Linux Distributions:

• Debian: upstream for Ubuntu, Linux Mint, and others. Purely open source focus on stability.
• Red Hat: CentOS Stream is very close to Red Hat Enterprise Linux.
• OpenSUSE

How to Setup sudo:

1. Use su to switch to root
2. Go to /etc/sudoers.d , edit the file using visudo, and add the line:
   {username} ALL=(ALL:ALL) ALL
   The line has the following meaning:
   • {username} ALL=(ALL:ALL) ALL: Rule applies to all hosts
   • {username} ALL=(ALL:ALL) ALL: The user can run commands as all users
   • {username} ALL=(ALL:ALL) ALL: The user can run commands as all groups
   • {username} ALL=(ALL:ALL) ALL: The rules are applied to all commands.
3. Add the following to PATH=$PATH:/usr/sbin:/sbin to the .bashrc file in the home directory.

Common Bash Redirectors:

• >: Redirects STDOUT. If redirection is to a file, the current contents of that file are overwritten.
• »: Redirects STDOUT in append mode. If output is written to a file, the output is appended to that file.
• 2>: Redirects STDERR.
• 2>&1: Redirects STDERR to the same destination as STDOUT.
• <: Redirects STDIN.

Filesystem Tree Layout

User Environment

Account Management

Package Management

Version Control with Git

Programs in Linux

Memory Management

I/O Management

Containers

Disk Management

Kernel Management

Network

Using Cron

• Be careful of the difference between system-wide cron(Runs by root) and user cron(run by users)
• Crontabs are at /etc/crontab

Cronline:

* * * * * <command>

1: Minute 2: Hour 3: Day of the month 4: Month of the year 5: Day of the week Use / to indicate repeat of every time interval. To add a new cronjob. Run:

crontab <filename>