Command
Description
"uname -a" or "lscpu"
Display CPU architecture
which <command>
Gives path to command binary
watch [ -n (interval in seconds), -b (beep on non-zero exit) ] <command>
Execute a command periodically
df
Display mounted disks usage
lsusb
Display info about USB buses and devices connected to them
More at https://www.geeksforgeeks.org/linux-unix/linux-commands-cheat-sheet/
Environment Variable
Description
$SHELL
Current shell
$XDG_SESSION_TYPE
Display communications protocol
$EDITOR
Preffered text editor
$PATH
Where system looks for commands
SSH File/Folder Permissions
Item
Sample
Numeric
Bitwise
SSH folder
~/.ssh
700
drwx------
Public key
~/.ssh/id_rsa.pub
644
-rw-r--r--
Private key
~/.ssh/id_rsa
600
-rw-------
Authorized Keys
~/.ssh/authorized_keys
600
-rw-------
Config
~/.ssh/config
600
-rw-------
Home folder
~
755
at most drwxr-xr-x at most
Item
Sample
Numeric
Bitwise
U2f keys
/etc/u2f_users (/etc/Yubico/u2f_keys)
644
-rw-r--r--
More at https://marcusb.org/posts/2024/03/consolidated-guide-to-using-yubikeys-with-linux/