<html><head></head><body>I'm thinking the atime is being updated by the server because the server accessed the file in order to serve it...<br><br><div class="gmail_quote">Alex Aminoff <alex@basespace.net> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">On 12/4/2013 10:21 PM, Matt Simmons wrote:<br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">My knowledge is somewhat limited to the Linux world, but in my <br />experience I've never seen a mount be set to 'ro' and have anything <br />updated. I hate to use the term 'flabbergasted', but I'm pretty sure <br />that if I saw an implementation that didn't respect the 'ro' flag, I'd <br />be at the very least 'put out', and perhaps even vitriolic.</blockquote><br />Yeah, flabbergasted is a good description of how I felt.<br /><br />Nevertheless, I tested it and unless I messed up my test, an NFS mount <br />with -o ro, you read a file on the mounted FS, and the access time is <br />updated.<br /><br />For the test the server was a NetApp, the client was Linux.<br /><br />There is a mount flag -o noatime that does what I want. But I would <br />argue that this is not right. The simplest be
havior
- nothing is ever <br />written period - should be what you get by default, and then there could <br />be a flag that enables exceptional behavior, that is updating the access <br />time.<br /><br />I can squint and see why it would be the way it is. One perspective is <br />that the naive assumption is that reading off a RO filesystem should be <br />just like reading any other way; when you read, the OS conveniently <br />remembers when you did. The inconsistency of "writing" to a read-only <br />thing is less important than the inconsistency of not updating the <br />access time when the file is read.<br /><br />But what if the underlying device is not capable of recording access <br />times, like a CD-ROM? Can you look at the mount options and see that a <br />CDROM is read-only? But then you can't know whether access times will be <br />updated unless you use some other method to find out what the underlying <br />device is. So that's an abstraction violation. Bother, I
don't
have a <br />unix box easily to hand where I can check what the mount options on a <br />CDROM look like.<br /><br />I'm not sure if this is just grousing, or flame bait, or a gotcha that <br />every sysadmin should know because there is no way to anticipate it.<br /><br />- Alex<br /><br /><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">--Matt<br /><br /><br /><br />On Tue, Dec 3, 2013 at 2:21 PM, Alex Aminoff <alex@basespace.net <br /><mailto:alex@basespace.net>> wrote:<br /><br /><br />Hi folks. I encountered something odd.<br /><br />Suppose you mount a file system read only. You read a file from<br />it. Does<br />the access time of that file get updated?<br /><br />In one place I found documentation saying no. But other places seem to<br />imply that it does.<br /><br />Does the answer change if it is an NFS mount?<br /><br />I have deliberately left details of what OS I'm using out, becau
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it<br />seems to me that the answer should be consistent, and if it is not, it<br />should be documented publicly.<br /><br />- Alex Aminoff<br /><a href="http://BaseSpace.net">BaseSpace.net</a>, NBER<br /><br /><br /><br /><br /><hr /><br />bblisa mailing list<br />bblisa@bblisa.org <mailto:bblisa@bblisa.org><br /><a href="http://www.bblisa.org/mailman/listinfo/bblisa">http://www.bblisa.org/mailman/listinfo/bblisa</a><br /><br /><br /><br /><br />-- <br />"Today, vegetables... Tomorrow, the world!"<br /><br /><br /><hr /><br />bblisa mailing list<br />bblisa@bblisa.org<br /><a href="http://www.bblisa.org/mailman/listinfo/bblisa">http://www.bblisa.org/mailman/listinfo/bblisa</a></blockquote><br /><hr /><br />bblisa mailing list<br />bblisa@bblisa.org<br /><a href="http://www.bblisa.org/mailman/listinfo/bblisa">http://www.bblisa.org/mailman/listinfo/bblisa</a><br /></pre></blockquote></div><br>
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