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What tool do you use to monitor your servers?
In Windows I use the Performance Monitor to see how much CPU, memory etc my server is using. Is there something similar to see percentage of memory use, percentage of CPU use etc for Linux? (other than vmstat) What is the best for real time analytics for Linux?
How about
top
?vmstat, iostat, htop, ntop, mmmbop, plain top, certain "files" read from /proc...
There's a number of utilities that can be set by threshold to notify you of trouble. It depends on what you're looking to monitor exactly. Windows actually came out ahead in monitoring real-time minutiae between the sysinternals suite and perfmon, in my opinion.
Also be aware that the monitoring tools can be deceiving. The counters may not be 100% accurate to what you're looking for. This really depends on what exactly you're trying to do (general monitoring, alarms, troubleshoot something...?)
I would suggest htop. Curses based good looking and efficient app does better than top.
IO data - iostat memory data - vmstat CPU data - mpstat overall system view - top process information - ps aux or ps -xv system information on a broad range of time - sar (sysstat package in RHEL, Fedora, CentOS) network data - netstat Open file idata - lsof, fuser
Certain files in /proc are also informative but requires some experience. In fact, all of these tools except sar read from some /proc files.
More detailed data -perf in RHEL6, oprofile in RHEL5.
Give me a shout if you need names of the files in /proc you should know of.