Ubuntu

Users & Groups

Add a new user to the machine on a Linux OS

# Default shell /bin/sh
adduser USER

# Custom shell /usr/bin/zsh
adduser --shell /usr/bin/zsh

Add a USER to the sudo group
```
usermod -aG sudo USER
```

Delete a user from the machine

# Keep a backup of the user's home directory, stored in the pwd
deluser USER --backup --remove-all-files

Delete a group from the machine
```
delgroup GROUP
```
Change the machine's hostname
```
hostnamectl set-hostname HOSTNAME
```

Change a user's username

# Short form
usermod USER -l NEW_USERNAME -md NEW_HOME_FILEPATH
# Long form
usermod USER --login NEW_USERNAME --move-home --home NEW_HOME_FILEPATH

Change a group's name

# Short form
groupmod GROUP_NAME -n NEW_NAME

# Long form
groupmod GROUP_NAME --new-name NEW_NAME

Change a user's information on a Linux OS

# [ Linux ]

# Short form
chfn USER -f "Austin Traver"
# Long
chfn USER --full-name "Austin Traver"

View which groups the active user is associated with:
```
groups
```
The output is similar to the following:
```
staff admin
```
The first group listed in the output is the user's primary group.
View which groups a particular user belongs to:
```
groups USER
```
The output is similar to the following:
```
USER : USER cdrom floppy audio video admin netdev
```
Where USER is the name of the user provided in the command.
Change the owner that a particular file belongs to:
```
chgrp OWNER FILE
```
Where OWNER is the owner of the file located at the filepath FILE
Change the group that a particular file belongs to:
```
chgrp GROUP FILE
```
Where GROUP is the group of the file located at the filepath FILE

Note: If you need to change both the owner and group associated with a given file, you change the group first! If you change the owner first, you will have lost the permissions required in order to change the group a file belongs to. As a consequence, you will no longer be able to change the group.

Printing system information

View the current system's hardware information:
```
lshw
```
Print the number of processors on the system:
```
nproc
```

Update alternatives for common commands

Ubuntu keeps track of the default programs by maintaining a list of symbolic links, under /etc/alternatives directory. Each entry here is a shortcut points to the actual program, which may have more than one option (i.e. alternatives).

List all existing entries of known alternatives
```
update-alternatives --get-selections
```
<pre><code>... java auto /usr/lib/jvm/java-11-openjdk-amd64/bin/java javac auto /usr/lib/jvm/java-11-openjdk-amd64/bin/javac ... </code></pre>
List all possible alternatives of a existing entries
```
update-alternatives --list java
```
<pre><code>/usr/lib/jvm/java-11-openjdk-amd64/bin/java /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java </code></pre>

Add an unlisted entry to the set of possible alternatives

# Note: you'll still need to specify an entry using '--set'/'--config'
update-alternatives --install /usr/bin/editor editor /usr/bin/vi 80

Interactivelly set a particular entry as the alternative
```
update-alternatives --config java
```
Programmatically set a particular entry as the alternative
```
update-alternatives --set editor /usr/bin/nvim
```

Apt

Install the development tools package
```
apt install -y build-essential
```
Install the manual pages about using GNU/Linux for development:
```
apt install -y manpages-dev
```

Snap

Installing Snapcraft

apt install -y snapd
snap set system refresh.retain=2

Finding the specific version of a package
```
snap info PACKAGE
```
Where PACKAGE is a name, such as cmake

Installing a specific version of a package

snap install cmake --channel=3.17/stable --classic

SMB

Installing SMB server on Ubuntu

Install the samba package from apt

apt update
apt install -y samba samba-common-bin smbclient cifs-utils

[sambashare]
path = /home/USER/DIR
read only = no
browsable = yes
comment = hello world

service smbd restart
ufw allow samba
smbpasswd -a USER

C/C++

Install GCC v7 through v10

apt install -y build-essential g{cc,++}-{7..10}
for v in {7..10}; do
    update-alternatives \
    --install /usr/bin/gcc gcc /usr/bin/gcc-${v} $((${v}*10)) \
    --slave /usr/bin/g++ g++ /usr/bin/g++-${v} \
    --slave /usr/bin/gcov gcov /usr/bin/gcov-${v}
done

Java

Installing the OpenJDK implementation of Java SE:
- Using Apt
```
apt install -y default-jre default-jdk
```
- Using Snapcraft
```
snap install openjdk
```

Go

Installing the Go programming language

Using Apt

add-apt-repository -y -u ppa:longsleep/golang-backports
apt install -y golang

Using Snapcraft
```
snap install go --classic
```

Python

Installing the Python programming language

apt install -y software-properties-common
add-apt-repository -y -u ppa:deadsnakes/ppa
apt install -y python3

Setting the command python to use Python 3:

update-alternatives --install /usr/bin/python 'python' /usr/bin/python3 100 --slave /usr/bin/pip pip /usr/bin/pip3

LLVM

Installing LLVM the risky way

# sudo -i
wget -O - https://apt.llvm.org/llvm.sh | bash -

GitHub

Installing the GitHub CLI

Using Snap

snap install gh
snap connect gh:ssh-keys

Using APT

apt-key adv --keyserver 'keyserver.ubuntu.com' --recv-key 'C99B11DEB97541F0'
add-apt-repository -y -u 'https://cli.github.com/packages'
apt install -y gh

NodeJS

Installing NodeJS using Snapcraft
```
snap install node --classic
```

Installing NodeJS the risky way

# sudo -i
curl -sL https://deb.nodesource.com/setup_15.x | bash -

AWS

Installing the AWS CLI from Pip

apt install python3-pip
pip3 install awscli --upgrade --user

Installation

Installing Ubuntu the hard way

On macOS:

hdiutil convert ~/Downloads/ubuntu.iso -format UDRW -o ~/Downloads/ubuntu.img
mv ~/Downloads/ubuntu.img.dmg ~/Downloads/ubuntu.img
diskutil list
diskutil unmount /dev/disk2
sudo dd if=${HOME}/Downloads/ubuntu.img of=/dev/disk2 bs=1m
diskutil eject /dev/disk2

Using privileged admin account open up terminal or your favorite text editor and edit the configuration file /etc/gdm3/custom.conf

Change the following snippet from

Before you begin editing, your configuration might look like this:

[daemon]
# Uncoment the line below to force the login screen to use Xorg
#WaylandEnable=false

# Enabling automatic login
#  AutomaticLoginEnable = true
#  AutomaticLogin = USERNAME

Change the file so that it instead looks like this:

[daemon]
# Uncoment the line below to force the login screen to use Xorg
#WaylandEnable=false

# Enabling automatic login
AutomaticLoginEnable = true
AutomaticLogin = USERNAME

You will need root/administrator privileges to perform this operation. Uncommenting the above lines will enable automatic login for the linuxconfig user. Change the username to suit your needs.

Snap Packages

Ubuntu is migrating away from using Debian's Apt to manage packages, and toward using Canonical's Snapcraft

They wrote an article titled How to keep your Linux disk usage nice and and tidy where I learned you can reduce the number of prior package versions that Snapcraft keeps, which by default, is three.

snap set system refresh.retain=2

Distribution Upgrades

Ubuntu 20.04 "Focal Fossa" has just released, so I thought I'd write a guide on how to upgrade.

Upgrading to the latest Ubuntu distro:

Sign in to the root user
```
sudo -i
```
Update the /etc/apt/sources.list, replace any entries of bionic or eoal with focal
```
sed -i 's/bionic/focal/g' /etc/apt/sources.list
```

Run the apt commands below

apt update
apt upgrade
apt full-upgrade
apt install -y update-manager-core
reboot
do-release-upgrade -d

Verify successful upgrade by checking the current distribution number
```
lsb_release -a
```

Google Cloud SDK

Installing a Snap package for the Google Cloud SDK:
```
snap install google-cloud-sdk --classic
```

Vim

Installing NeoVim
```
snap install neovim --classic
```

PowerShell

For more information, see Installation via Package Repository in the PowerShell documentation.

# Install pre-requisite packages.
sudo apt update && sudo apt install -y \
    wget \
    apt-transport-https \
    software-properties-common \

# Download the Microsoft repository GPG keys
wget -q https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb

# Register the Microsoft repository GPG keys
sudo dpkg -i packages-microsoft-prod.deb

# Update the list of packages after
# we added packages.microsoft.com,
# then install PowerShell
sudo apt update && sudo apt install -y powershell

Mounting Files

If you are running Ubuntu from within Windows Subsystem for Linux, you can mount a remote filesystem on another host, such as a host running macOS, with the hostname HOENN, and a share named Macintosh HD, as follows:

mkdir /mnt/s
mount -t drvfs '\\HOENN\Macintosh HD' /mnt/s

Alternatively, you can mount the volume as a network drive within Windows in the File Explorer, and run the following command to mount the network drive:

mkdir /mnt/m
mount -t drvfs 'M:\' /mnt/m

Convert SVG to PNG

Install librsvg, which is built by GNOME

If you want to convert example.svg into a 1024x1024 PNG file, you have a few choices. These are ordered from best to worst.

Using librsvg:

# If necessary
sudo apt install librsvg2-bin

rsvg-convert -w 4096 -h 4096 example.svg -o example.png