Gentoo Archives: gentoo-user

From: Michael Schreckenbauer <grimlog@×××.de>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] udev + /usr
Date: Mon, 12 Sep 2011 17:51:54
Message-Id: 1469353.CZnlx9uQzD@pc
In Reply to: Re: [gentoo-user] udev + /usr by Alan Mackenzie
1 Hi Alan,
2
3 On Monday, 12. September 2011 17:17:37 Alan Mackenzie wrote:
4 > Hi, Michael.
5 >
6 > On Mon, Sep 12, 2011 at 05:33:34PM +0200, Michael Schreckenbauer wrote:
7 > > Hi Alan,
8 > >
9 > > On Monday, 12. September 2011 15:02:48 Alan Mackenzie wrote:
10 > > > Hope nobody minds me starting a new thread with an accurate name.
11 > > >
12 > > > Which version of udev is it that has this nauseating feature of
13 > > > needing
14 > > > /usr loaded to boot?
15 > > >
16 > > > Somewhere in that version's source will be several (or lots of)
17 > > > "/usr".
18 > > > Just how difficult is it going to be to replace "/usr/bin" with
19 > > > "/bin"
20 > > > throughout the source?
21 > >
22 > > you misunderstood something. udev is able to run arbitrary scripts. Some
23 > > of those scripts are located in /usr/* or need something there. I doubt
24 > > you will find references to /usr in the udev-sources.
25 >
26 > Well, I'm a hacker. udev is free source, therefore fair game. I don't
27 > intend to put up with this nonsense without a fight. As far as I can
28 > make out, this is just one guy, Kay Sievers, who's on a power trip. Are
29 > there any indications at all that he actually talked to anybody in the
30 > wide world before making such a far reaching decision?
31 > On my current system, udev (164-r2) works without an earlily loaded /usr.
32 > Seemingly, later versions don't. That was why I was asking for somebody
33 > to identify one of these later versions for me.
34
35 it works for you, because your udev-rules need nothing from /usr/*
36 It's *not* udev requiring /usr, it's the scripts triggered by the rules.
37
38 > > > udev is part of the kernel.
39 > >
40 > > No. udev is usperspace.
41 >
42 > OK, udev is in userspace, _very_ _close_ to the kernel. ;-)
43 >
44 > > > How come the kernel hackers aren't up in arms about this as much as
45 > > > we are? Or are they, maybe? In which case, maybe the kernel people
46 > > > would welcome an option to disrequire the early mounting of /usr as
47 > > > much as we would.
48 > > >
49 > > > Anyhow, I'd like to take a peek at the source code which does this
50 > > > evil
51 > > > thing. Would somebody please tell me which version of udev is
52 > > > involved.>
53 > > Every udev version works this way.
54 >
55 > My udev (164-r2) is just fine at the moment. I'm not sure what you mean
56 > by that statement.
57
58 It works for you.
59 Every udev-version I know of, is able to run any script you like it to.
60
61 > > Fixing udev to continue working with separate /usr is far from trivial
62 > > imo. Changing some paths is not the way to go for sure.
63 >
64 > Maybe, maybe not.
65
66 No, I wrote "for sure", because I *know* this.
67
68 > But it seems a changing of paths (/ -> /usr) is
69 > precisely what is breaking newer udevs.
70
71 No, it is *not*
72
73 > It might be possible to change
74 > them back. This could involve moving a fair amount of stuff from /usr to
75 > /, but not half as much as moving the entire /usr partition.
76
77 Again, udev can run arbitrary scripts.
78
79 > > First of all, udev has to distinguish between "device not present" and
80 > > "script error of some kind". Failing scripts have to be queued somehow
81 > > for later execution. If a script keeps failing, it has to be removed
82 > > from that queue, with a message to syslog or something like that. If
83 > > udev needs a script in /usr/* to mount /usr then there's a
84 > > chicken-egg-problem, which could be hard to solve (if possible at all
85 > > without moving things from /usr/ to /). Note, that I am wild guessing
86 > > here, I did not study the udev sources or any related script/rule :)
87 >
88 > This sounds like a separate (if related) problem.
89
90 No, this *is* the problem.Canek has posted some links in the other thread,
91 some other guy, I have forgotten who it was, posted others. If interested read
92 them. I really don't want to offend you, but unless you understand, how things
93 work and what the problem is, don't waste your time looking at udev's sources.
94
95 Best,
96 Michael

Replies

Subject Author
Re: [gentoo-user] udev + /usr Alan Mackenzie <acm@×××.de>