http://output-dd.de/de/project/gastvortrag-richard-stallman

Handele stets so, dass Dir die öffentlichen Effekte Deines Handelns langfristig vertretbar erscheinen. Aber rechne damit, dass dies nichts nützt.

Ich behaupte jetzt einfach mal das selbst den meisten Informatikern (mich eingeschlossen) das nötige Verständnis für die Tragweite der meisten Entscheidungen die eigenen Daten betreffend fehlt. Nicht das wir es nicht könnten – wir denken nur nicht daran . . .

No space left on device – What GNU tools say

Together with btrfs OpenSuSE installs a tool called “snapper” which manages another feature of btrfs: snapshots. While this is actually great, it  really sucks if you don’t know that your system does them and got me into very deep sh!@$&. After working with the system for about 3 months and really enjoying it, I noticed my root partition filling up. I thought it normal, since I kept adding some software, but once Gnome keeps telling you that there is less than 1 GB left in “/” you try to do something. Luckily the pop-up with the warning also offers an inspection of the file system which showed that “/usr” was using over 8 GB of disk space. Hmm, ok – well that’s where the software lives… But why on earth is the next largest directory “/usr/share” with only 3 GB of disk usage? Where are those other 5 GB?!? First thought: Well, btrfs does inodes differently, since they are actually part of the normal file system and not set aside like in other file systems. A “df -i” actually looks like this:

juckel@denkbrett:~> df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
rootfs 0 0 0 - /
devtmpfs 1012789 515 1012274 1% /dev
tmpfs 1014799 18 1014781 1% /dev/shm
tmpfs 1014799 507 1014292 1% /run
/dev/sda3 0 0 0 - /
tmpfs 1014799 12 1014787 1% /sys/fs/cgroup
tmpfs 1014799 1 1014798 1% /media
tmpfs 1014799 507 1014292 1% /var/lock
tmpfs 1014799 507 1014292 1% /var/run
/dev/sda1 38000 43 37957 1% /boot
/dev/sda4 0 0 0 - /home

But then again, 5 GB is a LOT of blocks that are used for metadata… But the whole thing was still working, and I did not have time to worry about it, until I was actually pushed into it yesterday. The whole session froze and only a very hard reboot was possible. After this one it took forever to boot and once the X-login appears the keyboard is not working. Well, a mouse is nice and a on-screen keyboard would also do the trick, but then again, no thanks. I tried to power the whole thing off, and there was my new friend for the next hour: “No space left on device”. In this case “Could not load xklavier keyboard support: No space left on device” – well that at least explains my inability to type. I need to fix this NOW! Let’s add a “1″ to the grub command line to get into rescue mode. Shit is really piling up, when your runlevel 1 refuses to boot because “Cannot insmod XYZ: No space left on device”. Luckily, the second try got me a shell and I tried to get some breathing room to fix my system.

No space left on device – What’s really happening

This is where things got even more interesting. “df -h” said that I had about 350 MB left on “/”. So far so good, but then why does everything I try result in “no space left on device”? Weird… To top it all off, as I tried to get rid of some unpacked installation sources in “/root”, I got “cannot rm XYZ: No space left on device”. Now, come on – are you kidding me? You are supposed to delete the stuff and not add to it – somebody must be watching me right now and laughing his or her ass off. At some point I resigned and went to using the “btrfs” command which allows some modifications to the btrfs file system. It is actually an awesome tool since it allows to work with a mounted file system, but it is yet incomplete. What got me to the bottom of all this is the filesystem info of “btrfs”.

denkbrett:~ # btrfs filesystem show
...
Label: none uuid: 40507634-cb2c-4678-8b3d-d014e1b88d78
 Total devices 1 FS bytes used 20.00GB
 devid 1 size 20.00GB used 20.00GB path /dev/sda3

Hmm – somebody is not telling the truth. “df” insists that there is some space left… But since everything I see (“no space left on device”) indicates that “btrfs” is actually right and “df” might be wrong, let’s go down this path for some time. I finally am able to remove a large tar-ball lying around – that should have cleared up some room, but why is it not showing up in “btrfs filesystem show”? And wait a second, why is my home file system also showing two different numbers for usage?

denkbrett:~ # btrfs filesystem show
Label: none uuid: b3b42cba-c08e-4401-9382-6db379176a1f
 Total devices 1 FS bytes used 90.21GB
 devid 1 size 100.00GB used 85.29GB path /dev/sda4
...

This is weird. This is almost like on our large NAS for the home-directories of the ZIH users. BINGO! That NAS uses snapshots to keep old data blocks to be able to revert changes. I remember reading the article about btrfs in “c’t” (https://www.heise.de/artikel-archiv/ct/2011/23/174 and https://www.heise.de/artikel-archiv/ct/2011/24/190) – btrfs can also do snapshots. Maybe my OS is trying to be smart?! Let’s take “snapper” and see what’s there:

denkbrett:~ # snapper list
Type | # | Pre # | Date | Cleanup | Description | Userdata
-------+------+-------+--------------------------+----------+-------------------+---------
single | 0 | | | | current |
single | 1 | | Thu Nov 10 14:00:01 2011 | timeline | timeline |
single | 607 | | Thu Dec 1 00:00:01 2011 | timeline | timeline |
single | 1381 | | Sun Jan 1 00:00:01 2012 | timeline | timeline |
pre | 1609 | | Mon Jan 9 15:13:34 2012 | number | zypp(zypper) |
post | 1610 | 1609 | Mon Jan 9 15:15:48 2012 | number | |
pre | 1611 | | Mon Jan 9 15:16:35 2012 | number | zypp(zypper) |
post | 1612 | 1611 | Mon Jan 9 15:16:49 2012 | number | |
... (lots more)

Well this is nice, my OS does snapshots from time to time and before and after a system update. Actually really nice to revert to an old state if something goes wrong. But now I need to get rid of you folks. Unfortunately a “snapper delete all” is not implemented – I have to run the command for every single one of them. Are you kidding me again? Well, let’s “fake” the “all”:

denkbrett:~ # for i in `seq 1 3656`; do snapper delete $i; done

Take this! Well almost – after getting rid of about 20 snapshots I find another known friend  (https://bugzilla.novell.com/show_bug.cgi?id=733843):

kernel BUG at
/home/abuild/rpmbuild/BUILD/kernel-desktop-3.1.0/linux-3.1/fs/btrfs/inode.c:785!
invalid opcode: 0000 [#1] PREEMPT SMP

Ok – reboot, runlevel 1 again. On the second try I get rid of all snapshots and am back to 49 % file system usage!!

Lesson learned

Don’t trust “df” or “du” when using btrfs! Keep those snapshots at bay!

Aftermath

To prevent this from happening again, I tried to find out how my system is deciding to do snapshots and why to keep them. A “man snapper” reveals that the snapper configs are in “/etc/snapper/configs” and sure there is a config there for “root”. But what the heck are all those undocumented parameters?

denkbrett:~ # cat /etc/snapper/configs/root
# subvolume to snapshot
SUBVOLUME="/"
# filesystem type
FSTYPE="btrfs"
# run daily number cleanup
NUMBER_CLEANUP="yes"
# limit for number cleanup
NUMBER_MIN_AGE="1800"
NUMBER_LIMIT="100"
# create hourly snapshots
TIMELINE_CREATE="yes"
# cleanup hourly snapshots after some time
TIMELINE_CLEANUP="yes"
# limits for timeline cleanup
TIMELINE_MIN_AGE="1800"
TIMELINE_LIMIT_HOURLY="10"
TIMELINE_LIMIT_DAILY="10"
TIMELINE_LIMIT_MONTHLY="10"
TIMELINE_LIMIT_YEARLY="10"
# cleanup empty pre-post-pairs
EMPTY_PRE_POST_CLEANUP="yes"
# limits for empty pre-post-pair cleanup
EMPTY_PRE_POST_MIN_AGE="1800"

Some research on the web led me to this great article http://doc.opensuse.org/products/draft/SLES/SLES-admin_sd_draft/cha.snapper.html. I am now running with the following setup – let’s see how it goes:

denkbrett:~ # cat /etc/snapper/configs/root
# subvolume to snapshot
SUBVOLUME="/"
# filesystem type
FSTYPE="btrfs"
# run daily number cleanup
NUMBER_CLEANUP="yes"
# limit for number cleanup
NUMBER_MIN_AGE="1800"
NUMBER_LIMIT="20"    # let's only keep 20 snapshots around
# create hourly snapshots
TIMELINE_CREATE="yes"
# cleanup hourly snapshots after some time
TIMELINE_CLEANUP="yes"
# limits for timeline cleanup
TIMELINE_MIN_AGE="1800"
TIMELINE_LIMIT_HOURLY="10"
TIMELINE_LIMIT_DAILY="2"  # let's only keep daily snapshots around for two days
TIMELINE_LIMIT_MONTHLY="0" # no I don't want to have things around for 10 months
TIMELINE_LIMIT_YEARLY="0"  # or even 10 years! Who came up with those defaults?!?
# cleanup empty pre-post-pairs
EMPTY_PRE_POST_CLEANUP="yes"
# limits for empty pre-post-pair cleanup
EMPTY_PRE_POST_MIN_AGE="1800"

Currently 262 Scientists of the TU Dresden are registered, more than I expected. Registration is easy and the only information one has to store is name, email, and password; everything else can be skipped. At least some information to your interests and research are useful to gain benefit from the service It was the first time I really read through Terms and Licenses of a website and found some nice phrases I want to share. Well, everyone should read it on it’s own…

• The Provider [ResearchGate] neither previews nor automatically reviews such [stored] information (Terms and Conditions).
• Users must not publish, share, sell or make available information that is provided within the Service by the Provider or by other Users to/with any third party (Terms and Conditions).
• Unlike some other Web services, ResearchGate will definitely not store any personal data of former users (Private Policy). LOL
• Will ResearchGate sell personal data to any third parties? – No. ResearchGate will not sell or otherwise share personal data (Private Policy).

First Impression: Great! Meet you there
Link: www.researchgate.net

Sehr lesenswert und erhellend ist der Wikipedia Artikel dazu: http://de.wikipedia.org/wiki/Persipan

Demnach ist Persipan (aus Aprikose/Pfirsich steinen) ein Ersatz für Marzipan (aus Mandeln) und in der DDR gab es dann noch Resipan (Maisgrieß) und Nakapan (Kartoffelgrieß) als Ersatzstoff vom Ersatzstoff vom Ersatzstoff.

Das nenn ich mal ne Mangelwirtschaft

Der Deutsche Bundestag möge beschließen: Das Gesetz über die Ruhebezüge des Bundespräsidenten wird dahingehend präzisiert, dass ein Anspruch auf Zahlung des sog. Ehrensollds entfällt, wenn der Rücktritt eines Bundespräsidenten aus Gründen erfolgt, die in seinem privaten Verhalten liegen und/oder aus politischen Gründen, sofern diese nicht mit dem Amt des Bundespräsidenten in Zusammenhang stehen.

Die Petition ist auch intelligent formuliert, dort geht es nicht um “Rache” sonder darum eine rechtliche Grauzone zu schließen. Ich rufe hiermit alle zum Mitzeichnen auf!

https://epetitionen.bundestag.de/index.php?action=petition;sa=details;petition=22818

Tilda on Gnome 3

…and even works very well on Gnome 3

I haven’t tried it yet, but the tutorial has a gorgeous link to http://www.youtube.com/html5 where you can opt-in to view all some video in html5 format, instead of flash. You have to click on the link “Join the HTML5 Trail”, which adds an info in your youtube cookie (which is a little disadvantage, when your browser deletes all cookies after the shutdown).

Update: not all videos are available in the html5 format, but you can search for them:
“If you want to find videos with WebM formats available, you can use the Advanced Search options to look for them (or just add &webm=1 to any search URL)”

http://www.spiegel.de/politik/deutschland/0,1518,bild-314045-814010,00.html

Erinnert irgendwie an dieses Anwesen hier: http://www.youtube.com/watch?v=Ky5BC3-qwGM