Copying file systems

[William Roberts;]

In <5444 at dftsrv.gsfc.nasa.gov> jim at jagubox.gsfc.nasa.gov (Jim Jagielski) 
writes:

>}These aren't flaws with the dump method. They are BUGS with the dump and
>}restore programs. Better read up on that SPR stuff.
>}

>Oh great... and what other bugs are there in dump/restore? Must I list every
>file on my system and make sure that the owner, group and modes are correct?
>Did dump/restore not copy other files and "forget" to tell me? Should I stay
>awake at night pondering the REAL status of my new system??

Yes and no.

In any hybrid system such as A/UX, where you import code and facilities from 
two radically different sources, there is a possibility that not quite 
everything got merged properly. The dump/restore/cpio/tar facilities seem to 
have been quite badly hit by all this, specifically:

SYSV - FIFOs, short filenames, effective group id used during file creation
       cpio, SYSV version of dump & tar
BSD  - symbolic links, long names, UNIX domain sockets, group id of parent
       directory used during file creation, BSD version of dump & tar

In A/UX 1.1 there were bugs in the way that cpio (SYSV) handled symbolic links 
(BSD). The old SASH version of fsck didn't understand UNIX domain sockets.
There is a fundamental design problem with tar in that it limits pathnames to 
1023 bytes (or thereabouts), which isn't long enough if people have Mac 
filesystems on top of BSD filesystems (e.g. using CAP) and they go in for 
meaningful names.

It is disturbing when archiving utilities don't work properly, but these 
programs are generally pretty paranoid and so they don't keep quiet about your 
problems: the worst I've encountered was the cpio bug with symlink handling, 
which could actually end up changing the permissions on your *original* files 
to something like 777, but this has been fixed in 2.0 (maybe even 1.1.1).

PS. That "pax" program suffers from an assortment of these bugs, and 
furthermore it doesn't really behave the same way as either cpio or tar. I 
used to have cpio and tar as symbolic links to pax, but eventually went back 
to the real things.
--

William Roberts                 Internet:  liam at dcs.qmw.ac.uk
Queen Mary & Westfield College  UUCP:      liam at qmw-dcs.UUCP
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