Installation guide

Chapter 34.
303
Troubleshooting
This chapter covers common problems and solutions for Red Hat Enterprise Linux 6 virtualization
issues.
This chapter is to give you, the reader, a background to identify where problems with virtualization
technologies are. Troubleshooting takes practice and experience which are difficult to learn from a
book. It is recommended that you experiment and test virtualization on Red Hat Enterprise Linux 6 to
develop your troubleshooting skills.
If you cannot find the answer in this document there may be an answer online from the virtualization
community. Refer to Section A.1, “Online resources” for a list of Linux virtualization websites.
34.1. Debugging and troubleshooting tools
This section summarizes the System Administrator applications, the networking utilities, and
debugging tools. You can employ these standard System administration tools and logs to assist with
troubleshooting:
• kvm_stat
• kvmtrace
• vmstat
• iostat
• lsof
• systemtap
• crash
• sysrq
• sysrq t
• sysrq w
These networking tools can assist with troubleshooting virtualization networking problems:
• ifconfig
• tcpdump
The tcpdump command 'sniffs' network packets. tcpdump is useful for finding network
abnormalities and problems with network authentication. There is a graphical version of tcpdump
named wireshark.
• brctl
brctl is a networking tool that inspects and configures the Ethernet bridge configuration in the
Virtualization linux kernel. You must have root access before performing these example commands:
# brctl show
bridge-name bridge-id STP enabled interfaces
-----------------------------------------------------------------------------
virtbr0 8000.feffffff yes eth0