Profile

Cover photo
Philipp Kern
Works at Google
Attended Karlsruhe Institute of Technology
Lives in München, Germany
236 followers|304,053 views
AboutPostsCollections

Stream

Philipp Kern

Shared publicly  - 
 
Ob das Tarifeinheitsgesetz wohl gekommen wäre, wenn die Politiker im Bundestag einen Tarifvertrag und mehrere Gewerkschaften gehabt hätten?
 ·  Translate
1
Roland Mieslinger's profile photo
 
Vermutlich nicht, da niemand einen Streik im Bundestag bemerken würde.
Wenn sich aber niemand aufregt, herrscht auch kein Handlungsbedarf.
 ·  Translate
Add a comment...

Philipp Kern

Shared publicly  - 
 
Huch. Und was waren dann die verbeamteten Lokführer? Money quote: "Damit sollte verhindert werden, dass der Staat in Arbeitskämpfen grundsätzlich bessergestellt sei als private Arbeitgeber, die ja keine Beamten haben und deshalb niemanden zwingen können, als Streikbrecher zu arbeiten." Ja, genau, das passiert auch gerade überhaupt nicht bei der Bahn.
 ·  Translate
Im Arbeitskampf mit der Gewerkschaft Ver.di setzt die Deutsche Post offenbar Beamte als Streikbrecher ein. Das Bundesverfassungsgericht hat diese Praxis eigentlich verboten, der Konzern sieht sich dennoch im Recht.
1
Jon Bright's profile photoPhilipp Kern's profile photo
2 comments
 
+Jon Bright​ Es wurden noch nach der Privatisierung Lokführer verbeamtet? Ich dachte die wären alle aus der Zeit des Staatsbetriebs (siehe auch Ost/West-Impact).

Bei den Lokführern kann man einfach den Dienstplan ändern und bei der Post muss man vermutlich die Abordnung ändern? Wie dem auch sei, das damalige Urteil war bestimmt auch aus einer Zeit in der es (noch) nur wenige Angestellte gab und deren Streiks deshalb ins Leere gingen.
 ·  Translate
Add a comment...

Philipp Kern

Shared publicly  - 
 
Beware of the Irish seems rather unfair. The people on the streets seem to be a lot more helpful and friendly here. Let's see if that impression survives the week and the Google melting pot. ;-)

(First time in Ireland and all.)
3
Ben Walton's profile photoIvan Vučica's profile photoPhilipp Kern's profile photo
3 comments
 
+Ivan Vučica Yes it is. They have beer. The weather is awesome. What sound I say... ;)

Well, except seeing the actual city center. I didn't manage to do that yet. :(
Add a comment...

Philipp Kern

Shared publicly  - 
 
Beware of the Irish… I guess? Hello, Dublin! :)

Very welcoming to me as a European with only one processing the passport check queue at the airport and processing ALL the Europeans first. Interestingly enough the officer only did a visual check on the identity card, not a computer check. Still, could be better. Could be Schengen. ;-)
2
andrew mcmillan's profile photoPhilipp Kern's profile photo
2 comments
 
One week, leaving Saturday evening. Mainly in 1GC I guess. Open to lunch or else. ;-)
Add a comment...

Philipp Kern

Shared publicly  - 
 
I wonder why systemd didn't integrate a Linux installer yet. Would seem logical...
1
Julian Andres Klode's profile photoCristian Rodriguez's profile photoAndreas Jellinghaus's profile photoPhilipp Kern's profile photo
6 comments
 
Installing as a task requires to allocate space on a disk and telling the firmware where to find itself. You can play installer by modifying the firmware boot order and use a removable drive or network where you preconfigured things. But Windows to Go is not what I'm interested in. ;-)
Add a comment...

Philipp Kern

Shared publicly  - 
 
Google hat also laut Oettinger ein Quasi-Monopol. Und das, obwohl täglich Benutzer zu einer anderen Suchmaschine wechseln könnten. Als Quasi-Monopol solle man doch bitte keine eigenen Produkte bevorzugen. Gleichzeitig muss man der Telekom natürlich Überholspuren zugestehen, damit diese ihre eigenen Produkte (Entertain, Spotify) vermarkten kann. Wenn man dort wechseln will, dann dauert das anderthalb Monate und dazwischen hat man zwei Wochen kein Internet. Verkehrte Welt.
 ·  Translate
6
Michael Rother (Trminator)'s profile photoStephan S. (steini84)'s profile photo
2 comments
 
Google ist halt #Neuland 
 ·  Translate
Add a comment...

Philipp Kern

Shared publicly  - 
 
That awkward moment when you realize that your dpkg as invoked from debootstrap is torturing your disks because you put your files onto btrfs by hearing terrible, terrible HDD noises.
3
Andreas Jellinghaus's profile photoMaik Zumstrull's profile photoPhilipp Kern's profile photo
8 comments
 
Well, ZFS can write both intent log and l2arc to SSD. btrfs doesn't do such things (yet), which is a bit disappointing. (Especially as bcache has its header at the front, so is hard to enable if you avoided LVM.)

dpkg being pathologically bad is a different issue, I think. Basically one should just wrap the whole transaction within snapshots instead. (Of course there are some tricky bits to solve, but nothing too severe.)
Add a comment...
Have him in circles
236 people
Ólafur Jens Sigurðsson's profile photo
Bdale Garbee's profile photo
Yuriy Shapovalov's profile photo
Michael Biebl's profile photo
Thomas Glatt's profile photo
Peter M. Mumme's profile photo
Aleksandra Zdeb's profile photo
Wouter Verhelst's profile photo
Patricia Witzenrath's profile photo

Philipp Kern

Shared publicly  - 
 
If you don't learn from the past… Arch Linux has a single "linux" package. It also does not provide co-installability of multiple versions of a package. Of course that means that you end up with no fallback kernel if your shiny new bleeding edge kernel does not boot, because the old version is overridden. Now luckily this can be solved by accessing an old btrfs snapshot of the root filesystem from grub.

But it's not the only problem with that approach. You also cannot load any modules from the new kernel on the old. But the modules of the old kernel will disappear with the installation of the new. Then you end up with messages like "unknown filesystem 'ext3'". Or one cannot actually loop mount anything because the loop module wasn't loaded on boot.

Ubuntu solved most of these problems by simply bumping the package name with almost every release. Even if you have a bad release that did not do the version bump, you can rollback to an earlier ABI version. You then need to go and clean up obsolete versions and recompile modules quite often, but well, it works.

Debian stable has a similar problem as Arch in terms of modules and rollbacks: New modules are not compatible with old kernels even if the ABI version is supposed to be identical. So you can't load a new module either if the kernel package has been upgraded since the last boot. In theory you might be fall back to an older kernel, especially in testing and unstable, but on stable you have only one ABI version too and you don't generally get multiple entries in the boot menu. The only thing that works nicely with this approach is that old modules work on newer kernels and hence you do not need to recompile third-party modules as often.

And now I wonder what Fedora and RHEL do…
1
Evgeni Golov's profile photo
 
Fedora and RHEL support multiple versions installed. And yum/rpm will alsways install the new kernel, never upgrade, even if you tell it to do so (this was different in the past and a common mistake by not experienced admins).
Add a comment...

Philipp Kern

Shared publicly  - 
 
OpenBSD recently dropped support for MD5 $1$ hashes from crypt(3). That breaks their use in OpenSMTPD. (Maybe also in dovecot.) I did not store user's password in plain text before so this seems like an ignorant decision to me. It's not like I can suddenly generate Blowfish hashes from thin air. I wonder if it'd be better to just ditch OpenBSD or to write an LD_PRELOAD library that supports everything in crypt or to "fork" OpenSMTPD for my own purpose. (The latter being what they actually encourage.)
1
sven falempin's profile photoTony Sidaway's profile photoPhilipp Kern's profile photo
9 comments
 
+Tony Sidaway​ I already logged the passwords and blowfished them (thanks Dovecot). I still find it debatable if it's good to stop supporting old authentication data. OpenBSD and OpenSMTPd require more compromises from me but right now it still feels better to do the effort once. But I wonder if that attitude will burn me later.
Add a comment...

Philipp Kern

Shared publicly  - 
 
 
I don't think this fad will last. These liquid burning cars sound quite annoying and impractical...
In other languages: Swedish, German, Norwegian, Russian, Dutch Having heard so much good about petrol cars, we decided to test drive one. They are said to combine cheap price with long range and fast
13 comments on original post
1
Add a comment...

Philipp Kern

Shared publicly  - 
 
Scheduling production workloads on Google's server infrastructure is done using Borg. And it's all containers, since ages, using binary packages with minimal dependencies. The paper is quite detailled and IMO worth a read if you are interested in a very central piece of Google's data centers.
 
Google just released a paper about Borg, their system responsible for scheduling tasks in compute clusters with a large number of machines.

http://research.google.com/pubs/pub43438.html
Venue. Proceedings of the European Conference on Computer Systems (EuroSys), ACM, Bordeaux, France (2015). Publication Year. 2015. Authors. Abhishek Verma, Luis Pedrosa, Madhukar R. Korupolu, David Oppenheimer, Eric Tune, John Wilkes. BibTeX. @inproceedings{43438, title = {Large-scale cluster ...
3 comments on original post
4
Add a comment...

Philipp Kern

Shared publicly  - 
 
His observations about the usability of Bazel for open source projects are sadly true. When the Bazel team presented bits (it's largely created in Munich!) I also asked if we'd open source the Google runtime that we target internally. It's still different than how Linux distributions work, but at least one would have a hermetic target.

In the end the list of targets is ultimately what configuration decisions need to be based upon. "Ok, this is Linux amd64 with compiler A and libc Y, so let's activate configuration set X that includes feature set Y" is a good specification of a contract that you do not need to re-test with autotools every time you build a binary.

Blaze works as well as it does - for Google, -because there's a single unified codebase with all libraries checked in and few agreed upon and fixed system components. With that, you're correct as well as fast. As soon as you leave that hermetic boundary and try to access system libraries things get very messy.

I can totally see a Java environment with lots of different packages available through BUILD files that can be depended upon. (Probably versioned, so that you don't break builds.) I have a hard time imagining a Linux distribution environment that is similarly accessible to such a new build system.

As for Java used for Bazel: While it's significantly less portable than C, so is Go. Debian's testing approach by throwing so many architectures onto C code to find new exciting bugs is mainly necessary because C is badly specified and every architecture does it differently. If an architecture is actually used, it will have Java. (So does my BluRay player, just sayin'.) And resource consumption mostly depends on the working set you actually need, given that JVMs are heavily optimized these days.
 
On Bazel and Open Source
This is a rare post because I usually never talk about Google stuff here, and this post is about Bazel: a tool recently published by Google. Why? Because I love its internal counterpart, Blaze, and believe that Bazel has the potential to be one of the bes...
1 comment on original post
2
Will Beers's profile photoSebastian “tokkee” Harl's profile photoPhilipp Kern's profile photo
9 comments
 
Or allow hosts to be resolved via multicast DNS or lets localhost to be resolved via NSS.
Add a comment...
Philipp's Collections
People
Have him in circles
236 people
Ólafur Jens Sigurðsson's profile photo
Bdale Garbee's profile photo
Yuriy Shapovalov's profile photo
Michael Biebl's profile photo
Thomas Glatt's profile photo
Peter M. Mumme's profile photo
Aleksandra Zdeb's profile photo
Wouter Verhelst's profile photo
Patricia Witzenrath's profile photo
Work
Occupation
Site Reliability Engineer
Employment
  • Google
    Site Reliability Engineer, 2013 - present
    Corporate Engineering
  • Steinbuch Centre for Computing
    Studentische Hilfskraft, 2009 - 2013
    Network administration, IPv6 evangelist
  • Proventa AG
    Junior Consultant, 2011 - 2012
    Linux system administration
  • Karlsruhe Institute of Technology
    Studentische Hilfskraft, 2010 - 2011
    Mainframe administration (z/VM and Linux on a z10)
Places
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Currently
München, Germany
Previously
Karlsruhe, Germany - Neuried, Germany
Links
Other profiles
Contributor to
Story
Tagline
Coffee addict, Debian developer
Introduction
Disclaimer: Although I work for Google, my opinions and comments are my own and must not be interpreted as official statements.
Education
  • Karlsruhe Institute of Technology
    Diplom-Informatiker, 2006 - 2013
  • Grimmelshausen-Gymnasium Offenburg
    Abitur, 1997 - 2006
Basic Information
Gender
Male