Red Hat SummitChapter 35. Troubleshooting Xen
This chapter covers essential concepts to assist you in troubleshooting problems in Xen. Troubleshooting topics covered in this chapter include:
- troubleshooting tools for Linux and virtualization.
- troubleshooting techniques for identifying problems.
- The location of log files and explanations of the information in logs.
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 to develop your troubleshooting skills.
If you cannot find the answer in this document there may be an answer online from the virtualization community. See Section A.1, “Online resources” for a list of Linux virtualization websites.
35.1. Debugging and troubleshooting Xen
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:
Useful commands and applications for troubleshooting
-
xentop xentopdisplays real-time information about a host system and the guest domains.-
xm - Using the
dmesgandlog
vmstatiostatlsof
The
iostat, mpstat and sar commands are all provided by the sysstat package.
You can employ these Advanced Debugging Tools and logs to assist with troubleshooting:
XenOprofilesystemtapcrashsysrqsysrq tsysrq w
These networking tools can assist with troubleshooting virtualization networking problems:
ifconfigtcpdumpThetcpdumpcommand 'sniffs' network packets.tcpdumpis useful for finding network abnormalities and problems with network authentication. There is a graphical version oftcpdumpnamedwireshark.brctlbrctlis 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 ----------------------------------------------------------------------------- xenbr0 8000.feffffff no vif13.0 xenbr1 8000.ffffefff yes pddummy0 xenbr2 8000.ffffffef no vif0.0 # brctl showmacs xenbr0 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 xenbr0 xenbr0 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 on Red Hat Enterprise Linux 5. All utilities mentioned can be found in the
Server repositories Red Hat Enterprise Linux 5.
- 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 vncviewer using the
yum install vnccommand. - 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 vnc-servercommand.
