Install with:

1sudo apt install at

Enable the daemon service with:

1sudo systemctl enable --now atd

Then jobs can be specified with absolute time, such as:

1at 16:20

1at noon

1at midnight

1at teatime

Type in your command, e.g.:

1touch /tmp/$FILE.txt

The jobs can also be specified relative to the current time:

1at now …

You need about a dozen commands to move around Linux. After that, you look up the rest as you go. Don't worry about understanding any of it, just type it in and the habit forms pretty quickly.

You start in a dark room. You want to know where you are by printing out your working 'directory' (i.e. 'location'):

1pwd

Have …

Show system time:

1date

Show hardware time:

1sudo hwclock -r

Change system time to match hardware time:

1sudo hwclock --hctosys

Change hardware time to match system time:

1sudo hwclock --systohc

Manually set the hardware time to a specified date:

1sudo hwclock --set --date="8/25/19 13:30:00"

Normal Date

1date …

If statements

Test statement equality as so:

1
2read t1
3read t2
4if test $t1 != $t2; then
5	echo 'variables do not match'
6else
7	echo 'variables match'
8fi
9exit 0

Case Structure

These deal with multiple states rather than forking conditions.

Example:

 1
 2#!/bin/bash
 3
 4# Simple case demonstration …

Cronie

The cronie program is also known as crond.

Install

1sudo apt search -n ^cron

Once installed, search for the service name, and start it.

1sudo systemctl list-unit-files | grep cron
2sudo systemctl enable --now $NAME

Usage

Show your current crontab:

1crontab -l

You can put this in a file and edit it:

1crontab -l …

Compose a statement for execution.

1x='echo $y'
2echo $x
3y=dragon
4eval "$x"

The results remain in the current shell, unlike sub-shells.

1b=basilisk
2sh -c 'echo $b'
3eval "g=goblin"
4echo $g

A hard link is one file which exists in multiple locations.

Each file has an ID, which is kept on the hard disk's partition. Each hard link has the same ID, because they are the same file. This ID is called the 'inode'.

Create a file, and a hard link:

1fortune > $file_1
2mkdir -p x/y/z/
3ln $file_1 x/y/z/$file_2 …

Living Space

Kernel modules live in lib/modules/$(uname -r)

Change

Load them with

1sudo modprobe ath9k

Or remove one with

1sudo modprove uvcvideo

The PC's irritating speaker beep can be really annoying. Disable it with:

1sudo modprobe -r pcspeaker

Permanently disable a module by blacklisting it in /etc/modprobe.d:

1 …

If you want to kill a program in a graphical environment, open a terminal and type:

Graphical Programs

1xkill

Then click on the application which you want to kill.

All Programs

To kill a program, find it with:

1pgrep discord

This will give you the UUID, e.g. 19643.

Kill the program with:

1kill 19643

Types of Kill

To …

There are two types:

• Soft links
• Hard links