How to check if a server is up and running or down in Linux?

How to check if a server is up and running is quite difficult task, yet Linux servers are often preferred over other OS to meet the rapid, varying demands of a business as it is a free and open source operating system. It offers an enhanced flexibility and stability along with increased permissions. A Linux server performs at its best when running at run level 3. Here the network, as well as multiple users, are thoroughly supported, but will not start GUI when the machine boots. So what is happening with a Linux server, you can check if a server is up and running with the following monitoring commands.

How to check if a server is up and running?

If the server starts with booting into a graphical desktop, change it by using the editor on /etc/inittab. Then figure out the intdefault line and change it to:

id:3:initdefault:

If the inittab file is absent, create it and name it id:3, save and exit in order to boot into the third run level when you boot into the server, next time. Make use of the init3 command to rapidly set the server’s run level if you do not prefer to reboot after this change. If the server starts to run at init3, the following shell programs can be used to monitor what is happening inside.

1. iostat: Monitor the storage subsystem functioning like the disk utilization, Read/Write rate, etc.

2. meminfo: Memory information

3. free: Memory overview

4. mpstat: CPU activity

5. netstat: A variety of network-related information

6. nmon: Performance information (subsystems)

7. pmap: Amount of memory used by the server processors

8. ps, pstree: enlists the currently running processes

9. sar (system activity reporter): CPU utilization, storage device activity, etc.

10. s trace: diagnosing tool

11. tcpdump: network overview

12. top: monitors the active processes including CPU load, memory utilization, etc.

13. uptime: the time duration the server has been running and how many users are currently using it.

14. vmstat: monitor virtual memory like swap memory utilization report

15. dmesg: monitors and displays all the server errors.

Some other useful commands to get some information regarding the server are:

runlevel – Information about the Present Run Level
netstat –a – View the Network sessions
netstat –rn – To see the gateways configured
who/finger – Users logged in detail
ps –ef – To have a look on the complete set of running process and the related files
sestatus – Verify SELINUX status
service iptables status – To check firewall status
ifconfig –a – To see the Network cards and configured IP Address

PING

A ping command can be used in Linux to check if a server is up through the connection between two networks, whether in a LAN or WAN or on the internet, altogether.

Type “ping” in the command window after opening the terminal window
Keep a space and then type the required IP address to ping
Now press Enter and receive the replies if the site is up
Finally, Press Ctrl C to show the results after stopping the command

Carefully using all these commands, we can have a better check if a server is up and running by understanding the present status of Linux servers.