Linux with Operating System Concepts

PROBLEM 1: SYSTEM IS RUNNING INEFFECTIVELY
Description: Simple tasks are taking too long to execute. Log in is taking more time than 
expected. There is a delay between issuing a command and seeing its result.
Steps to determine the problem:
1. Use top, ps, the system monitor, and/or mpstat, sar, and pidstat to view the running 
processes.
a. Is CPU load heavy, approaching 100%?
b. Are there processes that are taking most of the CPU time or are there many pro-
cesses taking little time but combined that cause a heavy load?
2. Use vmstat and free to examine main memory and swap space utilization.
a. Is main memory full?
b. Is the system spending a lot of time swapping?
c. Are there too many processes in memory?
3. Use uptime to see how long the system has been running without a reboot. While 
Linux seldom needs to be rebooted, a reboot may resolve the problem.
Short-term solutions: Identify processes that can be halted and scheduled for later. 
Identify processes whose priorities can be lowered through renice, or those processes that 
could be moved to the background. Alternatively, can you contact the users and ask some 
of them to discontinue their processes and/or log off? Also, reboot the computer if the 
above steps do not solve the problem.
Long-term solutions: Purchase more main memory, increase the size of the swap parti-
tion (possibly add a second hard disk to contain more of the swap partition), and purchase 
a more powerful processor (or additional processors).
PROBLEM 2: SERVICE NOT RESPONDING
Description: Some service fails to respond such that users are receiving error messages 
when they attempt to use it. For instance, http requests to a web server result in server 
not found.
Steps to determine the problem:
1. Identify the service in question (from the users).
2. See if the service is running (e.g., /
sbin/service
 servicename 
status
).
3. See if the service’s supporting programs are running.

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Maintaining and Troubleshooting Linux
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4. View the configuration file for the service to see if it is configured correctly.
5. View the log file(s) generated as a response to the service.
Short-term solutions: Restart the service. Reconfigure the service. Restart supporting 
services. If needed, reboot the system.
Long-term solution: If the problem is related to a server (not service) that is not func-
tioning correctly, reinstall the server, or view the server’s web sites to see if there are solu-
tions to the given problem.