[Xen-users] Re: usage of the extra parameter in vm configs

[Bill Davidsen <davidsen@xxxxxxx>]

M.A. Williamson wrote:
> > On 30 Dec 2006 15:18:20 +0000, M.A. Williamson <maw48@xxxxxxxxx> wrote:
> > > We'd actually been talking about replacing the current "root=", "extra="
> > > etc. arguments with a single "cmdline=" which would contain the entire
> > > kernel commandline - in the same way that a normal bootloader might.
> > I think that's a good idea, because that was the next question I
> > wanted to ask: what's the difference between the root variable (which
> > in all examples not only contains the root, but alo the additional
> > argument "ro") and extra, and why should I not  just add more
> > arguments to the root variable and leave the extra arg empty?
> You could. Or you could stick them all in the "extra" argument. The only 
> real reason that the variables are done this way is that it decouples 
> the user from the realities of Linux a little... Additional variables 
> used to be used to pass IP / NFS root information on the command line 
> but I'm not sure if this is still done...
> The config file parser isn't *very* aware of how Linux command line 
> syntax works. At some stage it may be useful to make it more aware, for 
> purposes of providing more helpful configuration warnings - however, 
> this still doesn't really require the separate variables.
> Out of interest, would anybody on the users list object to a general 
> shift towards supplying the whole command line in one variable, rather 
> than piecemeal in specially named fields? We wouldn't have to break 
> backwards compatibility to do this...
I have to feel that the current setup is easier to read for infrequent 
users. And it makes support of new users easier, you can just tell them 
to set on value they can understand, and avoid 'where on the extras 
line?" questions.
And if you have to ask the value of one part of a command line, users 
can find the answer more easily if they're not familiar with the 
possibilities. It even makes comparing setups easier, tools like "diff" 
will isolate only what you have changed.
Being unambiguous reassures timid users.

--
bill davidsen <davidsen@xxxxxxx>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

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