SSH and Terminal Workflow¶

SSH is how students connect to remote Ubuntu servers for labs. This page covers key-based login, a simple SSH config file, and terminal habits that reduce mistakes.

1. Verify SSH Works¶

From your local computer:

ssh USERNAME@SERVER_IP_ADDRESS

If this works, exit the server:

exit

2. Generate an SSH Key If Needed¶

On your local computer:

ssh-keygen -t ed25519 -C "your_email@example.com"

Accept the default file path unless your instructor tells you otherwise. Use a passphrase when possible.

3. Copy the Public Key to the Server¶

Preferred method:

ssh-copy-id USERNAME@SERVER_IP_ADDRESS

If ssh-copy-id is not available, print your public key:

cat ~/.ssh/id_ed25519.pub

Then add it to this file on the server:

mkdir -p ~/.ssh
nano ~/.ssh/authorized_keys
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

4. Create an SSH Config Entry¶

On your local computer, edit:

nano ~/.ssh/config

Add:

Host course-server
    HostName SERVER_IP_ADDRESS
    User USERNAME
    IdentityFile ~/.ssh/id_ed25519

Connect with:

ssh course-server

5. Terminal Habits for Labs¶

Habit	Why it matters
Run `pwd` before editing files	Confirms where you are.
Run `ls` or `tree` before deleting files	Avoids accidental deletion.
Use `mkdir -p labs/week01`	Creates repeatable folder structure.
Keep one terminal for notes/output	Makes screenshots and submissions easier.
Copy exact error messages	Troubleshooting depends on exact text.

6. Useful Commands¶

pwd
ls -la
mkdir -p ~/labs
cd ~/labs
history | tail -20

7. Classroom Checkpoint¶

Submit or record:

A successful SSH login using your short host alias, such as ssh course-server.
Output of:
```
whoami
hostname
pwd
```

Troubleshooting¶

Error	Likely Cause	Fix
`Permission denied (publickey)`	Server does not have your public key	Re-run `ssh-copy-id` or check `authorized_keys`.
`Connection timed out`	Firewall, wrong IP, server off	Verify IP, cloud firewall, and UFW rules.
`REMOTE HOST IDENTIFICATION HAS CHANGED`	Server was rebuilt or IP reused	Confirm this is expected, then remove the old key from `~/.ssh/known_hosts`.

Next Step¶

Continue to Git and GitHub Setup.