pkg_add: Warning: package `digest-20121220' was built for a platform:
pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_RC4 (this host)
pkg_add: Warning: package `rpm2pkg-3.2.3' was built for a platform:
pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_RC4 (this host)
pkg_add: Warning: package `zip-3.0nb2' was built for a platform:
pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_RC4 (this host)
pkg_add: Warning: package `suse_base-12.1nb5' was built for a platform:
pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_RC4 (this host)
suse_base-12.1nb5: rebuilding run-time library search paths database
[1]   Abort trap              (/usr/pkg/emul/l...
suse_base-12.1nb5: populating /usr/pkg/emul/linux/dev
pkg_add: Warning: package `suse_compat-12.1' was built for a platform:
pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_RC4 (this host)
suse_compat-12.1: rebuilding run-time library search paths database
[1]   Abort trap              (/usr/pkg/emul/l...
===========================================================================
$NetBSD: MESSAGE.NetBSD,v 1.1.1.1 2012/03/21 13:35:50 obache Exp $

Do not forget to include COMPAT_LINUX in your kernel configuration file.
Linux binaries require this option in order to work.

Most Linux binaries also require procfs to be mounted with -o linux.
This can be automated by adding the following to your /etc/fstab:

procfs /emul/linux/proc procfs ro,linux

Some Linux binaries also require tmpfs to be mounted on /dev/shm.
This can be automated by adding the following to your /etc/fstab:

tmpfs /emul/linux/dev/shm tmpfs rw,-m1777

===========================================================================