Gathering information and monitoring an Ubuntu system from a terminal

Though this information applies to any GNU/Linux kernel I thought it would be helpful to describe some ways in which to uncover information about a system through a terminal. This is especially useful when running Ubuntu Server without any graphical desktop environment but can also be useful for desktop users. Mostly I’ll just reveal some useful locations to find information in the /proc and /dev directories.

System information

• cat /proc/cpuinfo
  Lists each CPU core and its model, current speed, l2 cache size, and a number of flags describing the capabilities of the cpu and supported instructions.
• cat /proc/meminfo
  Lists lots of details about memory and swap status. Can be monitored with the command watch cat /proc/meminfo.
• cat /proc/interrupts
  Useful in diagnosing some problems and also in checking to see if NMI is enabled and functioning.
• cat /proc/loadavg
  Mostly the same information shown in top but useful for scripting based on load.

Disk information

• cat /proc/mdstat
If running GNU/Linux software RAID this will show the state of the RAID arrays and progress report in a resynchronization. The command watch cat /proc/mdstat can be useful in monitoring a resynchronization.
• cat /proc/diskstats
  Not easy to use because I, and I suspect most people, will have to look up what each field means. But these can be very useful in understanding the disk workload of a server.
• cat /proc/partitions
  Shows the layout of all disks. This can be very helpful if one does not know the layout of a system.
• cat /proc/swaps
  This will display the active swap files and partitions on the system.
• ls -l /dev/disk/by-uuid
  This shows the UUID’s of all partitions and which partition they map to.
• ls /dev/mapper
  Lists the current device mapper devices.