Some Linux guests may cause a high CPU load even if the guest system appears to be idle. This can be caused by a high timer frequency of the guest kernel. Some Linux distributions, for example Fedora, ship a Linux kernel configured for a timer frequency of 1000Hz. We recommend to recompile the guest kernel and to select a timer frequency of 100Hz.
Linux kernels shipped with Red Hat Enterprise Linux (RHEL) as of release 4.7 and 5.1 as well as kernels of related Linux distributions (for instance CentOS and Oracle Linux) support a kernel parameter divider=N. Hence, such kernels support a lower timer frequency without recompilation. We suggest to add the kernel parameter divider=10 to select a guest kernel timer frequency of 100Hz.
Most Linux-based guests will fail with AMD Phenoms or Barcelona-level Opterons due to a bug in the Linux kernel. Enable the I/O-APIC to work around the problem (see Section 3.5, “System settings”).
The following bugs in Linux kernels prevent them from executing correctly in VirtualBox, causing VM boot crashes:
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The Linux kernel version 2.6.18 (and some 2.6.17 versions) introduced a race condition that can cause boot crashes in VirtualBox. Please use a kernel version 2.6.19 or later.
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With hardware virtualization and the I/O APIC enabled, kernels before 2.6.24-rc6 may panic on boot with the following message:
Kernel panic - not syncing: IO-APIC + timer doesn't work! Boot with apic=debug and send a report. Then try booting with the 'noapic' option
If you see this message, either disable hardware virtualization or the I/O APIC (see Section 3.5, “System settings”), or upgrade the guest to a newer kernel.[51]
Guest desktop services in guests running the X11 window system
(Solaris, Linux and others) are provided by a guest service called
VBoxClient, which runs under the ID of
the user who started the desktop session and is automatically started
using the following command lines
VBoxClient --clipboard VBoxClient --display VBoxClient --seamless
when your X11 user session is started if you are using a common desktop environment (Gnome, KDE and others). If a particular desktop service is not working correctly, it is worth checking whether the process which should provide it is running.
The VBoxClient processes create
files in the user's home directory with names of the form
.vboxclient-*.pid when they are running
in order to prevent a given service from being started twice. It can
happen due to misconfiguration that these files are created owned by
root and not deleted when the services are stopped, which will prevent
them from being started in future sessions. If the services cannot be
started, you may wish to check whether these files still exist.
[51] See http://www.mail-archive.com/[email protected]/msg30813.html for details about the kernel fix.