spoiler or create icon for a command

[Desktop Entry]
Version=1.0
Type=Application
Terminal=true
TerminalOptions=bash
Exec=bash -c "source /opt/ros/indigo/setup.bash;source ~/YOUR/CATKIN/WORKSPACE/devel/setup.bash;/path/to/script.sh"
Icon=/if/you/want/one/icon.png
Name=rosapp

:::

## Extact data from AppImage ([Ref](https://askubuntu.com/questions/1115321/extract-icon-from-appimage))
**First**, look if your AppImage file is using the newest version of its internal format:

/path/to/your.AppImage --appimage-help

If you see the following line in the output:

--appimage-extract Extract content from embedded filesystem image

you can conclude yourself how to proceed. In this case you have a (newer) *type 2* AppImage format in front of you. (The 'path' part of the command may be relative or absolute.)

**Second**, if the first command didn't work, you can use a helper tool. However, you need sudo/root privileges for this: *[download `appimagetool`](https://github.com/AppImage/AppImageKit/releases)* (which off course is available as an AppImage). Make it executable and run:

/path/to/appimagetool-x86_64.AppImage --list /path/to/your.AppImage

This should give you a list of all files and their (relative) paths embedded in *your.AppImage*. To extract *your.AppImage* into a directory named and located at */path/to/somedir* , run

mkdir /path/to/somedir
/path/to/appimagetool-x86_64.AppImage /path/to/your.AppImage /path/to/somedir

**Third**, you can mount AppImages (type 1 as well as type 2) without the helper tool too:

* **Type 1:**

    mkdir mountpoint
    sudo mount -o loop my.AppImage mountpoint/

    # You can now inspect the contents
    # You can now also copy the contents to a writable location of your hard disk

    sudo umount mountpoint/
    # Do not forget the umount step!
    # If you do forget it, your system may exhibit unwanted behavior.

* **Type 2:**

    mkdir mountpoint
    my.AppImage --appimage-offset
    123456   # This is just an example output

    sudo mount my.AppImage mountpoint/ -o offset=123456

    # you can now inspect the contents

    sudo umount mountpoint/
    # Do not forget the umount step!
    # If you do forget it, your system may exhibit unwanted behavior.

***Hint for the 'paranoid':*** If you do not want to trust the AppImage, the third method is preferable. Because running (for type 2 AppImages) `the.AppImage --appimage-extract` or `the.AppImage --appimage-mount` or `the.AppImage --appimage-offset` means you are actually executing an AppImage (though not its content).

## Fix errors with apt update
#### Method 1
`sudo rm -rf /var/lib/apt/lists/*`
##### Update:

To answer the question of @jayarjo in the comment below (*how to re-package the AppImage after modifications?*):

1. You can use *appimagetool* not just to extract an existing AppImage into an AppDir. You can use it to also re-package the AppDir (possibly after some changes) back into a (modified) AppImage.

1. Just run

appimagetool -v /path/to/AppDir

Watch output of command (made verbose by *`-v`*) for the location and name of the newly created AppImage. That's it.
#### Method 2
Update the apt list

code /etc/apt/sources.list

Or check and update here

ls /etc/apt/sources.list.d

## Fix resolution
#### Method 1
open the file

sudo nano /etc/default/grub

find the line

#GRUB_GFXMODE=640x480
edit 640x480 to your resolution eg: 1920x1080, remove the #

for example:

> GRUB_GFXMODE=1920x1080

Update by the command

sudo update-grub

Then reboot your computer.

sudo reboot

## Bluetooth

sudo apt install bluez-tools
bt-device - a bluetooth device manager

options snd-hda-intel model=Galaxy Buds (E356)

## Different wallpapers on all monitors

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

flatpak install flathub org.gabmus.hydrapaper
flatpak run org.gabmus.hydrapaper