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virt-dmesg lets you look at the kernel messages from most Linux guests on the host. It works even for hanging guests and so is a useful tool for debugging when things go wrong.

To test virt-dmesg, simply run it on the host with the name of a Linux guest (note: this tool does not work on non-Linux guests at all).

For example:

# virt-dmesg FedoraGuest | tail -10
<30>[   29.193332] fedora-storage-init[675]:               [  OK  ]
<30>[   29.382378] lvm[683]: 2 logical volume(s) in volume group "vg_f16x64" monitored
<30>[   29.567595] systemd-tmpfiles[685]: Successfully loaded SELinux database in 44ms 181us, size on heap is 468K.
<30>[   30.719712] livesys[694]: /etc/init.d/functions: line 58: /dev/stderr: No such device or address
<4>[   31.791292] multipathd (708): /proc/708/oom_adj is deprecated, please use /proc/708/oom_score_adj instead.
<6>[   34.362089] nf_conntrack version 0.5.0 (7873 buckets, 31492 max)
<6>[   34.546273] ip6_tables: (C) 2000-2006 Netfilter Core Team
<6>[   38.623282] 8021q: 802.1Q VLAN Support v1.8
<6>[   38.623380] 8021q: adding VLAN 0 to HW filter on device eth0
<7>[   47.994218] eth0: no IPv6 routers present

There are various other options and features available. Read the manual page:

$ man virt-dmesg