Overview

Good system administration starts with knowing what your system is doing. These tools help you monitor performance, manage processes, handle backups, and keep your packages up to date.

Process & Performance Monitoring

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top
Real-time view of running processes and system resource usage. Press q to quit, k to kill a process.
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ps
Snapshot of current processes. ps aux shows everything. Pipe to grep: ps aux | grep apache.
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df / du
df -h shows disk usage per filesystem. du -sh /var/log shows size of a directory.
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free
free -m shows RAM and swap usage in megabytes. Essential for diagnosing memory pressure.

Package Management

# Debian / Corel / Mandrake (apt):
# apt-get update            # refresh package lists
# apt-get install package   # install a package
# apt-get upgrade           # upgrade all packages

# Red Hat / Caldera / SuSE (rpm):
# rpm -ivh package.rpm      # install
# rpm -Uvh package.rpm      # upgrade
# rpm -qa                   # list all installed packages
# rpm -e packagename        # remove

Backup Tools

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tar
The standard Unix archiving tool. tar czf backup.tar.gz /home/user creates a compressed archive. tar xzf backup.tar.gz extracts it.
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rsync
Efficient file synchronisation tool. Only transfers changed bytes. rsync -avz /home/ backup@server:/backups/.