Installation guide
Chapter 34. Troubleshooting
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# 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 vnc command.
• 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-server command.
34.2. kvm_stat
The kvm_stat command is a python script which retrieves runtime statistics from the kvm kernel
module. The kvm_stat command can be used to diagnose guest behavior visible to kvm. In
particular, performance related issues with guests. Currently, the reported statistics are for the entire
system; the behavior of all running guests is reported.
The kvm_stat command requires that the kvm kernel module is loaded and debugfs is mounted.
If either of these features are not enabled, the command will output the required steps to enable
debugfs or the kvm module. For example:
# kvm_stat
Please mount debugfs ('mount -t debugfs debugfs /sys/kernel/debug')
and ensure the kvm modules are loaded
Mount debugfs if required:
# mount -t debugfs debugfs /sys/kernel/debug
kvm_stat output
The kvm_stat command outputs statistics for all virtualized guests and the host. The output is
updated until the command is terminated (using Ctrl+c or the q key).
# kvm_stat
kvm statistics
efer_reload 94 0
exits 4003074 31272
fpu_reload 1313881 10796