Date: Mon, 06 Nov 2006 02:11:54 +0100 From: Pawel Worach <pawel.worach@gmail.com> To: Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org> Cc: freebsd-hackers@freebsd.org, xdivac02@stud.fit.vutbr.cz, bu7cher@yandex.ru, jwd@FreeBSD.org, joel@FreeBSD.org Subject: Re: Yet another magic symlinks implementation Message-ID: <454E8BDA.9030304@gmail.com> In-Reply-To: <17741.9196.102826.208010@bhuda.mired.org> References: <454C55BD.000003.22283@webmail11.yandex.ru> <17741.9196.102826.208010@bhuda.mired.org>
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Mike Meyer wrote: > In <454C55BD.000003.22283@webmail11.yandex.ru>, Andrey V. Elsukov <bu7cher@yandex.ru> typed: >> Hi, All! >> >> I've ported NetBSD magic symlinks implementation to FreeBSD. >> The description of magiclinks can been found here: >> http://www.daemon-systems.org/man/symlink.7.html > > This kind of thing has been showing up in Unix variants for a couple > of decades, but none have have ever caught on. Can you provide some > examples of what this is being used for? > An interesting use for this is found in an commercial embedded platform where a system image is selected with a @sys variable symlink. This is used for live upgrades (and fast backouts or test boots) of the platform where a new image is extracted from a .tgz to /image/$new_version and the @sys variable is likely updated by the boot loader for the next boot. # ls -l /usr lrwxr-xr-x 1 root wheel 8 Oct 3 13:32 /usr -> @sys/usr # cd /usr # pwd /image/OS-VERSION-BUILD-ID/usr Here a sysctl/kenv variable defines the @sys link target kern:@sys = image/OS-VERSION-BUILD-ID Regards -- Pawel
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