Notes

SSH

Setup host

In ~/.ssh/config

Host HOST
    HostName SERVERIP
    User SERVERUSER

Generate key pair

ssh-keygen -t ed25519 -C "COMMENT"

Leave blank to take default for the prompt Enter file in which to save the key (/home/USERNAME/.ssh/id_ed25519).

Then, you can enter a passphrase for your key. To keep it simple while learning, we will not add one now. Press enter twice to not use a passphrase. But you should use a passphrase when you work with real servers!

Add the public key to the server

ssh-copy-id -i ~/.ssh/id_ed25519.pub HOST

Connect

ssh HOST

Config on server

Very important for security! Only after adding the public key to the server!

WARNING ⚠️ :

Verify that you are only asked for the passphrase of the SSH key before continuing in this section!

If you are asked for the password of the user on the server when connecting, then the authentication with a key did not work. Therefore, don't set PasswordAuthentication no! Fix the issue with the key authentication first. Otherwise, you will be locked out of the server! ⚠️

In /etc/ssh/sshd_config on the server:

Uncomment line with PasswordAuthentication and set it to PasswordAuthentication no

Save and exit, then run:

sudo systemctl restart sshd

If you are locked out after running this command, then you did not take the warning above seriously!

Rsync

From server:

rsync -Lahz HOST:SRC_PATH DEST_PATH

To server:

rsync -Lahz SRC_PATH HOST:DEST_PATH

Options:

-a, --archive: Set of useful options to preserve permissions, use recursive mode, etc.
-h, --human-readable: Output number in a human-readable format.
-z, --compress: Use compression.
--partial: Continue after interruption.
-L, --copy-links: Copy links.
-v, --verbose: Show more infos.
--delete: Delete files from DEST_PATH if they don't exist on SRC_PATH anymore. Use with caution!!!

Systemd

Check status of a service:

sudo systemctl status SERVICENAME

Enable service:

sudo systemctl enable SERVICENAME

Start service:

sudo systemctl start SERVICENAME

Enable and start service at the same time:

sudo systemctl enable --now SERVICENAME

Disable service:

sudo systemctl disable SERVICENAME

Stop service:

sudo systemctl stop SERVICENAME

Disable and stop service at the same time:

sudo systemctl disable --now SERVICENAME

Firewalld

Install and enable firewalld:

sudo dnf install firewalld
sudo systemctl enable --now firewalld

View open ports and services:

sudo firewall-cmd --list-all

Open ports 80 (http) and 443 (https):

sudo firewall-cmd --add-service http
sudo firewall-cmd --add-service https
sudo firewall-cmd --runtime-to-permanent

or:

sudo firewall-cmd --add-port 80/tcp
sudo firewall-cmd --add-port 443/tcp
sudo firewall-cmd --runtime-to-permanent

Podman

# Search for image
podman search python

# Pull image
podman pull docker.io/library/python:latest

# See pulled images
podman images

# Run container and remove it afterwards
podman run -it --rm docker.io/library/python:latest bash

# Create network
podman network create NETWORKNAME

# Create container
podman create \
    --name CONTAINERNAME \
    --network NETWORKNAME \
    -e ENVVAR="Some value for the demo environment variable" \
    --tz local \
    docker.io/library/python:latest

# Start container
podman start CONTAINERNAME

# Enter a running container
podman exec -it CONTAINERNAME bash

# Stop container
podman stop CONTAINERNAME

# Generate systemd files
podman generate systemd --new --files --name CONTAINERNAME

# Create directory for user's systemd services
mkdir -p ~/.config/systemd/user

# Place service file
mv container-CONTAINERNAME.service ~/.config/systemd/user

# Activate user's service (container)
systemctl --user enable --now container-CONTAINERNAME

Keep user's systemd services live after logging out:

sudo loginctl enable-linger USERNAME

Options:

-v, --volume: SRC_PATH:DEST_PATH:L. Label should be one of z, z,ro, Z or Z,ro.
-p, --publish: SERVER_PORT:CONTAINER_PORT

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