Making a bootable backup (hard)disk... how?

Daniel Feenberg feenberg at
Sun Jun 10 23:10:45 UTC 2012

On Sun, 10 Jun 2012, Ronald F. Guilmette wrote:

> What I don't understand (and what I wish someone would enlighten me about)
> is just this:  It would seem that in order to implement these dump levels,
> dump must be keeping a record somewhere, for each file in the filesystem,
> of the level at which that file was last dumped.  But where is this infor-
> mation stored, exactly??  I won't be able to sleep until I know.

Only the dates of the levels of backup are stored, in /etc/dumpdates. 
Then the fact that a file has been dumped is inferred by comparing the 
file's last mod date with the dates in /etc/dumpdates. See the -T and -u 
options of the dump man page where this is implied but perhaps not 
actually stated.

It does occur to me that /etc is not a felicitous place to keep this 
information, but given the desirability of dumping filesystems in read 
only state, placing the dump dates in the filesystem itself isn't 

daniel feenberg

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