Terminal Emulation
https://en.wikipedia.org/wiki/Terminal_emulator
tmux
Share session
# Create session
tmux -S /tmp/tmsession
chmod 777 /tmp/tmsession
# Connect
tmux -S /tmp/tmsession attach
Keyboard shortcuts
| Shortcut | Description |
|---|---|
| C-b ? | List keybindings |
| C-b “ | Split screen horizontally |
| C-b % | Split screen vertically |
| C-b arrow | Switch pane |
| C-b (held) arrow | Change size of pane |
| C-b ; | Switch to last active pane |
| C-b x | Kill pane |
| C-b c | New window |
| C-b n | Next window |
| C-b p | Previous window |
| C-b & | Kill window |
| C-b PgUp/PgDn | Scroll mode |
| C-b . | Move window |
Adding to tmux buffers from shell
echo "hello" | tmux loadb -
tmux saveb - | sed 's,hello,hi,'
SSH
Generating a new key
# Generate a new RSA keypair
ssh-keygen -t rsa -b 4096 -C "<username> generated <date>" -f id_rsa
# Generate a new ed25519 keypair
ssh-keygen -t ed25519 -C "<username> generated <date>"
Getting key fingerprint
ssh-keygen -lf .ssh/id_rsa.pub
Security notes
General
- Use protocol 2
Client
- If using ssh-add (ie the ssh-agent), also use
-cand-t <seconds>arguments, and use an askpass program to confirm connections - Use HashKnownHosts to obscure which hosts you connect to. To retroactively do this on an existing file
ssh-keygen -H
Server
- Use something like fail2ban, and rate limit incoming connections
IgnoreRhosts yes
RhostsRSAAuthentication no
HostbasedAuthentication no
# Don't use tunneled cleartext passwords
PubkeyAuthentication yes
PasswordAuthentication no
PermitEmptyPasswords no
ChallengeResponseAuthentication no
# Disable root user login
PermitRootLogin no
UsePam yes
# Disable X11 forwarding
X11Forwarding no
# Disable TCP forwarding (unless you *actually* need it)
AllowTcpForwarding no
# Lock down to specific group of users
AllowGroup ssh_users
HostbasedAuthentication no
PermitUserEnvironment no
StrictModes yes
UsePrivilegeSeparation yes
Troubleshooting
As silly as some of these seem, I’ve seen them all apply at one point or another.
Client-side
- Are you using the correct key?
- Confirm this using the -i flag
- Have you ordered your flags correctly?
- Confirm this by looking at the man page - order is important!
- Is your username correct?
- Have you confirmed you’re trying to connect to the right box?
- Is the DNS record connect? is your SSH client correctly resolving to that address?
- Do you need to have a VPN turned on?
- Is your routing correct?
- Does the fingerprint match?
Server-side
- Is sshd running?
- Is the firewall open?
- Are the logs showing any connections?
DEC VTs
Terminal Emulators
Alacritty
XTerm
Comes with X Windows
| Command | Keys |
|---|---|
| Paste clipboard | shift + insert |
| Main menu | ctrl + left click |
| Font menu | ctrl + right click |
Using bash to make TUIs
https://github.com/dylanaraps/writing-a-tui-in-bash
ncurses
Notcurses
A much prettier (albeit less compliant) TUI library
GNU Screen
# Reattach a terminal
screen -r
# Attach to a non-detached session (pair-programming)
screen -x
# Share session
screen -d -m -S (session name)
screen -x (session name)
Keyboard shortcuts
| Shortcut | Command | Description |
|---|---|---|
| C-a ” | windowlist -b | list all windows |
| C-a C-a | other | go to previous screen |
| C-a C-d | detach | detach from screen back to the terminal |
| C-a k | kill | kill window |
| C-a H | log | log the current window |
| C-a C | new window |
Scrollback
C-a :
scrollback <lines>
C-a [
Minicom
Attach to a serial console
# ensure that the dev node has correct permissions
minicom -s
# select "Serial port setup"
# save
Telnet
Neat things to connect to
- https://www.livingcomputermuseum.org
- http://www.telnet.org/htm/places.htm
- towel.blinkenlights.nl - ASCII Star Wars
- nyancat.dakko.us - Nyan cat