Here are some Linux commands that everyone should be familiar with. In fact, you could argue that these are the first commands to memorise and build out your repertoire from there.
#BASIC LINUX COMMANDS #Clear the terminal window clear #Show kernel version uname -a #Show all tunable kernel parameters in the /proc/sys directory sudo /sbin/sysctl -a #Set a kernel parameter on the fly without persistence sudo /sbin/sysctl -w kernel.sysrq="1" #Set a kernel parameter with persistence /etc/sysctl.conf #Kernel parameters startup script /etc/rc.d/rc.sysinit #Show network interfaces ifconfig ip addr show #Configure network interface with persistence /etc/sysconfig/network /etc/sysconfig/network-scripts/ifcfg-eth0 #Show all filesystems and space df -ah #Show service status service udev status systemctl status udev #How much disk space is used by a given directory du ~/Downloads #What TCP and UDP ports is the listem listening on? netstat -tulpn sudo netstat -tulpn #gives more info on process name #Show information about a given process ps aux | grep containerd #Show free memory stats free #List block storage devices known to the system lsblk #Show mounted storage devices mount #Show filesystems that should be mounted at boot cat /etc/fstab #Mount everything in /etc/fstab mount -a #Mount a block storage device mount /dev/sdb1 /mnt #LVM Commands pvdisplay pvcreate pvremove pvchange vgdisplay vgcreate vgextend vgremove vgchange lvdisplay lvcreate lvextend lvremove lvchange mkfs.ext4 #Copy files cp rsync dd #Show command history history #Look up a command man -k <search-string> man grep