> Implement expansion of special "magic" strings in symlinks into
> system-specific values.  Submitted by Chris Demetriou in Nov 1995 (!)
> in PR kern/1781, modified only slighly by me.
> 
> This is enabled on a per-mount basis with the MNT_MAGICLINKS mount
> flag.  It can be enabled at mountroot() time by building the kernel
> with the ROOTFS_MAGICLINKS option.
> 
> The following magic strings are supported by the implementation:
> 
> 	@machine	value of MACHINE for the system
> 	@machine_arch	value of MACHINE_ARCH for the system
> 	@hostname	the system host name, as set with sethostname()
> 	@domainname	the system domain name, as set with setdomainname()
> 	@kernel_ident	the kernel config file name
> 	@osrelease	the releaes number of the OS
> 	@ostype		the name of the OS (always "NetBSD" for NetBSD)

is there any os which uses the compatible semantics with this?
why don't you follow the existing conventions like tru64 cdsl or
dragonfly varsym?

YAMAMOTO Takashi