Linux/Ubuntu - Basics

some frequently used commands, basic security, and tools.

🐧 Linux Ubuntu Basics

If you're new to Linux, this page is your starting point. Here are essential commands you'll use often while managing a node or validator server (VPS) on Ubuntu.

🧭 Navigation

pwd                      # Show current working directory
ls                       # List files and folders
ls -l                    # Long listing (with permissions, size, date)
ls -a                    # Show hidden files (starting with .)
cd folder-name           # Change into a folder
cd ..                    # Go up one level
cd ~                     # Go to home directory
cd /path/to/folder       # Go to specific path

🗃 Creating, Moving, Deleting Files & Folders

mkdir folder-name             # Create a folder
mkdir -p folder/subfolder     # Create nested folders

touch file.txt                # Create an empty file
cp file1.txt file2.txt        # Copy a file
mv oldname.txt newname.txt    # Rename or move a file
rm file.txt                   # Delete a file
rm -r folder-name             # Delete a folder and its contents

📝 Viewing & Editing Files

cat file.txt                  # Show file content
nano file.txt                 # Open and edit a file
less file.txt                 # Scroll through long files (q to quit)
head file.txt                 # Show the first 10 lines
tail file.txt                 # Show the last 10 lines
tail -f file.txt              # View log output in real-time

🔍 Searching and Finding

grep "word" file.txt          # Search for a word in a file
find . -name "*.log"          # Find all .log files in current folder
which binary-name             # Find location of a program

🧰 System & Package Management

sudo apt update               # Update available packages
sudo apt upgrade              # Upgrade installed packages
sudo apt install packagename  # Install a new package
sudo apt remove packagename   # Remove a package
sudo apt autoremove           # Remove unused packages

🔐 Permissions and Executables

chmod +x file.sh              # Make a file executable
chmod 755 script.sh           # Set specific permissions
chown user:group file         # Change file ownership

🔁 Process & System Monitoring

top                          # View running processes
htop                         # Better version of top (install with apt)
ps aux | grep binary         # Find running process
kill PID                     # Stop a process by PID
df -h                        # Show disk usage
free -m                      # Show memory usage
uptime                       # Show system load and uptime

📦 Archive & Compression

tar -xvf file.tar            # Extract .tar files
tar -xzvf file.tar.gz        # Extract .tar.gz files
tar -xvJf file.tar.xz        # Extract .tar.xz files
unzip file.zip               # Extract .zip files

📡 Network Commands

curl ifconfig.me             # Show public IP
ping google.com              # Check network connection
netstat -tuln                # List listening ports (install: net-tools)
ss -tuln                     # Modern alternative to netstat
lsof -i :26656               # Check what's using port 26656

🎬Running in the Background with screen

Task
Command

Install screen

sudo apt install screen -y

Start screen

screen -S nodename

Detach screen

Ctrl + A then D

Reattach screen

screen -r nodename

List sessions

screen -ls

Kill session

screen -X -S name quit

🧹 Useful Shortcuts

!!                           # Repeat last command
!apt                         # Run last command starting with 'apt'
history                      # Show command history
clear                        # Clear the terminal screen
Ctrl + C                     # Stop a running command
Ctrl + D                     # Logout or close terminal session
Tab                          # Autocomplete file/folder names

🔐 Security Basics

Running a node means your server is connected to the internet 24/7. That also means it's open to attacks if you're not careful.

In this section, we'll go through basic but important steps to protect your VPS or bare-metal server. These are simple things that every node operator should do.

1. Use a Strong Password or SSH Key🔑

Avoid using weak passwords. The best way to connect to your server is with an SSH key, not a password.

To generate a key (on your local machine):

ssh-keygen -t rsa -b 4096

Then copy it to your server:

ssh-copy-id user@your-server-ip

Disable password login:

sudo nano /etc/ssh/sshd_config

Change or make sure these lines are set:

PasswordAuthentication no
PermitRootLogin no

Then restart SSH:

sudo systemctl restart ssh

2. Set Up a Basic Firewall (UFW) 🛡️

Allow only the ports you need:

sudo apt install ufw -y
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw allow 26656         # Example: P2P port for Cosmos-based chains
sudo ufw allow 26657         # Example: RPC port (optional or restrict)
sudo ufw enable

You can check status:

sudo ufw status

3. Fail2Ban – Protect SSH from Brute Force 🚫

sudo apt install fail2ban -y

This helps block IPs that try to brute-force into your server.

4. Remove Unused Packages🧼

Keep your system clean:

sudo apt autoremove -y

5. Keep the System Updated🛠️

Regular updates help fix known security issues:

sudo apt update && sudo apt upgrade -y

6. Optional: Monitor Login Activity📋

Check who logged in and when:

last

Check failed login attempts:

sudo cat /var/log/auth.log | grep "Failed"

🧠 Final Tips

  • Don’t run everything as root user.

  • Only open the ports you really need.

  • Use a separate user (e.g. nodeuser) to run your validator.

  • Always secure your mnemonic / private key — don’t keep it on the server!

📦 The most frequently installed and used dependencies for operating a crypto node or validator.

When running a crypto node or validator — especially in Cosmos, Substrate, or Ethereum-based chains. you’ll often need to install essential tools and libraries to compile code, run the software, or manage the server.

⚙️ Essential System Packages

Install these on most Ubuntu 20.04/22.04 servers:

sudo apt update && sudo apt upgrade -y
sudo apt install -y \
  curl wget git build-essential \
  jq make gcc tmux unzip \
  lz4 net-tools htop \
  ca-certificates software-properties-common

🧰 Go (Golang)

Most Cosmos SDK chains require Go.

# Replace with the latest stable version if needed
wget https://golang.org/dl/go1.22.2.linux-amd64.tar.gz
sudo rm -rf /usr/local/go
sudo tar -C /usr/local -xzf go1.22.2.linux-amd64.tar.gz

# Add to PATH (for bash or zsh)
echo "export PATH=\$PATH:/usr/local/go/bin:\$HOME/go/bin" >> ~/.bashrc
source ~/.bashrc

🔎 Verify:

go version

🐍 Python (Optional for Some Tooling)

sudo apt install python3 python3-pip -y

🪙 Rust (Common for Substrate chains)

curl https://sh.rustup.rs -sSf | sh
source $HOME/.cargo/env

🔎 Verify:

rustc --version

📚 Optional But Useful Tools

Tool
Purpose
Install Command

screen

Run processes in background

sudo apt install screen

htop

Visual system resource monitor

sudo apt install htop

jq

JSON parser used in scripts

sudo apt install jq

lz4

For snapshot decompression

sudo apt install lz4

unzip

Extract .zip files

sudo apt install unzip

net-tools

Port scanning and IP checks

sudo apt install net-tools

fail2ban

Basic security for SSH brute force

sudo apt install fail2ban

🐙 Using Git and Github

Git is the version control tool used to manage code. GitHub is the website where most crypto node projects host their source code.

📥 Cloning a Repository

git clone https://github.com/project/repo.git
cd repo

This will download the entire codebase to your server.

📈 Checking the Status

git status            # Show file changes and branch info
git remote -v         # Show GitHub repo links
git branch            # Show current branch

🔄 Pulling Updates

git pull origin main

Use this to get the latest code updates from GitHub (for example, when a new binary is released).

If you’re unsure which branch the project uses:

git branch -r         # Show remote branches

🧪 Switching Branches

git checkout testnet-branch-name

Useful when a project has separate branches for testnet, mainnet, or dev environments.

🔧 Building After Pull

After pulling new code, you often need to rebuild:

make install
# OR
go build -o binary-name .

🧹 Cleaning Build Files (Optional)

make clean

🆕 Creating Your Own Git Repo (Advanced)

If you're building your own tooling or automation scripts:

git init                          # Start a new Git repo
git remote add origin <url>       # Connect to GitHub
git add .                         # Stage all files
git commit -m "initial commit"    # Save changes
git push -u origin main           # Push to GitHub

🧹 Uninstalling Apps or Binaries

Sometimes you need to remove a binary or app from your system — maybe the node software has changed, or you're switching networks. Here's how to safely uninstall things on Ubuntu.

1. Uninstall Software Installed via apt 📦

sudo apt remove packagename
sudo apt purge packagename         # Also remove config files
sudo apt autoremove                # Remove unused dependencies

📌 Example:

sudo apt remove golang-go
sudo apt purge tmux

2. Remove Go Binaries Installed from Source 🧱

If you built a node binary with make install, it usually ends up in $HOME/go/bin.

which binary-name                  # Find path
rm $(which binary-name)           # Remove the binary

📌 Example:

rm $(which seid)

Or manually:

rm ~/go/bin/binary-name

3. Delete the Source Code Folder 📁

If you cloned from GitHub and no longer need the code:

rm -rf ~/repo-folder

📌 Example:

rm -rf sei-chain

4. Clear Configuration & Data (if needed) 🧼

Most blockchain nodes store their data and config in a .chain folder (e.g. .sei, .gaia, .celestia-app).

rm -rf ~/.chain-folder

📌 Example:

rm -rf ~/.sei

5. Remove systemd Service (if used)🧹

If you used systemd to manage your node:

sudo systemctl stop nodename
sudo systemctl disable nodename
sudo rm /etc/systemd/system/nodename.service
sudo systemctl daemon-reload

✅ That’s it! Your system is now clean.

Tip: Keep a record of everything you installed for each node in case you need to clean up or reinstall later.

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