What you're describing is (if Wikipedia is to be believed) the behavior specified by POSIX:
http://en.wikipedia.org/wiki/Stat_%28system_call%29#Criticism_of_atime Dave On Wed, Dec 04, 2013 at 10:37:27PM -0500, Alex Aminoff wrote: > On 12/4/2013 10:21 PM, Matt Simmons wrote: > > My knowledge is somewhat limited to the Linux world, but in my > > experience I've never seen a mount be set to 'ro' and have anything > > updated. I hate to use the term 'flabbergasted', but I'm pretty sure > > that if I saw an implementation that didn't respect the 'ro' flag, I'd > > be at the very least 'put out', and perhaps even vitriolic. > > > Yeah, flabbergasted is a good description of how I felt. > > Nevertheless, I tested it and unless I messed up my test, an NFS mount > with -o ro, you read a file on the mounted FS, and the access time is > updated. > > For the test the server was a NetApp, the client was Linux. > > There is a mount flag -o noatime that does what I want. But I would > argue that this is not right. The simplest behavior - nothing is ever > written period - should be what you get by default, and then there could > be a flag that enables exceptional behavior, that is updating the access > time. > > I can squint and see why it would be the way it is. One perspective is > that the naive assumption is that reading off a RO filesystem should be > just like reading any other way; when you read, the OS conveniently > remembers when you did. The inconsistency of "writing" to a read-only > thing is less important than the inconsistency of not updating the > access time when the file is read. > > But what if the underlying device is not capable of recording access > times, like a CD-ROM? Can you look at the mount options and see that a > CDROM is read-only? But then you can't know whether access times will be > updated unless you use some other method to find out what the underlying > device is. So that's an abstraction violation. Bother, I don't have a > unix box easily to hand where I can check what the mount options on a > CDROM look like. > > I'm not sure if this is just grousing, or flame bait, or a gotcha that > every sysadmin should know because there is no way to anticipate it. > > - Alex > > > --Matt > > > > > > > > On Tue, Dec 3, 2013 at 2:21 PM, Alex Aminoff <[email protected] > > <mailto:[email protected]>> wrote: > > > > > > Hi folks. I encountered something odd. > > > > Suppose you mount a file system read only. You read a file from > > it. Does > > the access time of that file get updated? > > > > In one place I found documentation saying no. But other places seem to > > imply that it does. > > > > Does the answer change if it is an NFS mount? > > > > I have deliberately left details of what OS I'm using out, because it > > seems to me that the answer should be consistent, and if it is not, it > > should be documented publicly. > > > > - Alex Aminoff > > BaseSpace.net, NBER > > > > > > > > > > _______________________________________________ > > bblisa mailing list > > [email protected] <mailto:[email protected]> > > http://www.bblisa.org/mailman/listinfo/bblisa > > > > > > > > > > -- > > "Today, vegetables... Tomorrow, the world!" > > > > > > _______________________________________________ > > bblisa mailing list > > [email protected] > > http://www.bblisa.org/mailman/listinfo/bblisa > > _______________________________________________ > bblisa mailing list > [email protected] > http://www.bblisa.org/mailman/listinfo/bblisa _______________________________________________ bblisa mailing list [email protected] http://www.bblisa.org/mailman/listinfo/bblisa
