RE: Live Upgrade for Linux
From: Glynn Clements (glynn.clements@virgin.net)
Date: 04/08/03
- Previous message: Seth Arnold: "Re: Red Hat: To patch or to upgrade?"
- In reply to: Octavio / Super: "RE: Live Upgrade for Linux"
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From: Glynn Clements <glynn.clements@virgin.net> Date: Tue, 8 Apr 2003 21:11:52 +0100 To: Octavio / Super <alvarezp@telnor.net>
Octavio / Super wrote:
> Regarding disk images, what about the data that is in the RAM that
> hasn't yet been written to disk? If you clone with cp or tar it
> wouldn't be much of a problem, but I was thinking on something like dd
> for cloning the hard disk. If dd tries to read something from the
> device, does Linux realizes that and syncs the disk before the read
> operation?
No. The read operations will read from the not-yet-sync'd memory copy,
so you still get the same result.
However, copying a "live" filesystem (one which is currently mounted
read/write) is unsafe however you do it, whether by tar, cp, dd or
whatever. If you wish to duplicate a filesystem, you first have to
unmount it or mount it read-only (obviously, an unmounted filesystem
can't be duplicated by tar or cp).
-- Glynn Clements <glynn.clements@virgin.net>
- Previous message: Seth Arnold: "Re: Red Hat: To patch or to upgrade?"
- In reply to: Octavio / Super: "RE: Live Upgrade for Linux"
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