CPU, RAM and processes usage

The primary tool for checking CPU and RAM load is the :

top

More advanced and thus requiring more resources is:

htop

Linux process listing

We can list the processes running on the system:

ps -ef

Where:

• e - select all processes
• f - full format listing

Displayed columns:

• UID - user ID that owns the process
• PID - process ID
• PPID - parent process ID
• C - CPU usage percentage
• STIME - process start time
• TTY - associated terminal
• TIME - CPU time consumed
• CMD - command used to start the process

To limit the processes displayed, we can use this grep command to filter the returned results to keywords:

ps -ef|grep postgres

With bash command kill we can stop the selected process:

sudo kill 16900

Where:

• sudo - if we are not owner of process then we have to call command as super user
• 16900 - example PID (process ID)

If process is not responding we can call kill with -9 option, this will kill the process immediately:

sudo kill -9 16900

HDD/SSD storge

Checking free space on partitions:

df -h

Where:

• h - human readable format listing

Network interfaces

Show interfaces with IP addresses:

ip addr show

We can also install the older net-tools package:

sudo apt install net-tools -y

And use the command (similar to ipconfig from MS Windows):

ifconfig

To display existing network connections, we can use the command:

sudo netstat -tupan

Where:

• t - displays TCP connections
• u - displays UDP connections
• p - shows the process ID (PID) and program name of the process that owns each socket. Requires superuser privileges, so you might need sudo to use this option fully.
• a - displays all sockets, including: listening sockets, non-listening sockets
• n - displays numerical addresses and port numbers instead of resolving hostnames or service names