Re: How to make /etc/fstab "portable"?

[Dan LaBell <dan4l-nospam%verizon.net@localhost>]

On Feb 8, 2016, at 6:03 AM, Benny Siegert wrote:

> Hi!
>
> This may be a stupid question but: Is there a way to make the entry
> for the root filesystem in /etc/fstab just match whatever the kernel
> used as the root FS?
It doesn't look like it.  There is /kern/rootdev  and /kern/rrootdev  
which
provide a device file with the right major and minor numbers...  
BUT ... kern isn't mounted yet, and isn't available single user, So  
you CAN'T do this in fstab
/kern/rootdev /      ffs       rw                                   1 1

I think it would be great, if somehow one could have
/            /       ffs       rw                                   1 1
or maybe
a           /        ffs       rw                                   1 1
I was thinking if something like "stat -f %Sd" , could tell you root,  
then
really anything in C should be able to the same.  But, I'm then I  
realized,
there probably isn't a syscall to open a device just with major and  
minor.
I'm also guessing a program  can't mknod, open the the file, and then  
delete
the device file (like you could with a regular file), and even if you  
could
you couldn't unmount the filesystem...
But, then again if mount and fsck could stat /etc/fstab take st_dev ,  
and
then translate either a / or single letter in fstab , and produce the  
correct corresponding string for itself ,and any children it spawns  
you could have a
"portable" fstab, and /etc/rc.d/fsck could stay the same.  If the  
corresponding
device doesn't exist to be found, you'd be no worse off, than if that  
happened
presently, and no need for adhoc scripting.