Here are a number of example commands to check various points of a Linux system, disk, swap, memory, CPU, network and other system information. This covers basic hardware and core system commands. This is considered fundamental knowledge for any Linux System Administrator

CPU Information

This is all contained in /proc/cpuinfo which can be viewed with

cat /proc/cpuinfo

Check Number of Cores

egrep '^processor' /proc/cpuinfo

Check Processor for 64bit

grep ' lm ' /proc/cpuinfo

Check for Virtualization

egrep '^flags.*(vmx|svm)' /proc/cpuinfo

Memory Information

Kernel Memory Details

cat /proc/meminfo

System Memory Details

free -m

Swap Information

cat /proc/swaps

Also /etc/fstab

Disk Information

Disks List

Use one of the following

ls /sys/block
ld /dev/sd*
dmesg |grep disk

Mounted Disk Space / Size

Most commonly using df -h.

df -h
Filesystem       Size  Used Avail Use% Mounted on
rootfs           145G  109G   29G  79% /
/dev/root        145G  109G   29G  79% /
devtmpfs         2.0G  240K  2.0G   1% /dev
rc-svcdir        1.0M   92K  932K   9% /lib64/rc/init.d
shm              2.0G  3.7M  2.0G   1% /dev/shm
tmpfs            2.0G     0  2.0G   0% /lib64/firmware
c:raid           917G  725G  146G  84% /mnt/raid

Kernel Information

uname -a
find /boot/
cat /boot/syslinux.cfg
cat /boot/grub/menu.lst
lsmod

Network Information

Devices have names like eth0, wlan0, ath0, br0

ifconfig
route
traceroute
ping
dig
host
brctl
tunctl
netstat -tanpu
cat /etc/resolv.conf
cat /etc/conf.d/net
cat /etc/conf.d/hostname
cat /etc/hostname
cat /etc/network/*