Accounting changes

[Robert Watson]

On Thu, 19 Apr 2007, Robert Watson wrote:

> If we're willing to assume architectures can only read their own accounting 
> files (the status quo), the above argument doesn't really make sense.  You 
> end up with a series of versions of "struct acct", and that code is 
> architecture-neutral.  Thinking about it more, I'm not sure a per file 
> header is even required or desired (as I had previously suggested), simply a 
> per-record versioning scheme, allowing a reboot onto a new kernel to 
> continue to write to the existing accounting data.  Read the first 16 bytes, 
> if the first byte is non-0 then it's the original "struct acct" layout, and 
> otherwise the second byte is the version number to use.  Or in the interests 
> of forward compatibility, include a length parameter in another 16 bytes so 
> you can skip over records if necessary in order to allow the kernel to move 
> back and forward across file versions if there's a problem after the 
> upgrade.

s/16 bytes/16 bits/ was intended in the above. :-)

Robert N M Watson
Computer Laboratory
University of Cambridge