Editing Kernel configuration

This article summarises various kernel configuration issues.

== OpenVZ related kernel config options ==

Please make sure the following config options are enabled
in your kernel .config file before compilation process:
 CONFIG_SCHED_VCPU=y
 CONFIG_FAIRSCHED=y

 CONFIG_SIM_FS=m
 CONFIG_VZ_QUOTA=m
 # CONFIG_VZ_QUOTA_UNLOAD is not set
 CONFIG_VZ_QUOTA_UGID=y

 CONFIG_VE=y
 CONFIG_VE_CALLS=m
 CONFIG_VZ_GENCALLS=y
 CONFIG_VE_NETDEV=m
 CONFIG_VE_ETHDEV=m
 CONFIG_VZ_DEV=m
 CONFIG_VE_IPTABLES=y
 CONFIG_VZ_WDOG=m

 CONFIG_VZ_CHECKPOINT=m

{{Note|On architectures that do not currently support checkpointing (i.e. ppc and sparc) <code>CONFIG_VZ_CHECKPOINT</code> should be set to <code>n</code>}}

== ACPI sleep ==

It is a bit tricky to make ACPI sleep and OpenVZ work together.

ACPI sleep is enabled by <code>ACPI_SLEEP</code> kernel option. The following dependencies are declared in kernel configs:

 ACPI_SLEEP depends on X86 && (!SMP || SUSPEND_SMP)
 SUSPEND_SMP depends on HOTPLUG_CPU && X86 && PM
 FAIRSCHED depends on SCHED_VCPU

And <code>SCHED_VCPU</code> is incompatible with <code>HOTPLUG_CPU</code>:

 ./kernel/cpu.c:#error "CONFIG_HOTPLUG_CPU isn't supported with CONFIG_SCHED_VCPU"

On non-SMP machine, you may disable <code>SMP</code>, this will resolve the conflict.

If you have SMP machine, you can only disable <code>FAIRSCHED</code> and <code>SCHED_VCPU</code>. It will reduce some isolation between VEs (CPU scheduling will be performed per-task, not per-VE, and <code>cpuunits</code> and <code>cpulimit</code> settings will not take effect), but it is an acceptable solution if your VEs are trusted (and it's hard to imagine untrusted VEs on a notebook.)

[[Category:Kernel]]
[[Category:HOWTO]]