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SSH cheatsheet#

Access charm's web UI when they are deployed on multipass#

MULTIPASS_VM_IP="10.43.8.206"  # From `multipass list`
GRAFANA_UNIT_IP="10.1.166.80"  # From `juju status`
GRAFANA_WORKLOAD_PORT="3000"   # From familiarity with the app

sudo ssh -o "UserKnownHostsFile=/dev/null" -o "StrictHostKeyChecking no" \
  -i /var/snap/multipass/common/data/multipassd/ssh-keys/id_rsa \
  ubuntu@$MULTIPASS_VM_IP \
  -L 8080:$GRAFANA_UNIT_IP:$GRAFANA_WORKLOAD_PORT

sudo sshuttle -r ubuntu@10.196.135.115 10.1.27.0/16 \
  --ssh-cmd 'ssh -o "UserKnownHostsFile=/dev/null" -o "StrictHostKeyChecking no" \
  -i /var/snap/multipass/common/data/multipassd/ssh-keys/id_rsa'

Set up SSH server#

Install ssh server on the server and back-up the config file: 

sudo apt install openssh-server
sudo cp /etc/ssh/sshd_config{,.bak}

Update config (/etc/ssh/sshd_config): 

-#PermitRootLogin prohibit-password
+PermitRootLogin no

-#PasswordAuthentication yes
+PasswordAuthentication no

Test the config before reloading: 

sudo sshd -t -f /etc/ssh/sshd_config

Reload: 

sudo systemctl reload ssh

Generate key pair on the client: 

ssh-keygen -t rsa -b 4096 -f ~/secrets/tailscale-ssh -C ""

  • .rw------- ~/secrets/tailscale-ssh (private key)
  • .rw-r--r-- ~/secrets/tailscale-ssh.pub (public key)

Copy the public key to the server and update the list of authorized keys 

cat /tmp/tailscale-ssh.pub >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

From the client, log in to the server: 

ssh -i ~/secrets/tailscale-ssh \                                                                                                                                                                   [±main ●●●]
  -o "UserKnownHostsFile=/dev/null" \
  -o "StrictHostKeyChecking no" \
  user@remote

Generate SSH key for GitHub#

ssh-keygen -t ed25519 -C "82407168+sed-i@users.noreply.github.com" -N "" -f github_ssh

Refs: 1, 2 3

Then, 

git config --global gpg.format ssh
git config --global user.signingkey /PATH/TO/github_ssh.pub
git config --global commit.gpgsign true  # sign all commit by default (optional)