System Administration Basics
Introduction
System administration is the field responsible for maintaining, configuring, and ensuring reliable operation of computer systems and servers. As a beginner in programming and computing, understanding the basics of system administration will give you valuable skills to manage your development environment and troubleshoot common issues.
This guide introduces fundamental system administration concepts that apply across most operating systems, with specific examples for both Linux and Windows environments. By the end of this guide, you'll have a solid understanding of the core responsibilities and tasks performed by system administrators.
What is System Administration?
System administration involves:
- Managing user accounts and permissions
- Monitoring system performance
- Installing and configuring software
- Managing system resources
- Ensuring system security
- Performing backups and recovery
- Troubleshooting system issues
Let's visualize the role of a system administrator:
User Management
One of the primary responsibilities of a system administrator is managing users and their permissions.
Adding and Removing Users
Linux
In Linux systems, you can add users with the useradd command:
# Add a new user
sudo useradd -m -s /bin/bash newuser
# Set password for the new user
sudo passwd newuser
To remove a user:
sudo userdel -r username
The -r flag removes the user's home directory and mail spool.
Windows
In Windows, you can manage users through the Command Prompt with administrator privileges:
# Add a new user
net user username password /add
# Add user to administrators group
net localgroup administrators username /add
# Remove a user
net user username /delete
Managing User Permissions
Linux
Linux uses a permissions system based on users, groups, and others:
# Change file ownership
sudo chown user:group filename
# Change file permissions
chmod 755 filename
Understanding permission numbers:
- 4: Read permission
- 2: Write permission
- 1: Execute permission
So 755 means:
- Owner: Read (4) + Write (2) + Execute (1) = 7
- Group: Read (4) + Execute (1) = 5
- Others: Read (4) + Execute (1) = 5
To check current permissions:
ls -l filename
Output example:
-rwxr-xr-x 1 user group 5432 Oct 15 14:30 filename
Windows
Windows uses Access Control Lists (ACLs) for permissions:
# View permissions
icacls filename
# Grant full control to a user
icacls filename /grant username:F
# Remove a user's permissions
icacls filename /remove username
Process Management
System administrators need to monitor and control running processes.
Viewing Running Processes
Linux
Use ps to view processes:
# View all processes
ps aux
# View process tree
ps axjf
Example output:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.3 169180 6872 ? Ss Oct15 0:09 /sbin/init
root 789 0.0 0.5 127224 10088 ? Ss Oct15 0:01 /usr/sbin/sshd
user 1234 0.2 1.0 157812 20416 pts/0 Ss 14:30 0:03 bash
Windows
Use Task Manager or the tasklist command:
tasklist
Example output:
Image Name PID Session Name Session# Mem Usage
========================= ====== ================ ======== ============
System Idle Process 0 Services 0 8 K
System 4 Services 0 5,192 K
Registry 96 Services 0 45,748 K
Managing Processes
Linux
# Kill a process
kill PID
# Force kill a process
kill -9 PID
# Find process by name
pgrep firefox
# Kill process by name
pkill firefox
Windows
# End a task by PID
taskkill /PID 1234
# Force end a task
taskkill /F /PID 1234
# End a task by name
taskkill /IM program.exe
Service Management
Services are programs that run in the background.
Managing Services in Linux
Modern Linux distributions use systemd:
# Start a service
sudo systemctl start apache2
# Stop a service
sudo systemctl stop apache2
# Enable a service (starts on boot)
sudo systemctl enable apache2
# Disable a service
sudo systemctl disable apache2
# Check service status
sudo systemctl status apache2
Example status output:
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2023-10-15 14:50:22 UTC; 2h 5min ago
Main PID: 1234 (apache2)
Tasks: 6 (limit: 4915)
Memory: 22.0M
CPU: 456ms
CGroup: /system.slice/apache2.service
├─1234 /usr/sbin/apache2 -k start
├─1235 /usr/sbin/apache2 -k start
└─1236 /usr/sbin/apache2 -k start
Managing Services in Windows
Windows uses the Service Control Manager:
# Start a service
net start service_name
# Stop a service
net stop service_name
# More detailed service management
sc query service_name
sc config service_name start= auto
sc config service_name start= disabled
File System Management
Disk Usage
Linux
# Check disk space
df -h
# Check directory size
du -sh /path/to/directory
Example output for df -h:
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 20G 12G 7.0G 63% /
/dev/sda2 100G 23G 77G 24% /home
Windows
# Check disk space
wmic logicaldisk get deviceid, size, freespace
# Alternative using PowerShell
Get-PSDrive -PSProvider FileSystem
File Search and Management
Linux
# Find files by name
find /path -name "filename"
# Find files by content
grep -r "search text" /path
# Find large files
find /path -type f -size +100M
Windows
# Find files by name
dir /s C:\path\filename*
# Find files by content
findstr /s /i "search text" C:\path\*.*
# PowerShell alternatives
Get-ChildItem -Path C:\ -Recurse -Filter "filename*"
Get-ChildItem -Path C:\ -Recurse | Select-String "search text"
System Monitoring
Checking System Resources
Linux
# Monitor system in real-time
top
# Memory information
free -h
# CPU information
lscpu
# Combined system stats
htop # may need installation
Example free -h output:
total used free shared buff/cache available
Mem: 15Gi 5.2Gi 2.8Gi 288Mi 7.5Gi 9.3Gi
Swap: 8.0Gi 0B 8.0Gi
Windows
# System information
systeminfo
# CPU utilization (PowerShell)
Get-Counter '\Processor(_Total)\% Processor Time'
# Memory usage (PowerShell)
Get-Counter '\Memory\Available MBytes'
Checking Logs
Linux
Most system logs are in /var/log:
# View system logs
less /var/log/syslog
# View authentication logs
less /var/log/auth.log
# Follow logs in real-time
tail -f /var/log/syslog
Windows
Windows stores logs in the Event Viewer:
# Open Event Viewer from command line
eventvwr
# View system logs with PowerShell
Get-EventLog -LogName System -Newest 10
# View application logs
Get-EventLog -LogName Application -Newest 10
Backup and Recovery
Creating Backups
Linux
# Backup a directory using tar
tar -czvf backup.tar.gz /path/to/directory
# Backup using rsync
rsync -av --delete /source/directory/ /backup/directory/
Windows
# Create a backup using robocopy
robocopy C:\source D:\backup /MIR
# PowerShell backup of a folder
Copy-Item -Path C:\source -Destination D:\backup -Recurse -Force
Scheduling Backups
Linux
Use crontab to schedule regular backups:
# Edit crontab
crontab -e
# Add a line to run a backup script daily at 2 AM
0 2 * * * /path/to/backup/script.sh
Windows
Use Task Scheduler or create a scheduled task from the command line:
schtasks /create /tn "Daily Backup" /tr "C:\scripts\backup.bat" /sc daily /st 02:00
Network Configuration
Checking Network Status
Linux
# Check IP configuration
ip addr show
# Test connectivity
ping -c 4 google.com
# Check open ports
ss -tuln
Example ip addr show output:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:15:5d:01:ca:05 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.100/24 brd 192.168.1.255 scope global dynamic eth0
valid_lft 86390sec preferred_lft 86390sec
Windows
# Check IP configuration
ipconfig /all
# Test connectivity
ping google.com
# Check open ports
netstat -an | findstr LISTENING
Configuring Network Interfaces
Linux
Edit the network configuration files or use the ip command:
# Set IP address temporarily
sudo ip addr add 192.168.1.100/24 dev eth0
# Set default gateway
sudo ip route add default via 192.168.1.1
For permanent changes, edit the appropriate configuration files based on your distribution.
Windows
# Set IP address
netsh interface ip set address "Ethernet" static 192.168.1.100 255.255.255.0 192.168.1.1
# Set DNS servers
netsh interface ip set dns "Ethernet" static 8.8.8.8
Basic Security Measures
Firewall Configuration
Linux (using ufw)
# Enable firewall
sudo ufw enable
# Allow SSH connections
sudo ufw allow ssh
# Allow web server
sudo ufw allow 80/tcp
# Check status
sudo ufw status
Example status output:
Status: active
To Action From
-- ------ ----
22/tcp ALLOW Anywhere
80/tcp ALLOW Anywhere
22/tcp (v6) ALLOW Anywhere (v6)
80/tcp (v6) ALLOW Anywhere (v6)
Windows Firewall
# Enable firewall
netsh advfirewall set allprofiles state on
# Allow an application
netsh advfirewall firewall add rule name="My Application" dir=in action=allow program="C:\path\to\app.exe"
# Allow a port
netsh advfirewall firewall add rule name="Allow Port 80" dir=in action=allow protocol=TCP localport=80
Checking for Security Updates
Linux
# Ubuntu/Debian
sudo apt update
sudo apt list --upgradable
sudo apt upgrade
# CentOS/RHEL
sudo yum check-update
sudo yum update
Windows
# Check for updates
wuauclt /detectnow
# Install updates (Windows 10/11)
Install-WindowsUpdate -AcceptAll
Automation with Scripts
System administrators often automate routine tasks using scripts.
Bash Script Example (Linux)
Here's a simple backup script:
#!/bin/bash
# Simple backup script
# Variables
SOURCE_DIR="/home/user/documents"
BACKUP_DIR="/mnt/backup"
DATE=$(date +%Y-%m-%d)
BACKUP_FILE="backup-$DATE.tar.gz"
# Create backup
echo "Starting backup of $SOURCE_DIR"
tar -czvf "$BACKUP_DIR/$BACKUP_FILE" "$SOURCE_DIR"
# Check if successful
if [ $? -eq 0 ]; then
echo "Backup completed successfully: $BACKUP_DIR/$BACKUP_FILE"
else
echo "Backup failed!"
fi
PowerShell Script Example (Windows)
# Simple backup script for Windows
$sourceDir = "C:\Users\user\Documents"
$backupDir = "D:\Backups"
$date = Get-Date -Format "yyyy-MM-dd"
$backupFile = "backup-$date.zip"
# Create backup directory if it doesn't exist
if (-not (Test-Path $backupDir)) {
New-Item -ItemType Directory -Path $backupDir
}
# Create backup
Write-Host "Starting backup of $sourceDir"
Compress-Archive -Path $sourceDir -DestinationPath "$backupDir\$backupFile" -Force
# Check if successful
if ($?) {
Write-Host "Backup completed successfully: $backupDir\$backupFile"
} else {
Write-Host "Backup failed!" -ForegroundColor Red
}
Summary
System administration is a broad field that encompasses many aspects of managing computer systems. In this guide, we covered the basics:
- User and permission management
- Process monitoring and control
- Service management
- File system operations
- System monitoring
- Backup and recovery
- Network configuration
- Basic security measures
- Automation with scripts
These skills form the foundation of system administration and will help you maintain your own systems, whether for personal use or in a professional environment.
Additional Resources
To further develop your system administration skills:
- Practice: Set up a virtual machine to practice these commands without affecting your main system.
- Documentation: Refer to official documentation for your operating system.
- Learn Shell Scripting: For Linux, learn more about Bash scripting; for Windows, learn PowerShell.
- Monitoring Tools: Explore more advanced tools like Nagios, Prometheus, or Grafana.
Exercises
- Create a new user on your system and assign them to a specific group.
- Write a script that checks system disk usage and sends an alert if it exceeds 80%.
- Set up a firewall rule to allow a specific application to access the network.
- Configure automatic backups of your important documents.
- Monitor your system's performance during high usage and identify potential bottlenecks.
If you spot any mistakes on this website, please let me know at [email protected]. I’d greatly appreciate your feedback! :)