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Chapter 21. Troubleshooting
This chapter covers common problems and solutions for Red Hat Enterprise Linux 6 virtualization issues.
Read this chapter to develop an understanding of some of the common problems associated with virtualization technologies. 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 B.1, “Online Resources” for a list of Linux virtualization websites.
21.1. 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:
These networking tools can assist with troubleshooting virtualization networking problems:
tcpdumpcommand 'sniffs' network packets.
tcpdumpis useful for finding network abnormalities and problems with network authentication. There is a graphical version of
brctlis a networking tool that inspects and configures the Ethernet bridge configuration in the 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 # brctl showmacs virtbr0 port-no mac-addr local? aging timer 1 fe:ff:ff:ff:ff: yes 0.00 2 fe:ff:ff:fe:ff: yes 0.00 # brctl showstp virtbr0 virtbr0 bridge-id 8000.fefffffffff designated-root 8000.fefffffffff root-port 0 path-cost 0 max-age 20.00 bridge-max-age 20.00 hello-time 2.00 bridge-hello-time 2.00 forward-delay 0.00 bridge-forward-delay 0.00 aging-time 300.01 hello-timer 1.43 tcn-timer 0.00 topology-change-timer 0.00 gc-timer 0.02
Listed below are some other useful commands for troubleshooting virtualization.
- strace is a command which traces system calls and events received and used by another process.
- vncviewer: connect to a VNC server running on your server or a virtual machine. Install vncviwer using the
yum install tigervnccommand.
- vncserver: start a remote desktop on your server. Gives you the ability to run graphical user interfaces such as virt-manager via a remote session. Install vncserver using the
yum install tigervnc-servercommand.