Category: linux

Preset Tmux Windows

Posted on by Bian Xi Leave a Comment on Preset Tmux Windows

Preset Tmux Windows

To preset Tmux windows, following script can be used. It also issues ssh command to host which has same name as window name.

#!/bin/bash

WINDOWS="window_name1 window_name2 window_name3"

for each in $WINDOWS
do
  if ! tmux has-session -t 0:$each; then
    tmux new-window -n $each ssh $each
  fi
done

tmux attach

References

Restore tmux session after reboot
Check If Window With a Specific Name Exists. If It Does Attach to it; Otherwise Create it and Run Command?

Tmux vs Screen

Posted on by Bian Xi Leave a Comment on Tmux vs Screen

Tmux vs Screen

The unix command screen and tmux have similar goal, but tmux is more complex than screen.

Quick Tips

In order to start using tmux without worrying about forgetting keys, remember follows one after another.

  • Help using key Ctrl+b ?
  • Detach using key Ctrl+b d
  • Resume using command tmux a
  • Create window using command Ctrl+b c
  • Navigate windows using key Ctrl+b w, then arrow keys
  • Rename window using key Ctrl+b ,
  • Status bar has window name and <id>
  • Switch window using key Ctrl+b <id>

Commands

screen tmux
Startup screen tmux
Starting Named Session screen -S session_name tmux new -s session_name
List running session screen -ls tmux ls
Reattach screen -r
Reattach by id screen -r <id> tmux attach-session -t <id>

Keys

screen tmux
Help Ctrl+a ? Ctrl+b ?
Create a new shell (without window) Ctrl+a c
Switch to next shell Ctrl+a space
Switch to previous shell Ctrl+a backspace
Create a new window (with shell) Ctrl+b c
List all shells Ctrl+a "
Choose window from a list Ctrl+b w
Switch to N'th shell Ctrl+a <n>
Switch to N'th window Ctrl+b <n>
Rename the current window Ctrl+a A Ctrl+b ,
Split current region horizontally into two regions Ctrl+a S Ctrl+b %
Split current region vertically into two regions Ctrl+a | Ctrl+b "
Switch the input focus to the next region Ctrl+a tab Ctrl+b o
Toggle between the current and previous windows Ctrl+a Ctrl+a Ctrl+b ;
Close all regions but the current one Ctrl+a Q
Close the current region Ctrl+a X Ctrl+b x
Detach from session Ctrl+a d Ctrl+b d
Sent Ctrl+a to region Ctrl+a a

Customize

screen

Customization can be done in /etc/screenrc and ~/.screenrc. Sample of contents is shown below.

# Turn off the welcome message
startup_message off

# Disable visual bell
vbell off

# Set scrollback buffer to 10000
defscrollback 10000

# Customize the status line
hardstatus alwayslastline
hardstatus string '%{= kG}[ %{G}%H %{g}][%= %{= kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B} %m-%d %{W}%c %{g}]'

tmux

Customization can be done in ~/.tmux.conf. Sample of contents is shown below.

# Improve colors
set -g default-terminal 'screen-256color'

# Set scrollback buffer to 10000
set -g history-limit 10000

# Customize the status line
set -g status-fg  green
set -g status-bg  black

References

How To Use Linux Screen
Getting started with Tmux
How to split the terminal into more than one "view"?

SSH Proxy

Posted on by Bian Xi Leave a Comment on SSH Proxy

SSH Proxy

When access remote servers, proxy server/jump host could be a good choice.

Two servers definition

jump_host

This is the proxy server, normally can be in the form of user@proxy_host.

target

This is the target server, has the form of target_user@target_host.

Jump host

This is the most simplest method which uses remote ssh command to login to target server. If just wants to use one SSH server to access another SSH server, run following command

ssh -t <jump_host> ssh <target>

Here -t is to create a pseudo-terminal, otherwise, the remote server could not display message because no tty can be used.

Proxy Jump

This is using SSH building proxy function.

ssh -o "ProxyJump <jump_host>" <target>

Proxy Command

This is to run an external command to build communication. For example, use nc command, and pass two parameters, %h is the target host, %p is the port.

ssh -o "ProxyCommand ssh <jump_host> nc %h %p" <target>

Use ssh client configuration

./ssh/cofig

Instead of using command, ProxyJump and ProxyCommand can be set in ssh client configuration file.

Host <connection_name>
  HostName <target_host>
  User <target_user>
  ProxyCommand ssh <jump_host> nc %h %p

For one server

Host target
  HostName 192.168.1.2
  User user1
  ProxyCommand ssh user2@proxy nc %h %p

For all servers

Host * !proxy
  HostName %h
  User target_user
  # ProxyCommand ssh proxy_user@proxy nc %h %p

/etc/ssh/ssh_config

This is the same as previous example, except it is a global setting.

References

4 ways to SSH & SCP via proxy (jump) server in Linux