Red Hat Enterprise Linux 5 Administration Unleashed

Monitoring and Tuning Troubleshooting 557Q. Why does the syslog only report recent data?A. If the syslog were allowed to grow indefinitely, it would eventually fill up the partitionthat it resides on. The logrotate daemon allows the syslog to be flushed out at aspecified interval. By default, the logrotate daemon will keep up to four weeks ofprevious system logs. Once every week, the current /var/log/messages file will berenamed to /var/log/messages.1 and a new /var/log/messages file will be created.If you need to keep syslogs for more than four weeks, this can be configured in the/etc/logrotate.conf file.Q. Why is my system running slow?A. Poor system performance can be caused by a number of factors. More often thannot, performance problems are caused by excessive demand of the CPU, systemmemory, or the I/O subsystem.Start troubleshooting by using the sysstat utilities as discussed in Chapter 20,“Monitoring System Resources” to determine if any of your resources are being100% utilized for prolonged periods of time. Also consider writing scripts and schedulingthem with cron so you can collect this data on a consistent basis as discussedin “Automating Tasks with Scripts,” also in Chapter 20.Q. Several times on my network file server a user has used all the free disk space in the/home partition, causing all users to receive failure to write to disc errors. How can Imonitor the disk space on the partition and limit users to a specific amount of diskspace?A. Monitoring the amount of disk space free can be done easily with the audit daemon asdiscussed in Chapter 25, “Linux Auditing System.” To limit the amount of disk space auser is allowed, try using disk quotas is discussed in Chapter 7, “Managing Storage.”Q. I suspect that the I/O transfer rates for my system are slower than they are supposedto be. How can I determine what the actual transfer rates are for my hard drives?A. Try using iostat as discussed in Chapter 20 to monitor the transfer rates over aperiod of time. After gathering this information for a few weeks or even a month,calculate the averages to determine if your hard drives are performing adequately.Remember this task can be automated with cron as discussed in Chapter 11,“Automating Tasks with Scripts.”Q. I am seeing the message kernel: CPU0: Temperature above threshold, cpu clockthrottled displayed at the console and virtual terminals. What is causing this andhow can I prevent it?DA. This message is displayed when the processor has reached its maximum safe temperature.If the processor goes above this threshold, it might harm the processor. If yousee this warning, check the processor fan to make sure it is running and seatedproperly. If it is not running or there is physical damage, replace the processor fan.If the fan seems to be working properly, check the BIOS of your system for processorfan settings to make sure it is allowed to run at full capacity should it need to. Ifyou still see the message, try replacing the processor with a known good processoror take the processor somewhere to be tested.