Linux/Unix:Generic

cp -rL

Copy recursively and dereference symbolic links (copy the file, not the link)

df -P

Report file-system information in parseble format.

df -h

Report file-system information in easy understandable precision (K, M or G when appropriate).

top

List process resource usage. By default having the most CPU-intensive process on top. Press > to have it sort on another column. Press 1 to have usage for each CPU apart.

lscpu

List CPU information

free

Show memory usage

cat /etc/sysctl.conf|grep swappiness

Check swappines (the eager the system will swap with). A higher number means more swapping will happen. 0 is not no swapping but minimal swapping.

uname -a

Show kernel version

mountpoint -q <directory>

Check if <directory> is in use as mountpoint

chage -l <username>

Show password aging status

RedHat (RHEL)

/etc/redhat-release

Redhat version installed

for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done

Find swapspace usage per process

Bash

:

No operation (NOP)

Raspberry pi autologon

In /etc/lightdm/lightdm.conf comment this line out (by putting a # in front of it)

lightdm.conf:autologin-user=pi