Linux cheatsheet

docker-setup-apt.sh

# Add Docker's official GPG key:
sudo apt-get update
sudo apt-get install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

# Add the repository to Apt sources:
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update

enable_sftp.sh

# 0. Prerequisite: OpenSSH server installed
sudo apt-get update
sudo apt-get install openssh-server

# 1. Configure SSH for SFTP
sudo nano /etc/ssh/sshd_config  # make sure the `Subsystem sftp` line looks like `Subsystem sftp internal-sftp`

# 2. Create a new user group and add users to it
sudo groupadd sftp
sudo usermod -aG sftp <username>

# 3. Configure SFTP access to the new group in the SSH config

sudo nano /etc/ssh/sshd_config

# Add the following to the end of the file:
"
Match Group sftp
    ChrootDirectory /home/%u
    PermitTunnel no
    AllowAgentForwarding no
    AllowTcpForwarding no
    X11Forwarding no
"

# 4. Grant permissions on home folder
sudo chown root:root /home/<username>
sudo chmod 755 /home/<username>

# Check the permissions
sudo ls -ld /home/<username>

# It should look like:
"drwxr-xr-x 3 root root 4096 Aug 19 12:00 /home/<username>"

# 5. Create a subdirectory for uploads, and set the appropriate ownership:
sudo mkdir /home/<username>/uploads
sudo chown <username>:sftp /home/<username>/uploads

# 6. Restart the SSH Service
sudo systemctl restart ssh

# 7. Test the SFTP Connection
sftp <username>@<server-ip>

screens.sh

# Open a screen session, create a new window, and start a shell in that window:
screen

# Start named session:
screen -S session_name

# Reattach screen:
screen -r $SCREEN_ID

# List running screens:
screen -ls

# Shortcuts:
# `Ctrl+a ?`   List screen commands
# `Ctrl+a c`   Create a new window (with shell)
# `Ctrl+a "`   List all window
# `Ctrl+a 0`   Switch to window 0 (by number)
# `Ctrl+a A`   Rename the current window
# `Ctrl+a S`   Split current region horizontally into two regions
# `Ctrl+a |`   Split current region vertically into two regions
# `Ctrl+a tab` Switch the input focus to the next region
# `Ctrl+a`     Toggle between the current and previous region
# `Ctrl+a Q`   Close all regions but the current one
# `Ctrl+a X`   Close the current region
# `Ctrl+a d`   Detach screen

ubuntu.sh

# Create new user
sudo adduser <username>

# Add user to sudoers
sudo usermod -aG sudo <username>

# Check disk usage per use
sudo du -sh /home/* | sort -h