Quick Reference of common used commands

Identify CPU/Hardware

dmidecode | less (shows everything in BIOS)

cat /proc/cpuinfo

less /proc/cpuinfo

lscpu (lists available cpus)

lshal (list all hardware visible by HAL)

lspci (shows all PCI devices)

lsusb (shows all USB devices)

lsblk (shows all block devices like hardrives, cdroms)

lsmod (shows installed device drivers/modules)

df -h (disk space usage)

du -h (estimate disk usage)

cat /proc/partitions (show partitions)

hdparm -i /dev/sda

hwinfo

hwinfo --short

hwinfo | more

grep processor /proc/cpuinfo | wc -l (If the load averages show that the load is increasing and is above the number of CPUs, you should look at what is causing the load. Load is a combined measure of CPU and I/O utilisation so top can be used to get real-time statistics.)

vmstat 5 10 (the free column shows that the amount of free memory, The si and so columns show the amount of data being transferred between the systems swap and its memory)

 

Network

ifconfig -a

ifconfig -a|less

more  /etc/sysconfig/network-scripts/ifcfg-eth0

route -n

route (shows network route)

netstat -tulpn (list of all open ports)

 

 

Identify Memory

cat /proc/meminfo

free

free -m (shows memory and swap information)

free -mt

free -gt

 

Identify Kernel (Linux version)

cat /proc/version

uname -mrs

uname -a

lsb_release -a

cat /etc/*release*

top (display list of tasks)

ps aux (display all running processes)

ps aux | grep process-name

rpm -qa (shows what software is installed)

rpm -qa | grep 'software-name'

rpm -qa | less

 

User

ulimit -a (find out user limits)

ps -p $$ | tail -1 | awk '{ print $4 }'  (find out user shell)

tail -f /var/log/secure (view login logs)

vi /var/log/secure (view login logs)

grep 'something' /var/log/secure (view login logs)

who (whos logged on)

groups userid (shows what groups a user is a member of) note: could also do $ grep userid /etc/group

lid -g groupname (shows members of a group) note: could also do $ grep '^groupname' /etc/group