Specifically for the library files:

The libraries are marked by major and minor number.  Programs can use 
a newer "minor number"ed library.  For example, libc.so.20.1 and 
libc.so.20.10 can both be used by a program that wants libc.20.1.  
The reverse is not true, however.  If a program needs 20.10, the
20.1 library simply will not do.

So, in general*, it is safe to remove minor version updated files.
In our example above, we would expect libc.20.1 to be completely 
included in libc.so.20.10, so 20.1 could be deleted.  Note that part
of the installation process will link libc.so.20 and libc.so to 
libc.so.20.10, so anything that just uses major numbers for linking 
will continue to 'just work'.

Dave

*Note:  This is the way it's supposed to work, and I've never had
a problem with it in the past 10 years or so.  Of course, there's 
always some human error horror story somewhere, so you might want
to keep a copy of the old library around on a tape or an old CD 
somewhere, just in case.

Donald Lee wrote:
> 
> I have below the list of files in 1.5 that are not in 1.5.2, with
> the name of the distribution tarball prepended.  My plan is to delete
> these files when the 1.5.2 upgrade is done.
> 
> Can anyone tell me about the implications of the /usr/lib/*.so.#.# files?
> I'm guessing that the suffixes numbers are some sort of version.  Is
> there a reason that I should leave the old ones in place?
> 
> TIA,
> 
> -dgl-
> 
> P.S. Interesting that the "pim6*" stuff was removed. ;->
> 
> base1.5         ./etc/openssl/cert.pem
> base1.5         ./usr/lib/libasn1.so.2
> base1.5         ./usr/lib/libasn1.so.2.0
> base1.5         ./usr/lib/libcom_err.so.3.0
> base1.5         ./usr/lib/libgssapi.so.0
> base1.5         ./usr/lib/libgssapi.so.0.4
> base1.5         ./usr/lib/libhdb.so.4
> base1.5         ./usr/lib/libhdb.so.4.1
> base1.5         ./usr/lib/libkadm5clnt.so.5
> base1.5         ./usr/lib/libkadm5clnt.so.5.1
> base1.5         ./usr/lib/libkadm5srv.so.6
> base1.5         ./usr/lib/libkadm5srv.so.6.0
> base1.5         ./usr/lib/libkafs.so.4.0
> base1.5         ./usr/lib/libkrb5.so.11
> base1.5         ./usr/lib/libkrb5.so.11.1
> base1.5         ./usr/lib/libroken.so.8
> base1.5         ./usr/lib/libroken.so.8.1
> base1.5         ./usr/lib/libsl.so.1.0
> base1.5         ./usr/lib/libss.so.3.0
> base1.5         ./usr/lib/libtelnet.so.3.0
> base1.5         ./usr/sbin/mtrace6
> base1.5         ./usr/sbin/pim6dd
> base1.5         ./usr/sbin/pim6sd
> base1.5         ./usr/sbin/pim6stat
> 
> comp1.5         ./usr/include/krb5/kadm5_err.h
> 
> etc1.5          ./etc/dhclient-script
> etc1.5          ./etc/mail/sendmail-IPv4only.cf
> 
> man1.5          ./usr/share/man/cat1/pim6stat.0
> man1.5          ./usr/share/man/cat4/i386/ie.0
> man1.5          ./usr/share/man/cat5/pim6dd.conf.0
> man1.5          ./usr/share/man/cat5/pim6sd.conf.0
> man1.5          ./usr/share/man/cat8/mtrace6.0
> man1.5          ./usr/share/man/cat8/pim6dd.0
> man1.5          ./usr/share/man/cat8/pim6sd.0
> man1.5          ./usr/share/man/man1/pim6stat.1
> man1.5          ./usr/share/man/man4/i386/ie.4
> man1.5          ./usr/share/man/man5/pim6dd.conf.5
> man1.5          ./usr/share/man/man5/pim6sd.conf.5
> man1.5          ./usr/share/man/man8/mtrace6.8
> man1.5          ./usr/share/man/man8/pim6dd.8
> man1.5          ./usr/share/man/man8/pim6sd.8
> 
> misc1.5         ./usr/share/examples/supfiles/ftp.cs.umn.edu
> misc1.5         ./usr/share/examples/supfiles/sup.de.netbsd.org
> misc1.5         ./usr/share/examples/supfiles/sup.uk.netbsd.org
> misc1.5         ./usr/share/sendmail/cf/netbsd-proto-IPv4only.mc
> 
> xcomp1.5        ./usr/X11R6/man/cat3/X.0
> xcomp1.5        ./usr/X11R6/man/cat3/XConsortium.0
> xcomp1.5        ./usr/X11R6/man/cat3/XStandards.0
> xcomp1.5        ./usr/X11R6/man/cat3/Xsecurity.0