Essential Linux Commands for Comprehensive System Inspection

1. System Information

uname -a

– display kernel version, operating system, and CPU architecture. head -n 1 /etc/issue – show the operating system version string. cat /proc/cpuinfo – list detailed CPU information. lspci -tv – enumerate all PCI devices in a tree view. lsusb -tv – enumerate all USB devices in a tree view. lsmod – list currently loaded kernel modules. env – display all environment variables for the current session.

2. Resource Usage

free -m

– show memory and swap usage in megabytes. df -h – display disk space usage for each mounted filesystem in human‑readable format. du -sh <directory> – report the total size of a specific directory. grep MemTotal /proc/meminfo – retrieve total physical memory. grep MemFree /proc/meminfo – retrieve free memory. uptime – show system uptime, number of users, and load averages. cat /proc/loadavg – display the three‑minute, five‑minute, and fifteen‑minute load averages. dmidecode | grep -i 'serial number' – obtain the motherboard serial number. cat /proc/cpuinfo or dmesg | grep -i 'cpu' or dmidecode -t processor – retrieve various CPU details. cat /proc/meminfo or free -m or vmstat – view comprehensive memory statistics. cat /proc/pci – list PCI card information. lspci | grep -i "VGA" or dmesg | grep -i "VGA" – check graphics (VGA) card details. dmesg | grep -i "eth", cat /etc/sysconfig/hwconf | grep -i eth, or lspci | grep -i "eth" – inspect network interface (Ethernet) information. cat /proc/bus/input/devices – view keyboard and mouse device data. cat /proc/bus/usb/devices – list USB device information.

3. Disk and Partition Details

mount | column -t

– display mounted partitions and their mount points. fdisk -l – list all disk partitions. swapon -s – show active swap partitions. hdparm -i /dev/hda – retrieve IDE disk parameters (only for IDE devices). dmesg | grep IDE – view kernel messages related to IDE device detection.

4. Network Information

ifconfig

– display properties of all network interfaces. iptables -L – list current firewall rules. route -n – show the routing table. netstat -lntp – list all listening TCP ports with associated processes. netstat -antp – list all established TCP connections with processes. netstat -s – display detailed network statistics.

5. Process Management

ps -ef

or ps -aux – list all running processes. top – provide a real‑time view of process resource usage.

6. User Information

w

– show currently logged‑in users and their activity. id <username> – display UID, GID, and group memberships for a specific user. last – view login history for all users. cut -d: -f1 /etc/passwd – list all system user accounts. cut -d: -f1 /etc/group – list all system groups. crontab -l – display the current user's scheduled cron jobs.

7. Service Management

chkconfig --list

– list all services and their run‑level settings. chkconfig --list | grep on – filter to show only services enabled to start.

8. Installed Packages

rpm -qa

– query and list every installed RPM package on the system.