I am going to discuss some basic system monitoring commands here. Nothing big, most of the systems will have it pre-installed.
- top: Displays pid, user, CPU, physical memory and swap usage in real time. You can press M - to sort by memory, S - to sort by time, P - to sort by CPU interactively. You can also press u and k to check out user processes and kill one respectively.
- ps: It shows a list of processes. Use option -A for the entire list, -ef to get a detailed view and -u for user processes.
- vmstat: It provides statistics for processors, memory, swap, I/O and CPU.
- df: This is used to get information about the file system. It'll show you the size, used space, available space, used %, and mount information.
- du: It is used to check out the size of files. It goes recursively if you do not specify the file name.
- iostat: It provides the information about the Kernel version, average cpu usage and hardware devices. You might need to install sysstat package for this.
- who and w: Provides information regarding the number of people logged in. w provides more detailed report.