On Wed, 2009-06-10 at 09:41 +0200, Seewer Philippe wrote:
> David Dillow wrote:
> > On Tue, 2009-06-09 at 17:35 +0200, Seewer Philippe wrote:
> >> NFS
> >> ---
> >>
> >> Preferred format:
> >> root=nfs[4]:[server:]path[:options]
> >>
> >> Legacy formats:
> >> root=/dev/nfs[4] nfsroot=[server:]path[,options]
> >>
> >> If server is unspecified it will be pulled from one of the following
> >> sources, in order:
> >> static ip= option on kernel command line
> >> DHCP next-server option
> >> DHCP server-id option
> >>
> >> Other formats:
> >> root=nfs[4]
> >> Plain "root=nfs" interprets DHCP root-path option as
> >> [ip:]path[:options]
> >>
> >> ==> Question: I've never used/seen root=nfs before. If server-ip is
> >> missing in root-path should dhcp next-server/server-id be used?
> >
> > root=nfs is something I did early on as a shortcut for root=/dev/nfs
> > which is supported by the kernel's nfsroot code. Similarly,
> > root={/dev/,}nfs4 is an invention to handle newer NFS versions.
> >
> > If server-ip is missing, then it should be filled in via the server
> > argument from the appropriate ip= line, or via dhcpd
> > next-server/server-id.
>
> Hmmm... so you say root=nfs is just a short version of root=/dev/nfs? In
> that case the documentation isn't up to date, since (see above) root=nfs
> says specifically that it uses dhcp root-path.
root=nfs works exactly as root=/dev/nfs works exactly as nfsroot=... it
will use DHCP root-path, and override it with the parts it can get from
the command line.
> If this is really a dracut specific "invention" I suggest we drop this.
I'd prefer to keep root=nfs as a shorthand if we keep root=/dev/nfs.
Same for root=nfs4 and root=nfs4.
But this is probably about as hard as I will argue to keep them; they
fall out easily from the legacy support.
> >> NBD
> >> ---
> >>
> >> Preferred format:
> >> root=nbd:srv:port[:fstype[:rootflags[:nbdopts]]]
> >>
> >> nbdopts is a comma seperated list of options to give to nbd-client
> >>
> >> Legacy formats:
> >> nbdroot=srv,port
> >>
> >> ==> Question: What should root= contain here? Is having no or an empty
> >> root= ok?
> >
> > Legacy would be root=/dev/ndb[0-9]+ but Warren has suggested we drop
> > that. With my netroot= patches -- coming soon to a list near you! ;) --
> > the NBD handler will default to /dev/nbd0, or will be able to specify
> > root=LABEL=/ or root=/dev/lvm-volume/lv-name etc to use the same
> > features we get when root is on a local disk.
>
> Hmmm... OK. The point here is that, if say nbdroot= (or iscsiroot=,
> nfsroot=) is available, we should just ignore root= completely?
Perhaps at current, but not in the very near future -- I'm adding
support for doing proper root on LVM/LUKS when using NBD, so that will
need a root=, but it will default to root=/dev/nbd0 if it is not
present.
> >> ==> Question 2: The RFC specifically says hostnames or ipv6 addresses
> >> are allowed for servername. Do we have to support this?
> >
> > I think we should, yes. IPv6 support is something we're going to want in
> > general, but it will present some challenges to our parsing schemes.
> >
> > Perhaps we would put some limits on using IPv6 in the legacy options (no
> > ip= static config for IPv6, require the full nfs:IP:server[:,]opts
> > format, etc.)
>
> Indeed it does. And to think further, there are two ipv6 autoconf
> possibilities: stateless (router adviced) or stateful (dhcp6).
>
> Legacy options should be ok, since they only contain "addresses". I'd
> suggest to add a ip6= option for full ipv6 support later on.
Parsing nfsroot=fe80::2e0:29ff:fe34:de52:/diskless:hard,nointr is going
to be fun. :)
> As for DNS: If we use DHCP, you're correct. It's almost free. But we
> don't have any ip= options for static configuration to set the DNS
> Server...
Use DHCP if you want DNS support? Or do host specific and we can
use /etc/resolv.conf.
DHCP can also point us to the right LDAP server etc, but I'm not sure
that's worth the effort. Which I guess is to say I don't care enough to
implement but I wouldn't stop someone else if they did it in a clean
manner and it didn't bloat my initrd if I didn't use it.
Thanks for working on the user experience; I think that will be good for
dracut.
Dave
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