svn commit: r320803 - head/sbin/mount

[Ian Lepore]

On Sat, 2017-07-08 at 10:15 -0700, Rodney W. Grimes wrote:
> [ Charset ISO-8859-1 unsupported, converting... ]
> > 
> > On Sat, 2017-07-08 at 09:50 -0700, Rodney W. Grimes wrote:
> > > 
> > > [ Charset UTF-8 unsupported, converting... ]
> > > > 
> > > > 
> > > > Author: trasz
> > > > Date: Sat Jul??8 11:06:27 2017
> > > > New Revision: 320803
> > > > URL: https://svnweb.freebsd.org/changeset/base/320803
> > > > 
> > > > Log:
> > > > ? Fix "mount -uw /" when the filesystem type doesn't match.
> > > > ??
> > > > ? This basically makes "mount -uw /" work when the filesystem
> > > > ? mounted on / is NFS, but the one configured in fstab(5) is
> > > > UFS,
> > > > ? which can happen when you forget to modify fstab.
> > > Please do not silence user errors because they are inconvinient,
> > > this is a configuration error and the system should fail to?
> > > mount the incorrectly configured root.
> > > 
> > > If we start changing things to silently ignore user configuration
> > > errors we are going down a very slippery road.
> > > 
> > IMO, this change fixes the right problem, but maybe does so the
> > wrong
> > way. ?Mount -u is by definition an update to an existing mount.
> > ?There
> > should be no need to consult /etc/fstab for an existing mount since
> > the
> > info is available from the kernel.
> > 
> > Note that I say the foregoing with my user hat on. ?I haven't
> > looked at
> > the code to see if there's some reason why my common-sensical way
> > of
> > thinking about it is actually impossible to implement for some
> > reason.
> This "check" saves one from the mistake of a wrong fstab that was
> not properly written for nfs that is probably going to blow up when
> it goes to get /usr or some other file system.  
> 
> Example of when this change can cause things to go very wrong for
> an admin.
> 
> I rsync/however a system that is booting from disk onto my nice new
> NAS box and setup exports of the file systems that I moved.  I
> further
> set up dhcp/tftp/pxe to boot this NFS version of the system.
> 
> I forget to edit the etc/fstab in the copy on the NFS server.
> 
> I reboot the system via PXE, it gets its root file system via NFS
> and now silently ignores my error and procededs to FFS mount all
> the other file system.
> 
> Can you see the error in thinking this change is a good idea?

What I see is you ignoring everything I said and ranting about
something completely different.  I sure don't have the energy to get
involved in that kind of craziness, so just pretend I never said
anything at all.

-- Ian