Re: Root device independent bootable disk images

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello.  Perhaps I don't understand what this change means, exactly,
but if this change goes forward, will one still be able to specify a
specific device as the root disk even if it is not the boot disk?  For
example, specifying a raid5 set as the root when booting from a single
disk, or, setting a hard disk as the root when booting from flash media?

-thanks
-Brian
On Dec 13,  5:51pm, Christos Zoulas wrote:
} Subject: Re: Root device independent bootable disk images
} In article <23569.9846.9159.416183%guava.gson.org@localhost>,
} Andreas Gustafsson  <gson%gson.org@localhost> wrote:
} >Hi all,
} >
} >Since jmcneill's commit of src/lib/libutil/getfsspecname.c 1.5, NetBSD
} >supports the special string "ROOT." as an alias for the root device in
} >/etc/fstab.  This can be used to avoid hard-coding the device name of
} >the root disk on bootable disk images, allowing a single image to be
} >booted from disks having different device names.
} >
} >This feature is currently used by the ARM images, but not by the
} >images for other architectures.  I would like to change this.  My
} >immediate motivation for this is to fix PR 51503, "7.0.1/amd64 USB
} >install image root mount fails when sd present", but I belive it would
} >also be useful on live images as well as install images, and on
} >other architectures.  Note that I am not proposing changing the fstab
} >that gets written to the target disk when installing a system using
} >sysinst, only that of pre-built disk images such as those from
} >"build.sh install-image" or "build.sh live-image".
} >
} >The question is, is there any reason to keep the existing machinery
} >for specifying a fixed device name via the BOOTDISK make variable?
} >Or in other words, can anyone think of an architecture or type of disk
} >image where the "ROOT." reference might not work, or where a
} >hard-coded root disk device in /etc/fstab might otherwise be
} >desirable?
} >
} >If not, the change I'm proposing would basically amount to changing
} >"/dev/@@BOOTDISK@@" to "ROOT." in src/distrib/common/bootimage/fstab.in
} >and fstab.install.in, followed by a bunch of cleanup work to remove
} >things that are no longer used or needed, such as all references to
} >BOOTDISK in the Makefiles.
} >
} >The "build.sh live-image" target currently builds two live images each
} >for i386 and amd64, with names containing "-wd0root" and "-sd0root",
} >respectively.  With the proposed change, these would become almost
} >identical, differing only in size and the OMIT_SWAPIMG setting, and
} >probably ought to be merged into one.  Other architectures only have
} >at most a single live image each, but their names also contain strings
} >like "-sd0root" or "-ra0root" that would now be meaningless and should
} >be removed.
} >
} >Comments?  Objections?
} 
} I think this is a good idea!
} 
} christos
} 
>-- End of excerpt from Christos Zoulas