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ronny abraham b9bddc179a completed ssh sec, added git

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Lesson 05 | Command line Environment

Links
- timestamps
notes

Links

timestamps

notes

topics

job control
terminal multiplexers
dot files / how to configure
work with remote machines

job control

sleep

puts process to sleep for a specified amount of time
exit by typing Ctrl-C

Ctrl-C

sends SIGINT - signal interrupt
man signal will show the list of signals

signals

SIGQUIT: signal sent when we want to quit
SIGTERM: similar to quit but not in term
SIGHUP: when we have processes running but still want to close

pausing

SIGSTOP: pause execution of program
SIGCONT: continue program

python library

use import signal

import signal
def handler(signum, frame):
    printf("signal received")

signal.signal(signal.SIGINT, handler)

the above would catch a Ctrl-C and run it through handler
you use this by catching a Ctrl-C and running any saves or cleanup before exiting

nohup and jobs

allows for a process to continue livign when the terminal is killed

example

sleep put the process to sleep
'&' puts the process in the background
- wont take over the process

nohup sleep 2000 & python somprog.py

jobs

jobs

will show the suspended and running processes in background

how to restart a suspended process
- type 'jobs' to see what there is in this terminal
- the find the jobs number, ie [1] or [2]
- use the 'bg' command
```
bg %1
```

kill command

allows you to send any kind of signal to a job
e.g. "stop" will suspend but not close the job

some commands

HUP: Hang Up
STOP: suspend
KILL: kill it no matter what

Terminal Multiplexer

overview

tmux
lets you create workspaces that you can work in
rearrange the environment
have different settings

core concepts

hierarchy
- sessions
- windows
- panes

dot files

alias

remap a source series of characters to a longer series
alias takes a single argument, ie, do not use spaces
to show what an alias refers to pass the alias to the alias command
- e.g.

~/somedirectory >>> alias myaliasedcommand
myaliasedcommand='ls -lah'

examples

make an alias "ll" for a list command with flags

alias ll="ls -lah"

make an alias for git status

alias gs="git status"

alias to prompt for an override

alias mv="mv -i"

text based configuration 'dot files'

called 'dot files' because they start with a dot
- .bashrc
  - must be in the home directory
- PS1
  - prompt variable for your prompt
  - you can set it in the .bashrc file
  - PS1=" >> "
- .vimrc
  - vim configuration file

tmux

run a session, detach and get back to it later

link

prefix key

Ctl-B

userful commands

detach / attach

Ctl-B , D -> detach
tmux a -> reattach

reattach to most recent session

tmux a

attach to a particular session

list the tmux session
note the index number or name
attach to that index -t (target) ~tmux a -t [INDEX]

kill

kill a session

tmux kill-session -t [INDEX]

kill session from list windows

go into list windows C-b w
highlight the one you want dead
C-b x, it will ask for confirmation

kill ALL sessions

tmux kill-server

kill a pane

C-b x

kill an entire window

C-b &

tmux names session

tmux new -s name

list session

tmux ls

3 layers

layer 1 -> sessions

when you hit tmux you start a new tmux session

layer 2 -> window

when you create a new session, you automatically create an initial window
C-b c :: create a new window in addition to the existing ones
- all windows will be listed in the display line at the bottom
- the * indicates the current
C-b n :: move through your windows
C-b < :: rename window
C-b w :: list all sessions and windows
- you can walk through the list using arrow keys
- enter to switch

kill session

go into list windows C-b w
highlight the one you want dead
C-b x, it will ask for confirmation

layer 3 -> panes

panes exist in windows
add horizontal pane :: C-b %
add vertical pane :: C-b "
switch panes :: C-b [arrow]
show pane index :: C-b q
switch to pane index :: C-b q [index]
change pane size :: C-b [hold Ctl] [arrow]

preselected pay layout

C-b Alt-1-5

terminal emulator - alacritty

very fast
useful for heavy displays like neoviim
vm mode is good for reloading

hint system

pattern recognition of terminal output based on regex
execute commands on those patterns

e.g.

url will be opened in browser

custom actions

shows hints overlay over something recongized
for files or other customized action

themes

black theme

copy mode / vim

treat terminal output as a vim buffer
doesn't support all, but a lot

aliases

you can find good alias lists online

common folder structures

use symlinks to store all your dotfiles in one directory
ln -s [path-to-orig] [path-to-link-location]

~
├─ .bashrc
├─ .vimrc
└─ dotfiles
   ├─ bashrc
   └─ vimrc

ssh

working with remote machines
it is good for opening connections
can execute commands remotely, and piping back the output to the calling shell ssh username@some-ip.com ls -la

ssh keys

typing passwords is inconvenient
use public key encryption
- public, private
- give public key to the server
- whenever you try to authenticate use your private key

create a key

ssh-keygen -o -a -t ed25519

passphrase gives extra protection bc a user of the private key has to give a password
creates
- private key: id_ed25518
- public key: id_ed25519.pub

move the public key to the server

cat ~/.ssh/id_ed25519.pub | ssh username@ip-address.com tee .ssh/authorized_keys

at that point ssh will ask you for the password for the server and then it will put the key where you sent it
'tee' sends standard input both to the screen and to a file (so you can see what is being saved)

ssh-copy-id

does the above but in one command

ssh-copy-id username@ip-address

copy files remotely

scp

scp filename.ext username@ip-address:/path/to/new-filename.ext

rsync

copy a LOT of files remotely
rsync can continue from interrupts

rsync -avP /folder/to/copy/from username@ip-address:/folder/to/copy/to

ssh config

Host hostname User username HostName ip-address IdentityFile ~/.ssh/id_ed25519 RemoteForward 9999 localhost:8888

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