Questions and answers

1. Capacity Planning


What tools can be used to show block device Input/Output statistics?

iostat, vmstat, and sar are some of the tools that can be used to output block device I/O.

The iostat command The vmstat command The sar command


What does the first column of the output of vmstat, called 'r' represent?

The number of processes currently allocated to the processor run queue.

processor run queue


Which kernel module has to be loaded on post-2.4 kernels in order for /proc/net/ip_conntrack to exist?

Only if the ipt_MASQUERADE kernel module is loaded will /proc/net/ip_conntrack exist.

IP Masquerading


What is the main difference between netstat -r and route -e since their output is identical?

The route -e requires elevated privileges whereas netstat -r can be run with user privileges.

netstat --route or -r option


What are the three different kind of options which can be passed to the GNU ps command?

GNU long options, UNIX and BSD.

The ps command


What command can be used to display processes formatted as a tree?


The pstree command


What command can be used to list all open files and their corresponding processes?

The lsof will list all open files and their corresponding processes.

The lsof command


Resource related problems are the result of what?

Resource related problems are the result of one or more resources not being able to cope with the demand during certain circumstances.

Resource Exhaustion


Problems reported by users are often related to availability or resources, and the performance of their application in particular. What needs to be determined first in order to be able to determine whether these lack of performance based claims are indeed valid or not?

A baseline needs to be determined on a system which behaves properly. This baseline can then be used as a reference for identical or similar systems.

Create a baseline


What needs to be created first when investigating a possible network related bottleneck?

A map of the network should be created before troubleshooting network issues.

Identifying network bottlenecks


What command can be used to show both the amount of physical and virtual memory, and how much memory is being used?

Several utilities like top and htop can be used, but the free command will show detailed information about the allocation of the memory in use. (htop is an interactive process viewer from the Debian htop package)

The free command

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