Date: Wed, 31 Jul 2002 12:20:34 -1000 From: Clifton Royston <cliftonr@lava.net> To: stable@FreeBSD.org Subject: New install options -C and -S in combination? Message-ID: <20020731122034.A14334@lava.net>
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The -C (conditional?) option to install sounds close to what I have
been wanting in some respects; so does -S (safe copy). Unfortunately
the man page documentation is not quite clear enough for me to
understand how these work and whether they can be used together.
1) If install with the -C option finds the destination and target files
are identical, will it actually rewrite the data on top of the existing
one as the man page seems to imply? Or does it recognize this as a
no-op and do nothing? If install -C finds the destination files are
not identical, will it copy the new contents on top of the target file
in place (preserving the inode though changing the modification time)?
2) Can the -S option be combined with the -C option to ensure safe
(atomic) updates of those files which need to be updated? Would this
have the desired behavior that files which are identical are left
alone, but files which must be updated are updated atomically?
This last question is much on my mind at the moment, as we
accidentally crashed a running server yesterday, apparently due to an
install script for OpenSSL doing a non-atomic update of its libssl
while it was in use. (This was not a FreeBSD system, FWIW.)
I would like to have some combination of install options which has
the following properties:
1) Files which must be changed due to a difference are updated
atomically, so as to have the least likelihood of disrupting running
processes;
2) Files for which there is no difference between the destination and
target have both their inode and their modification time preserved, to
result in the minimum delta for a file intrusion detection system such
as Tripwire. (This would also be helpful in generating a list of what
binary updates necessarily resulted from an "installworld".)
I would wish for "install -C -S" to satisfy those properties, but it
is not clear to me from the man pages whether it does.
-- Clifton
--
Clifton Royston -- LavaNet Systems Architect -- cliftonr@lava.net
"What do we need to make our world come alive?
What does it take to make us sing?
While we're waiting for the next one to arrive..." - Sisters of Mercy
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