Master Linux Server Monitoring with watch, top, and ac Commands

Monitoring Linux Servers with watch

The watch command repeatedly executes a given command at a specified interval, allowing real‑time observation of changing values. By default it runs every 2 seconds; the -n option changes the period. $ watch -n 5 date Common uses include checking who is logged in and monitoring system load. For example, to see active users every 10 seconds: $ watch -n 10 who To watch the overall load average: $ watch uptime To count the total number of processes continuously: $ watch -n 5 'ps -ef | wc -l' To monitor memory usage in megabytes:

$ watch -n 5 free -m

Inspecting Processes with top

The top utility provides a dynamic, real‑time view of system metrics and per‑process resource consumption. By default it shows all users; the -u option limits the display to a specific user. $ top -u alvin The output includes CPU usage, memory usage, load averages, and a list of processes with their IDs, owners, and resource percentages.

Tracking Login Time with ac

The ac command (part of the acct or psacct package) reports accumulated login time for users. Running it without arguments shows the total time for all users. $ ac Adding -p displays per‑user totals, while -d breaks the data down by day.

$ ac -p

$ ac -d | tail -10

Conclusion

By combining watch, top, and ac, administrators can continuously observe server health, monitor individual user activity, and analyze resource consumption without leaving the command line.