On Wed, 21 Dec 2016 21:46:54 +0100 Geert Stappers <[email protected]> wrote: > On Wed, Dec 21, 2016 at 10:04:36AM +0100, Philip Hands wrote: > > Philipp Kern <[email protected]> writes: > > > On 12/20/2016 09:26 PM, Geert Stappers wrote: > > >> On Mon, Dec 19, 2016 at 10:00:57PM +0100, Geert Stappers wrote: > > >> Goal is having a "header" which make it possible > > >> to check that actual a preseed file is being downloaded. > > >> > > >> What are the opinions about a two step approach like > > >> > > >> Step 1: > > >> Document all "stretch" preseed files begining with '#!preseedV1' > > >> > > >> Step 2: > > >> In "stretch+1", a.k.a. "buster", implement code that checks '#!preseedV1' > > >> and informs user when not found. > > > > > > How would this change the outcome of the bug you encountered? If I > > > understand you correctly it told you that the file was corrupt. Your > > > proposal would just re-enforce that notion, at the expense of everyone > > > needing to change their files? :) > > > > This seems only to be an issue when using PXE booting, and is likely to > > be particularly problematic when one does not have full control of the > > DHCP server, or where it cannot be persuaded to offer different files to > > different DHCP clients. > > IIRC is the check (http:|ftp:|https:) in the bootfilename. > Default protocol is TFTP. Doesn't need a URL syntax. > > I expect there will be more URLs in DHCP bootfilename parameter. > More bootloaders then iPXE will get support for HTTP netboot. > > > > The problem is then that a non-preseed file may be offered in a way that > > tricks d-i into trying to load it, at which point it will throw an > > error. > > > > So, how about this: > > > > We have a debconf value to select the severity of the error when > > failing to recognise the format of a preseed file. > > > > Normally, that should default to "error", as is now the case. > > > > For DHCP preseeding, the default should be changed to something less > > severe ("warn" or "ignore"). > > > > We could then have something as a header, as you suggest, which could > > be used to decide to set the severity back to "error" if it is seen in > > a DHCP preseed file. > > > > That way, all non-DHCP preseeding could continue just as it is now. > > AFAIK can't see preseed, the programma reads the preseed file > sets debconf setting, how it is invoked. > Hence my request for magic. Magic this time being an identification header. > > > > If one wants corrupt preseed files to throw an error, even when DHCP-ed, > > then adding the header will achieve that (except when the header is > > corrupted). > > > > If one gets given the wrong sort of file via DHCP then it'll get > > ignored or throw a warning. > > > > We could at some point add another value for the severity setting, of > > "magicrequired" that would implement the behaviour that Geert seems to > > be advocating: > > throwing an error if file is seen that lacks magic. > > > > (that could perhaps become the default for DHCP preseeding, but > > otherwise I doubt it's useful enough to render all existing preseed > > files broken.) > > I support Philipp Kern point "avoid breaking existing preseed files". > > With magic can a preseedfile be identified. Result of the ID check > can (and should) be used in further program flow. Used wisely. > > > > > Cheers, Phil. > > > > P.S. I don't think that using #! as part of the magic string is a great > > idea -- it will make people incorrectly assume that there is an > > interpreter being invoked somewhere. > > New proposed magic string: '#_preseed_V1'
Hi! Any progress on this particular problem? I fully agree that pressed file should be identifiable by either some magic line or header. -- Pali Rohár [email protected]
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