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Re: Idea: a way to use /dev/modem symlinks safely

On Sat 10 Apr 1999, Wichert Akkerman wrote:
> Previously Avery Pennarun wrote:
> > Here's my thought:  rather than creating a lockfile for the filename of the
> > requested device (eg. /dev/modem --> /var/lock/LCK..modem) we can create a
> > lockfile for the target of the symlink (eg. /dev/modem --> /dev/ttyS2 -->
> > /var/lock/LCK.ttyS2).
> There has been some discussion about this on the FHS list, and the
> issue has recently come up again. The consensus seems to be to use
> a liblockfile which makes the lockfile using the real devicename,
> and perhaps a symlink with the other name as well.

FWIW I like the way SVR4 does it (one of the few things it gets right :-),
it uses the major / minor device number and the st_dev major number of
the fs containing /dev.  That way it doesn't matter via what name the
device is referenced; it's the major and minor numbers that are important
here. The lockfile contains the pid of the locking process as "%10d\n"

Paul Slootman
home: paul@wurtel.demon.nl | work: paul@murphy.nl | debian: paul@debian.org
http://www.wurtel.demon.nl | Murphy Software,   Enschede,   the Netherlands

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