01/03: doc: Clarify /dev/kvm setup.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit eca69fc0d69585b6c261c621599e5d7e10034306
Author: Ludovic Courtès <address@hidden>
Date:   Sun Jun 26 12:16:07 2016 +0200

    doc: Clarify /dev/kvm setup.
    
    Reported by myglc2 <address@hidden>.
    
    * doc/guix.texi (Build Environment Setup): Mention the "kvm" group.
    (Invoking guix system): Use "@quotation Note" for the note about KVM;
    make it clear that KVM is optional.
---
 doc/guix.texi |   19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index d6d16b4..9e3806c 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -708,8 +708,13 @@ Bash syntax and the @code{shadow} commands):
 @noindent
 The number of build users determines how many build jobs may run in
 parallel, as specified by the @option{--max-jobs} option
-(@pxref{Invoking guix-daemon, @option{--max-jobs}}).  The
address@hidden program may then be run as @code{root} with the
+(@pxref{Invoking guix-daemon, @option{--max-jobs}}).  To use
address@hidden system vm} and related commands, you may need to add the
+build users to the @code{kvm} group so they can access @file{/dev/kvm},
+using @code{-G guixbuild,kvm} instead of @code{-G guixbuild}
+(@pxref{Invoking guix system}).
+
+The @code{guix-daemon} program may then be run as @code{root} with the
 following address@hidden your machine uses the systemd init system,
 dropping the @address@hidden/lib/systemd/system/guix-daemon.service}
 file in @file{/etc/systemd/system} will ensure that
@@ -10224,12 +10229,14 @@ a list of available debugging commands.
 @end table
 @end table
 
-Note that all the actions above, except @code{build} and @code{init},
-rely on KVM support in the Linux-Libre kernel.  Specifically, the
-machine should have hardware virtualization support, the corresponding
address@hidden Note
+All the actions above, except @code{build} and @code{init},
+can use KVM support in the Linux-libre kernel.  Specifically, if the
+machine has hardware virtualization support, the corresponding
 KVM kernel module should be loaded, and the @file{/dev/kvm} device node
 must exist and be readable and writable by the user and by the
-build users of the daemon.
+build users of the daemon (@pxref{Build Environment Setup}).
address@hidden quotation
 
 Once you have built, configured, re-configured, and re-re-configured
 your GuixSD installation, you may find it useful to list the operating