SSH tunnel

ssh -N -R 5555:1.2.3.4:666 user@hostname

• 5555 is a port you make up
• 666 is the port to which you are forwarding
• 1.2.3.4 is the IP of the target host to which you are fowarding
• hostname is the host where port 5555 will be made available
• you run this command on a third machine (e.g. your local host)

This results in  hostname:5555  getting forwarded to  1.2.3.4:666

Useful bash flags for scripts verbose trace expand error exit

Useful flags:
set -v # "verbose" - echo commands

set -x # "xtrace" - like verbose but expands commands

set -e # "errexit" - abort script at first error

set -u # "nounset" - strict mode: undefined variable causes an exit

Long format:

set -o verbose

Bash "strict mode":
#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

(source, source)