[Bug 267192] [NEW] Misleading cryptsetup error message

Colin Watson cjwatson at ubuntu.com
Wed Sep 10 23:12:14 BST 2008

On Wed, Sep 10, 2008 at 04:27:41PM +0200, Reinhard Tartler wrote:
> Milan Broz writes:
> > loading of dm_crypt is not cryptsetup job.
> >
> > Device-mapper has already autoloading of necessary target modules built in.
> > You just need device-mapper core initialized (dm_mod kernel module loaded).
> >
> > It just "simply works" on default configuration:
> >
> > # lsmod
> > Module                  Size  Used by
> > dm_mod                 48656  0
> I see, but couldn't cryptsetup at least warn if the running system has
> not even dm_mod loaded instead of indicating the user had entered a
> wrong passphrase?

Most tools that need a particular kernel feature modprobe the
corresponding module just in case (or check first and then modprobe, as
Alasdair mentions that lvm2 does). It would make sense for cryptsetup to
do this.

The wrong error message is clearly a bug, IMO. It's just poor error
handling (understandably, since presumably this is a situation not many
cryptsetup developers encounter, but even so).

> > Is it reproducible in other system? If not, it is some bug in Ubuntu
> > Live CD.
> You believe it is a bug if the Ubuntu live cd does not autoload dm_mod
> on startup? What do other ubuntu-developers think about this?

I disagree - there's no reason for the Ubuntu live CD to do so. dm-mod
is modular so that we don't have to load it when it isn't needed, and
the live CD doesn't need it.

I mean, of course we *could*, but in general programs that make fewer
assumptions about the system they're running on are more reliable so I
don't think it makes sense for the system to load kernel modules on the
off-chance that some program might need them. For example, we don't load
the kvm module on the off-chance that you might want to start up a
virtual machine; kvm takes care of doing that if you run it. From the
point of view of the Ubuntu live CD, dm-mod falls into much the same

Colin Watson                                       [cjwatson at ubuntu.com]

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