Systems Administrator key topics and quick reference

Updated 15 September 2026 · 2 min read

Systems administrators draw on a large set of facts: which command shows disk usage, which port a service listens on, how much capacity a RAID level gives. The reference tables on this page collect those facts in one place. Use them for daily recall practice, and use the notes below to see how the facts connect in real work.

How this guide was made

Written for this site with AI assistance, then checked automatically before publishing. The topic table, sample questions, worked examples and study plan are generated from this site’s question bank: each worked example is recalculated by separate code, and each sample answer says where it came from.

The guide deliberately states no salaries, grades, pass marks or exam dates. Those change, and they could not be checked here, so take them from the advert itself.

This site is independent and is not affiliated with MIFOTRA or any employer.

Where to spend your study time

The suggested emphasis reflects what this position works with day to day. It is a study guide, not a published exam blueprint.

Area	Suggested emphasis	Questions in the bank	Practise
Hardware and operating systems	23%	961	Hardware & OS
Linux command line	23%	360	In the full bank
Networking fundamentals	15%	2,636	Networking
Cybersecurity	15%	541	Security
IT fundamentals and support practice	15%	484	Hardware & OS
Cloud and emerging technology	8%	188	In the full bank

Using the tables for recall

Test yourself before you read. Cover the description column in the Linux table and say what each command does, then cover the command column and name the command for each task. Do the same with ports. Short daily recall sessions build the instant recognition that exam questions and real incidents both demand.

Quick reference

Linux commands

Command	What it does	Useful option
`ls`	list the contents of a directory	`-l` shows a long listing with permissions, owner and size
`cd`	change the current working directory
`pwd`	print the full path of the working directory
`cp`	copy files or directories	`-r` copies a directory and everything inside it
`mv`	move or rename a file
`rm`	delete a file	`-r` deletes a directory and its contents recursively
`mkdir`	create a directory	`-p` creates parent directories as needed
`cat`	print the whole contents of a file
`less`	page through a file one screen at a time
`head`	show the first lines of a file	`-n` sets how many lines to show
`tail`	show the last lines of a file	`-f` follows the file and prints new lines as they arrive
`grep`	search text for lines matching a pattern	`-i` makes the match case-insensitive
`find`	search a directory tree for files matching criteria
`chmod`	change the permission bits on a file
`chown`	change the user or group that owns a file
`ps`	list running processes	`aux` lists every process on the system with its owner
`top`	show processes and resource use, refreshing live
`kill`	send a signal to a process by PID	`-9` sends SIGKILL, which cannot be caught or ignored
`df`	report free space per mounted filesystem	`-h` prints sizes in human-readable units
`du`	report how much space a directory tree uses	`-sh` gives one human-readable total
`tar`	create or extract an archive	`-x` extracts an existing archive
`systemctl`	control systemd services
`journalctl`	read the systemd journal
`ip`	show or configure network interfaces and routes
`ss`	show open sockets and listening ports
`ping`	test reachability with ICMP echo requests
`traceroute`	show the hops a packet takes to a destination
`dig`	query DNS records
`scp`	copy files between hosts over SSH
`rsync`	synchronise files, transferring only the differences
`sudo`	run a command as another user, normally root
`man`	display the manual page for a command
`script`	record a terminal session to a file
`crontab`	edit the schedule of recurring jobs	`-e` opens the current user’s crontab for editing
`uname`	print system and kernel information	`-a` prints all available system information
`whoami`	print the effective username
`awk`	process text field by field using a pattern-action script
`sed`	edit a stream of text with substitution rules

Ports worth knowing by heart

Service	Port	Transport
FTP data	20	TCP
FTP control	21	TCP
SSH (and SFTP, which runs over it)	22	TCP
Telnet	23	TCP
SMTP	25	TCP
DNS	53	TCP and UDP
DHCP server	67	UDP
DHCP client	68	UDP
TFTP	69	UDP
HTTP	80	TCP
Kerberos	88	TCP and UDP
POP3	110	TCP
NTP	123	UDP
NetBIOS name service	137	UDP
NetBIOS session	139	TCP
IMAP	143	TCP
SNMP	161	UDP
SNMP trap	162	UDP
LDAP	389	TCP
HTTPS	443	TCP
SMB over TCP	445	TCP
SMTPS	465	TCP
Syslog	514	UDP
SMTP submission	587	TCP
LDAPS	636	TCP
IMAPS	993	TCP
POP3S	995	TCP
MSSQL	1433	TCP
Oracle DB	1521	TCP
MySQL	3306	TCP
RDP	3389	TCP
PostgreSQL	5432	TCP
VNC	5900	TCP
HTTP alternate	8080	TCP

RAID levels

Level	Minimum disks	Usable capacity	Survives
RAID 0	2	All disks	No failure
RAID 1	2	One disk	All but one disk
RAID 5	3	n − 1 disks	One disk
RAID 6	4	n − 2 disks	Two disks
RAID 10	4	Half the disks	One disk per mirrored pair

RAID is not a backup. It keeps a system running through a disk failure; it does nothing about deletion, ransomware or a failed controller.

How the facts connect

A single task often touches several tables. Setting up a new file server means choosing a RAID level for its disks, opening the right ports in the firewall, creating users and setting permissions, and adding the server to backups. Questions follow the same chains, so practise explaining a whole task, not just isolated facts.

Be able to explain in a sentence

The difference between an incremental and a differential backup.
Why a domain login can fail when DNS is wrong.
What chmod 640 allows, and for whom.
Why RAID does not replace backups.
Which ports SSH, RDP, DNS and HTTPS use.
What a snapshot is useful for, and why it is not a backup.

Common questions

Which Linux commands matter most?

The everyday ones: navigating and listing files, viewing and searching text, managing users and permissions, checking disk and memory, controlling services and reading logs. Master those before the rarer tools.

Should I learn Windows commands too?

Yes. Know the common command-line and PowerShell tools for network settings, services and event logs, because many troubleshooting questions assume them.

More Systems Administrator guides

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Network Administrator key topics and quick reference