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Re: "Write once only but read many" filesystem



Jörn Engel wrote:
On Sat, 22 March 2008 23:55:53 +0800, Peter Teoh wrote:
  Or do you want individual files/directories to be immutable - chattr?
chattr is not good enough, as root can still modify it.   So if
current feature is not there, then some small development may be
needed.

 And in either case, what problem do you want to solve with a read-only filesystem?
Simple:   i want to record down everything that a user does, or a
database does, or any applications running - just record down its
state permanently securely into the filesystem, knowing that for sure,
there is not way to modify the data, short of recreating the
filesystem again.    Sound logical?   Or is there any loophole in this
concept?

The loophole is called root.  In a normal setup, root can do anything,
including writing directly to the device your filesystem resides in,
writing to kernel memory, etc.

It may be rather inconvenient to change a filesystem by writing to the
block device, but far from impossible.  If you want to make such changes
impossible, you are facing an uphill battle that I personally don't care
about.  And if inconvenience is good enough, wouldn't chattr be
sufficiently inconvenient?

Jörn


How about mounting an isofs via loopback? This has the added benefit of being ready to be exported to disc. You can make it with mkisofs on a directory structure and mount it to the tree with a normal mount(1). If it asks for fs type on mount, I think its 'iso9660'.


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