+ <div class="entry">
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/Detecting_NFS_hangs_on_Linux_without_hanging_yourself___.html">Detecting NFS hangs on Linux without hanging yourself...</a></div>
+ <div class="date"> 9th March 2017</div>
+ <div class="body"><p>Over the years, administrating thousand of NFS mounting linux
+computers at the time, I often needed a way to detect if the machine
+was experiencing NFS hang. If you try to use <tt>df</tt> or look at a
+file or directory affected by the hang, the process (and possibly the
+shell) will hang too. So you want to be able to detect this without
+risking the detection process getting stuck too. It has not been
+obvious how to do this. When the hang has lasted a while, it is
+possible to find messages like these in dmesg:</p>
+
+<p><blockquote>
+nfs: server nfsserver not responding, still trying
+<br>nfs: server nfsserver OK
+</blockquote></p>
+
+<p>It is hard to know if the hang is still going on, and it is hard to
+be sure looking in dmesg is going to work. If there are lots of other
+messages in dmesg the lines might have rotated out of site before they
+are noticed.</p>
+
+<p>While reading through the nfs client implementation in linux kernel
+code, I came across some statistics that seem to give a way to detect
+it. The om_timeouts sunrpc value in the kernel will increase every
+time the above log entry is inserted into dmesg. And after digging a
+bit further, I discovered that this value show up in
+/proc/self/mountstats on Linux.</p>
+
+<p>The mountstats content seem to be shared between files using the
+same file system context, so it is enough to check one of the
+mountstats files to get the state of the mount point for the machine.
+I assume this will not show lazy umounted NFS points, nor NFS mount
+points in a different process context (ie with a different filesystem
+view), but that does not worry me.</p>
+
+<p>The content for a NFS mount point look similar to this:</p>
+
+<p><blockquote><pre>
+[...]
+device /dev/mapper/Debian-var mounted on /var with fstype ext3
+device nfsserver:/mnt/nfsserver/home0 mounted on /mnt/nfsserver/home0 with fstype nfs statvers=1.1
+ opts: rw,vers=3,rsize=65536,wsize=65536,namlen=255,acregmin=3,acregmax=60,acdirmin=30,acdirmax=60,soft,nolock,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=129.240.3.145,mountvers=3,mountport=4048,mountproto=udp,local_lock=all
+ age: 7863311
+ caps: caps=0x3fe7,wtmult=4096,dtsize=8192,bsize=0,namlen=255
+ sec: flavor=1,pseudoflavor=1
+ events: 61063112 732346265 1028140 35486205 16220064 8162542 761447191 71714012 37189 3891185 45561809 110486139 4850138 420353 15449177 296502 52736725 13523379 0 52182 9016896 1231 0 0 0 0 0
+ bytes: 166253035039 219519120027 0 0 40783504807 185466229638 11677877 45561809
+ RPC iostats version: 1.0 p/v: 100003/3 (nfs)
+ xprt: tcp 925 1 6810 0 0 111505412 111480497 109 2672418560317 0 248 53869103 22481820
+ per-op statistics
+ NULL: 0 0 0 0 0 0 0 0
+ GETATTR: 61063106 61063108 0 9621383060 6839064400 453650 77291321 78926132
+ SETATTR: 463469 463470 0 92005440 66739536 63787 603235 687943
+ LOOKUP: 17021657 17021657 0 3354097764 4013442928 57216 35125459 35566511
+ ACCESS: 14281703 14290009 5 2318400592 1713803640 1709282 4865144 7130140
+ READLINK: 125 125 0 20472 18620 0 1112 1118
+ READ: 4214236 4214237 0 715608524 41328653212 89884 22622768 22806693
+ WRITE: 8479010 8494376 22 187695798568 1356087148 178264904 51506907 231671771
+ CREATE: 171708 171708 0 38084748 46702272 873 1041833 1050398
+ MKDIR: 3680 3680 0 773980 993920 26 23990 24245
+ SYMLINK: 903 903 0 233428 245488 6 5865 5917
+ MKNOD: 80 80 0 20148 21760 0 299 304
+ REMOVE: 429921 429921 0 79796004 61908192 3313 2710416 2741636
+ RMDIR: 3367 3367 0 645112 484848 22 5782 6002
+ RENAME: 466201 466201 0 130026184 121212260 7075 5935207 5961288
+ LINK: 289155 289155 0 72775556 67083960 2199 2565060 2585579
+ READDIR: 2933237 2933237 0 516506204 13973833412 10385 3190199 3297917
+ READDIRPLUS: 1652839 1652839 0 298640972 6895997744 84735 14307895 14448937
+ FSSTAT: 6144 6144 0 1010516 1032192 51 9654 10022
+ FSINFO: 2 2 0 232 328 0 1 1
+ PATHCONF: 1 1 0 116 140 0 0 0
+ COMMIT: 0 0 0 0 0 0 0 0
+
+device binfmt_misc mounted on /proc/sys/fs/binfmt_misc with fstype binfmt_misc
+[...]
+</pre></blockquote></p>
+
+<p>The key number to look at is the third number in the per-op list.
+It is the number of NFS timeouts experiences per file system
+operation. Here 22 write timeouts and 5 access timeouts. If these
+numbers are increasing, I believe the machine is experiencing NFS
+hang. Unfortunately the timeout value do not start to increase right
+away. The NFS operations need to time out first, and this can take a
+while. The exact timeout value depend on the setup. For example the
+defaults for TCP and UDP mount points are quite different, and the
+timeout value is affected by the soft, hard, timeo and retrans NFS
+mount options.</p>
+
+<p>The only way I have been able to get working on Debian and RedHat
+Enterprise Linux for getting the timeout count is to peek in /proc/.
+But according to
+<ahref="http://docs.oracle.com/cd/E19253-01/816-4555/netmonitor-12/index.html">Solaris
+10 System Administration Guide: Network Services</a>, the 'nfsstat -c'
+command can be used to get these timeout values. But this do not work
+on Linux, as far as I can tell. I
+<ahref="http://bugs.debian.org/857043">asked Debian about this</a>,
+but have not seen any replies yet.</p>
+
+<p>Is there a better way to figure out if a Linux NFS client is
+experiencing NFS hangs? Is there a way to detect which processes are
+affected? Is there a way to get the NFS mount going quickly once the
+network problem causing the NFS hang has been cleared? I would very
+much welcome some clues, as we regularly run into NFS hangs.</p>
+</div>
+ <div class="tags">
+
+
+ Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/sysadmin">sysadmin</a>.
+
+
+ </div>
+ </div>
+ <div class="padding"></div>
+
<div class="entry">
<div class="title"><a href="http://people.skolelinux.org/pere/blog/How_does_it_feel_to_be_wiretapped__when_you_should_be_doing_the_wiretapping___.html">How does it feel to be wiretapped, when you should be doing the wiretapping...</a></div>
<div class="date"> 8th March 2017</div>
<p>Next, the Federal Bureau of Investigation ask the Department of
Justice to go public rejecting the claims that Donald Trump was
wiretapped illegally. I fail to see the relevance, given that I am
-sure the surveillance industry in USA according to themselves believe
-they have all the legal backing they need to conduct mass surveillance
-on the entire world.</p>
+sure the surveillance industry in USA believe they have all the legal
+backing they need to conduct mass surveillance on the entire
+world.</p>
<p>There is even the director of the FBI stating that he never saw an
order requesting wiretapping of Donald Trump. That is not very
'the FBI denies any illegal wiretapping'. There is a fundamental and
important difference, and it make me sad that the journalists are
unable to grasp it.</p>
+
+<p><strong>Update 2017-03-13:</strong> Look like
+<a href="https://theintercept.com/2017/03/13/rand-paul-is-right-nsa-routinely-monitors-americans-communications-without-warrants/">The
+Intercept report that US Senator Rand Paul confirm what I state above</a>.</p>
</div>
<div class="tags">
- Tags: <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>.
+ Tags: <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/surveillance">surveillance</a>.
</div>
</div>
<div class="padding"></div>
- <div class="entry">
- <div class="title"><a href="http://people.skolelinux.org/pere/blog/Introducing_ical_archiver_to_split_out_old_iCalendar_entries.html">Introducing ical-archiver to split out old iCalendar entries</a></div>
- <div class="date"> 4th January 2017</div>
- <div class="body"><p>Do you have a large <a href="https://icalendar.org/">iCalendar</a>
-file with lots of old entries, and would like to archive them to save
-space and resources? At least those of us using KOrganizer know that
-turning on and off an event set become slower and slower the more
-entries are in the set. While working on migrating our calendars to a
-<a href="http://radicale.org/">Radicale CalDAV server</a> on our
-<a href="https://freedomboxfoundation.org/">Freedombox server</a/>, my
-loved one wondered if I could find a way to split up the calendar file
-she had in KOrganizer, and I set out to write a tool. I spent a few
-days writing and polishing the system, and it is now ready for general
-consumption. The
-<a href="https://github.com/petterreinholdtsen/ical-archiver">code for
-ical-archiver</a> is publicly available from a git repository on
-github. The system is written in Python and depend on
-<a href="http://eventable.github.io/vobject/">the vobject Python
-module</a>.</p>
-
-<p>To use it, locate the iCalendar file you want to operate on and
-give it as an argument to the ical-archiver script. This will
-generate a set of new files, one file per component type per year for
-all components expiring more than two years in the past. The vevent,
-vtodo and vjournal entries are handled by the script. The remaining
-entries are stored in a 'remaining' file.</p>
-
-<p>This is what a test run can look like:
-
-<p><pre>
-% ical-archiver t/2004-2016.ics
-Found 3612 vevents
-Found 6 vtodos
-Found 2 vjournals
-Writing t/2004-2016.ics-subset-vevent-2004.ics
-Writing t/2004-2016.ics-subset-vevent-2005.ics
-Writing t/2004-2016.ics-subset-vevent-2006.ics
-Writing t/2004-2016.ics-subset-vevent-2007.ics
-Writing t/2004-2016.ics-subset-vevent-2008.ics
-Writing t/2004-2016.ics-subset-vevent-2009.ics
-Writing t/2004-2016.ics-subset-vevent-2010.ics
-Writing t/2004-2016.ics-subset-vevent-2011.ics
-Writing t/2004-2016.ics-subset-vevent-2012.ics
-Writing t/2004-2016.ics-subset-vevent-2013.ics
-Writing t/2004-2016.ics-subset-vevent-2014.ics
-Writing t/2004-2016.ics-subset-vjournal-2007.ics
-Writing t/2004-2016.ics-subset-vjournal-2011.ics
-Writing t/2004-2016.ics-subset-vtodo-2012.ics
-Writing t/2004-2016.ics-remaining.ics
-%
-</pre></p>
-
-<p>As you can see, the original file is untouched and new files are
-written with names derived from the original file. If you are happy
-with their content, the *-remaining.ics file can replace the original
-the the others can be archived or imported as historical calendar
-collections.</p>
-
-<p>The script should probably be improved a bit. The error handling
-when discovering broken entries is not good, and I am not sure yet if
-it make sense to split different entry types into separate files or
-not. The program is thus likely to change. If you find it
-interesting, please get in touch. :)</p>
-
-<p>As usual, if you use Bitcoin and want to show your support of my
-activities, please send Bitcoin donations to my address
-<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&label=PetterReinholdtsenBlog">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
-</div>
- <div class="tags">
-
-
- Tags: <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/standard">standard</a>.
-
-
- </div>
- </div>
- <div class="padding"></div>
-
<p style="text-align: right;"><a href="index.rss"><img src="http://people.skolelinux.org/pere/blog/xml.gif" alt="RSS feed" width="36" height="14" /></a></p>
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<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/02/">February (3)</a></li>
-<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/03/">March (3)</a></li>
+<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/03/">March (4)</a></li>
</ul></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/chrpath">chrpath (2)</a></li>
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+ <li><a href="http://people.skolelinux.org/pere/blog/tags/debian">debian (148)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu (158)</a></li>
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+ <li><a href="http://people.skolelinux.org/pere/blog/tags/english">english (345)</a></li>
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- <li><a href="http://people.skolelinux.org/pere/blog/tags/surveillance">surveillance (47)</a></li>
+ <li><a href="http://people.skolelinux.org/pere/blog/tags/surveillance">surveillance (48)</a></li>
- <li><a href="http://people.skolelinux.org/pere/blog/tags/sysadmin">sysadmin (2)</a></li>
+ <li><a href="http://people.skolelinux.org/pere/blog/tags/sysadmin">sysadmin (3)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/usenix">usenix (2)</a></li>
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