[mythtv-users] SOLVED: Questions on PXE booting a frontend

[Jim Stichnoth]

A couple of clarifications:

On Thu, Aug 6, 2009 at 1:35 AM, Jim Stichnoth<stichnot at gmail.com> wrote:
> Other tips:
>
> o My files in the pxelinux.cfg directory look like this:
>     DEFAULT linux
>     LABEL linux
>     KERNEL vmlinuz-2.6.27.9-159.fc10.i686
>     APPEND ro root=192.168.0.205:/storage1/frontends/mythfe2/ROOT
> initrd=initrd-nfs-2.6.27.9-159.fc10.i686.img
> Notice the addition of initrd=... to the kernel arguments.  I have a
> separate file for each frontend because each NFS root path is different.
>
> o I noticed that mkinitrd and the associated nash program support a "dhcp"
> root file system type, which seems basically the same as "nfs" except that
> the root-path is taken from the DHCP server's response.  It would probably
> be better to add the root paths to /etc/dhcpd.conf, and then only have a
> single "default" file in the pxelinux.cfg directory.

I like the "--root=dhcp" root file system option to mkinitrd much
better.  However, I also have to add an option to explicitly include
the network hardware module, which for my IONITX is
"--with=forcedeth".  Then there is just one file, "default", in the
pxelinux.cfg directory:
    DEFAULT linux
    LABEL linux
    KERNEL vmlinuz-2.6.27.9-159.fc10.i686
    APPEND ro initrd=initrd-nfs-2.6.27.9-159.fc10.i686.img
And the root path gets moved to /etc/dhcpd.conf:
    allow booting;
    allow bootp;
    option subnet-mask 255.255.255.0;
    option broadcast-address 192.168.0.255;
    option domain-name-servers 192.168.0.1;
    option routers 192.168.0.1;
    subnet 192.168.0.0 netmask 255.255.255.0 { }
    group {
            next-server 192.168.0.205;
            filename "pxelinux.0";
            host mythfe1 {
                hardware ethernet xx:xx:xx:xx:xx:xx;
                fixed-address 192.168.0.206;
                option root-path
"192.168.0.205:/storage1/frontends/mythfe1/ROOT";
            }
            host mythfe2 {
                hardware ethernet yy:yy:yy:yy:yy:yy
                fixed-address 192.168.0.207;
                option root-path
"192.168.0.205:/storage1/frontends/mythfe2/ROOT";
            }
    }

> o The frontend now idles at 18 watts according to the Kill-a-Watt device.
> I'm thinking of replacing the 2 1GB SDRAM modules with a single 2GB module,
> which would leave more open space for passive cooling, and perhaps even drop
> the power usage by a watt...

It occurred to me to test this by pulling one of the SDRAM modules.
With 1 GB of memory, the system idles at 15-16 watts!  Video playback
was still completely smooth, except that I had some troubles with OSD
Fade on 720p and higher, so I disabled fading.  (In the JYA VDPAU 0.21
backport code I'm running, it's well-known that the OSD code is
inefficient since it doesn't yet use VDPAU.)  So far everything is
running within the 1GB, and there is no swap space defined.

Also, to answer one of the questions in my original post.  I did some
mild NFS torture testing to see what would happen to the frontend,
with its NFS-mounted root file system, when the NFS server goes down
and up.  I tried stopping and starting the NFS service, as well as
rebooting the NFS server.  In both cases, commands executed on the
frontend tended to freeze, but they would resume within a few seconds
of the NFS service coming back.  No kernel panics or permanent freezes
or anything.  I don't know if my NFS setup has any special
configuration (for example, I'm using automount for the non-root NFS
file systems), but I'm very happy with the result.

Jim