To find out what userland version you're running, you can do `cat
/etc/release`.

On a daily snapshot of NetBSD 4.0 BETA2, that results in the following for
example:

    
    
    $ cat /etc/release
    NetBSD 4.0_BETA2/amd64
    
    Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
        The NetBSD Foundation, Inc.  All rights reserved.
    Copyright (c) 1982, 1986, 1989, 1991, 1993
        The Regents of the University of California.  All rights reserved.
    
    Build settings:
              Build date   Sun Aug 26 03:02:56 UTC 2007
                Built by   builds@wb28
    
               BSDOBJDIR = '/usr/obj'
               BSDSRCDIR = '/usr/src'
                 BUILDID = '200708250002Z'
                 DESTDIR = '/home/builds/ab/netbsd-4/amd64/200708250002Z-dest'
      EXTERNAL_TOOLCHAIN = (undefined)
                HAVE_GCC = '4'
                HAVE_GDB = '5'
         INSTALLWORLDDIR = (undefined)
             KERNARCHDIR = 'arch/amd64'
             KERNCONFDIR = '/home/builds/ab/netbsd-4/src/sys/arch/amd64/conf'
              KERNOBJDIR = '/home/builds/ab/netbsd-4/amd64/200708250002Z-obj/home/builds/ab/netbsd-4/src/sys/arch/amd64/compile'
              KERNSRCDIR = '/home/builds/ab/netbsd-4/src/sys'
                 MACHINE = 'amd64'
            MACHINE_ARCH = 'x86_64'
                    MAKE = '/home/builds/ab/netbsd-4/amd64/200708250002Z-tools/bin/nbmake'
                MAKECONF = '/home/builds/etc/make.conf'
               MAKEFLAGS = ' -d e -m /home/builds/ab/netbsd-4/src/share/mk 
    -d e -m /home/builds/ab/netbsd-4/src/share/mk -j 1 
    -J 15,16 HOST_OSTYPE=NetBSD-4.0_BETA2-i386 MKOBJDIRS=yes
     NOPOSTINSTALL=1 USETOOLS=yes _SRC_TOP_=/home/builds/ab/netbsd-4/src 
    _SRC_TOP_OBJ_=/home/builds/ab/netbsd-4/amd64/200708250002Z-obj/home/builds/ab/netbsd-4/src _THISDIR_=etc/'
              MAKEOBJDIR = (undefined)
        MAKEOBJDIRPREFIX = '/home/builds/ab/netbsd-4/amd64/200708250002Z-obj'
             MAKEVERBOSE = '0'
                   MKBFD = 'yes'
              MKCATPAGES = 'yes'
                MKCRYPTO = 'yes'
           MKCRYPTO_IDEA = 'no'
           MKCRYPTO_MDC2 = 'no'
            MKCRYPTO_RC5 = 'no'
                   MKCVS = 'yes'
                 MKDEBUG = 'no'
              MKDEBUGLIB = 'no'
                   MKDOC = 'yes'
           MKDYNAMICROOT = 'yes'
                   MKGCC = 'yes'
               MKGCCCMDS = 'yes'
                   MKGDB = 'yes'
                MKHESIOD = 'yes'
               MKHOSTOBJ = (undefined)
                  MKHTML = 'yes'
                MKIEEEFP = 'yes'
                 MKINET6 = 'yes'
                  MKINFO = 'yes'
              MKIPFILTER = 'yes'
              MKKERBEROS = 'yes'
               MKLINKLIB = 'yes'
                  MKLINT = 'yes'
                   MKMAN = 'yes'
                  MKMANZ = 'no'
                   MKNLS = 'yes'
                   MKOBJ = 'yes'
               MKOBJDIRS = 'yes'
                   MKPAM = 'yes'
                    MKPF = 'yes'
                   MKPIC = 'yes'
            MKPICINSTALL = 'yes'
                MKPICLIB = 'yes'
               MKPOSTFIX = 'yes'
               MKPROFILE = 'yes'
                 MKSHARE = 'yes'
                  MKSKEY = 'yes'
             MKSOFTFLOAT = 'no'
             MKSTATICLIB = 'yes'
              MKUNPRIVED = 'yes'
                MKUPDATE = 'yes'
                  MKUUCP = (undefined)
                   MKX11 = 'yes'
                    MKYP = 'yes'
              NBUILDJOBS = (undefined)
            NETBSDSRCDIR = '/home/builds/ab/netbsd-4/src'
              NOCLEANDIR = (undefined)
           NODISTRIBDIRS = (undefined)
              NOINCLUDES = (undefined)
              OBJMACHINE = (undefined)
              RELEASEDIR = '/home/builds/ab/netbsd-4/amd64/200708250002Z-rlse'
       TOOLCHAIN_MISSING = 'no'
                 TOOLDIR = '/home/builds/ab/netbsd-4/amd64/200708250002Z-tools'
                USETOOLS = 'yes'
          USR_OBJMACHINE = (undefined)
               X11SRCDIR = '/home/builds/ab/netbsd-4/xsrc'
    

If you're running a mix and match of userland, kernel, and individual userland
apps with cherry-picked CVS revisions, the [[ident]] program may be used to
find the revisions of the individual source files a binary was composed of:

    
    
    $ ident `which which`                      
    /usr/bin/which:
         $ NetBSD: crt0.c,v 1.4 2004/08/26 21:23:06 thorpej Exp $
         $ NetBSD: whereis.c,v 1.18 2006/07/30 11:50:29 martin Exp $