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MirWarm

07.07.2013 by tg@
Tags: debian fun

zz̼̐z

Time for more neighbours’ cat posts, apparently. It’s warm, so the cat’s sleeping outside. Not disturbed by much.

Me envious. Too warm to go to the ice salon (bike’s in repair, car’s hot enough to boil eggs on it, public transport not better).

virsh send-key guestname KEY_LEFTALT KEY_SYSRQ KEY_H

This doesn’t work in virt-manager, but the virsh CLI tool is just fine.

PS: zerofree rocks! And can be installed in Grml 2011.05 just finely.

Okay, so imagine this: you just generated an SSH RSA key and threw its public part on system B into ~foo/.ssh/authorized_keys and its private part on system A into ~bar/.ssh/id_rsa but can’t login. Why?

Automated processes (Jenkins *cough*) often need you to ssh(1) manually once, to accept the remote host’s server key. Do that.

The id_rsa file on system A must be owned by the user bar and chmod 0600 or 0400 (similarily, the .ssh directory has strict permission checks, and everything in the path until there). Check those.

And, the most surprising one of the day: if there’s an id_rsa.pub it will be used for offering a key to the remote host (B) even if it does not match the secret key. Deleting A:~bar/.ssh/id_rsa.pub apparently makes OpenSSH generate the public part from the secret key each time (or just put the correct pubkey there), but if one’s there, it seems to like to use them. (That was the only part of this post that was news to even me, of course ☺)

And, as bottom line: hello to Planet Debian from “mirabilos at work”, too. I’ll occasionally tag posts so they show up here, if I think they’re of interest, since I’m doing Debian work at the dayjob, too.

Waypoint Statistics

08.06.2013 by tg@

mirabilos’ found waypoints

I’ve finally gotten around to listing all Waypoints (Geocaches, Opencaches, Closedcaches, Earthcaches, Terracaches including Locationless, Navicaches, etc.) I’ve found a box, enjoyful, educating, a good place to hide one myself, etc. and putting up a list and, of course, generate my own statpic.

I’ll put them up for the other project members, too (already made a picture for gecko2@ but bsiegert@ still needs one; we also need to collect offline lists of found, owned and attended waypoints)…

A bit of background story: I decided, years ago, to have an offline list of cache finds in case something would happen. Just, I had found way too many already, so this was a huge bit of work. Oh well… I of course procrastinated, and then something did happen (Opencaching wanting to force a Restricted Commons licence; me disagreeing and suggesting a change; some trigger-happy person immediately deleting my account without waiting for the discussion or the decision period to end; weeks of forum discussions; Opencaching allowing dual-licencing; them telling me they can’t restore my data – probably never heard of databa…sorry, MySQL backups). And I still didn’t have the list. Now I do; recreated even the OC information from what was still accessible and with help from one OC supporter (“mic@”, thanks); merged caches that are co-listed on several platforms, etc. (still need to put in the FTF/STF/TTF/4TF/LTF and voting/favourites information) and a statpic, all in Open Source and Open Data, in cvs(1) with mksh(1) and… a… frontend for libgd2 I admit, but we had been using that for the MirWebsite for a while already.

I suggest every geocacher keep an offline or local record of all their finds (and hides and attended logs) for things like this, in case some platform decides to… let’s say, “put your data into the cloud… where it is? I don’t know”.

DynDNS

20.05.2013 by tg@
Tags: archaeology debian

Apparently (hi Zhenech, found on Plänet Debian), a Man does not only need to fork a child, plant a tree, etc. in their life but also write a DynDNS service. Perfect for opening a new tag in the wlog called archæology (pagetable.com – Some Assembly Required is also a nice example for these).

Once upon a time, I used SixXS’ heartbeat protocol client for updating the Legacy IP (known as “IPv4” earlier) endpoint address of my tunnel at home (My ISP offers static v4 for some payment now, luckily). Their client sucked, so I wrote on in ksh, naturally.

And because mksh(1) is such nice a language to program in (although, I only really begun becoming proficient in Korn Shell in 2005-2006 or so, thus please take those scripts with a grain of salt, I’d do them much differently nowadays) I also wrote a heartbeat server implementation. In Shell.

The heartbeat server supports different backends (per client), and to date I’ve run backends providing DynDNS (automatically disabling the RR if the client goes offline), an IP (IPv6) tunnel of my own (basically the same setup SixXS has, without knowing theirs), rdate(8) based time offset monitoring for ntpd(8), and an eMail forwarding service (as one must not run an MTA on dynamic IP) with it; some of these even in parallel.

Not all of it is documented, but I’ve written up most things in CVS. There also were some issues (mostly to do with killing sleep(1)ing subprocesses not working right), so it occasionally hung, but very rarely. Running it under the supervise of DJB dæmontools was nice, as I was already using djbdns, since I do not understand the BIND zone file format and do not consider MySQL a database (and did not even like databases at all, back then). For DynDNS, the heartbeat server’s backend simply updated the zone file (by either adding or updating or deleting the line for the client) then running tinydns-data, then rsync’ing it to the djbdns server primary and secondaries, then running zonenotify so the BIND secondaries get a NOTIFY to update their zones (so I never had to bother much with the SOA values, only allow AXFR). That’s a really KISS setup ☺

Anyway. This is archæology. The scripts are there, feel free to use them, hack on them, take them as examples… even submit back patches if you want. I’ll even answer questions, to some degree, in IRC. But that’s it. I urge people to go use a decent ISP, even if the bandwidth is smaller. To paraphrase a coworker after he cancelled his cable based internet access (I think at Un*tym*dia) before the 2-week trial period was even over: rather have slow but reliable internet at Netc*logne than “that”. People, vote with your purse!

mksh R45 released

26.04.2013 by tg@

The MirBSD Korn Shell R45 has been released today, and R44 has been named the new stable/bugfix-only series. (That’s version 45.1, not 0.45, dear Homebrew/MacOSX packagers.)

Packagers rejoice: the -DMKSH_GCC55009 dance is no longer needed, and even the run-time check for integer division is gone. Why? Because I realised one cannot use signed integers in C, at all, and rewrote the mksh(1) arithmetics code to use unsigned integers only. Special thanks to the people from musl libc and, to some lesser amount, Natureshadow for providing me with ideas what algorithms to replace some functionality with (signed shell arithmetic is, of course, still usable, it is just emulated using unsigned C integers now).

The following entertainment…

	tg@blau:~ $ echo foo >/bar\ baz
	/bin/mksh: can't create /bar baz: Permission denied
	1|tg@blau:~ $ doch
	tg@blau:~ $ cat /bar\ baz
	foo
 

… was provided by Tonnerre Lombard; like Swedish, German has got a number of words that cannot be expressed in English so I feel not up to the task of explaining this to people who don’t know the German word “doch”, just rest assured it calls the last input line (be careful, this is literally a line, so don’t use backslash-newline sequences) using sudo(8).

Since a while…

I am a proud
EarthCache Master

On the other hand… I should probably put up my own, local, list of found caches, considering what happened to me on “Open”caching. And maybe write intros for people new to geocaching, since it’d be virtually no work now had I done it initially. (And for fanfiction readers! I wish I’d kept a list of read fics, not just of these I currently read and/or are currently unfinished.)

GNU autotools generated files

20.02.2013 by tg@
Tags: debian rant

On Planet Debian, Vincent Bernat wrote:

The drawback of this approach is that if you rebuild configure from the released tarball, you don’t have the git tree and the version will be a date. Just don’t do that.

Excuse me‽

This is totally inacceptable. Regenerating files like aclocal.m4 and Makefile.in (for automake), configure (for autoconf), and the likes is one of the absolute duties of a software package. Things will break sooner or later if people do not do that. Additionally, generated files must be remakable from the distfile, so do not break this!

May I suggest, constructively, an alternative? (People – rightfully, I must admit – complain I’m “just” ranting too much.)
When making a release from git, write the “git describe” output into a file. Then, use that file instead of trying to run the git executable if .git/. is not a directory (“test -d .git/.”). Do not call git, because, in packages, it’s either not installed or/and also undesired.

Couldn’t comment on your blog, but felt strongly enough about this I took the effort of writing a full post of my own.

(But thanks for the book recommendation.)

git log -n 1 --all --full-history --pretty=format:'%cD'

This should™ scan all branches, take the chronologically last commit and output its committer date. Still doesn’t take into account git-receive-pack times, but we can just look at the mtime of the projectname-commits@lists.forgename mailing list for that.

PSA: Referring to Unicode codepoints.

If your Unicode codepoint is, numerically, between 0 and 65533, inclusive, convert it to hexadecimal and zero-pad it to four nibbles. For example, the Euro sign € is Unicode codepoint #8364 which is 20AC hex; the Eszett ß is 223 which is DF hex, padded 00DF.
Then write an uppercase ‘U’, a plus sign ‘+’, and the four nibbles: U+20AC U+00DF
In mksh, JSON, etc. it’s a backslash ‘\’, a lower-case ‘u’ and four nibbles.

Otherwise, your Unicode codepoint will be, numerically, between 65536 and 1114111, inclusive, that is hex 10000 to 10FFFF. (There’s nothing on 65534 and 65535, nor above these figures.) In this case, convert it to hex, zero-pad it to eight nibbles and write it as an uppercase ‘U’, a hyphen-minus ‘-’ and the eight nibbles. In C-like escapes for environments supporting the Unicode SMP, that’s a backslash ‘\’, an upper-case ‘U’ and eight nibbles. Do not, in either case, use less (or more) hex digits than specified here. For example, there’s a famous Unicode codepoint U-0001F4A9 “PILE OF POO”. That’s not the same as U+1F4A9. The latter reads as U+1F4A “GREEK CAPITAL LETTER OMICRON WITH PSILI AND VARIA” and a digit 9 (Ὂ9). Be educated.

Since this wlog runs on MirBSD, which limits itself to the Unicode BMP voluntarily, and as nōn-BMP is not widespread anyway, I cannot reproduce the “PILE OF POO” here, but you can just duckduckgo it.

Let’s start a convention: bare-metal machines have the linguistic male gender („der Computer“, he needs to be rebooted), whereas VMs have the linguistic female gender („die virtuelle Maschine“, she runs better since the last upgrade of Linux-KVM), and neutral linguistic gender is used when you cannot or do not want or need to make such distinction.
This is, of course, entirely unrelated to human gender, but not unrelated to #debian-68k (on OFTC) discussions ;-)

ObRant: DO NOT USE xz COMPRESSION LEVELS ABOVE 6! (For -7 we can make exceptions, for example in Debian *-dbg or *-source packages.) You may use -e if you absolutely need the better compression, but please think of the poor sods who have to create the archives. You must not use the highest compression levels -8 or -9 since they have absolutely insane memory requirements on compression and will still hinder machines with less RAM on decompression. (Using -e only affects CPU usage at compression time; decompression is exactly as fast and memory-consuming as without.) Furthermore, DO NOT CHOOSE A COMPRESSION LEVEL WITH A DICTIONARY SIZE MUCH LARGER THAN THE DATA TO COMPRESS, as that makes absolutely no sense and will rather worsen than improve compression. As a reminder, xz uses the following dictionary sizes:

  • 256 KiB at -0 (compresses better than gzip(1) and faster than either gzip(1) or bzip2)
  • 1 MiB at -1
  • 2 MiB at -2 (compresses better than gzip(1) and bzip2 without losing much speed)
  • 4 MiB at -3 and -4 (the difference is in the match finder between these two levels)
  • 8 MiB at -5 and -6
  • 16 MiB at -7 (186 MiB RAM used to compress a file)
  • 32 MiB at -8 (370 MiB RAM used to compress a file)
  • 64 MiB at -9 (674 MiB RAM used to compress a file)

Decompression uses less than 1 MiB more than the dictionary size, but the dictionary must always be allocated wholly. (You’re fine to use custom presets, but mind the RAM usage!) As a general rule, if you have something of up to 20 MiB to compress, -4 is fine, and -5 will only be better if you have similar data spread across the whole of the file instead of close to each other. When I make mksh distfiles, I instead put files close to each other that have related content, which improves compression much more nicely without penalising low-memory systems; for example, you could put documentation, Makefiles, scripts, m4(1) files, and C source code into groups before archiving, instead of doing it alphabetically.

Another note on bzip2: its decompression is slow. I see no reason to use it any more, at all. Use gzip(1) if you care for compatibility or have an issue with xz not having a free copyright licence, and xz otherwise.

mksh made quite some waves (machine translation of the third article) recently. Let’s state it’s not just Amigas – ara5 is a buildd running the Atari kernel, an emulated though. On the other hand, the bare-metal Ataris used to be the fastest buildds, so I expect we get them back online soonish. I’m currently fighting with some buildd software bugfixes, but once they’re in, we will make more of them. Oh, and porterboxen! Does anyone want to host a VM with a porterbox? Requirements: wheezy host system (can be emulated), 1 GiB RAM, one CPU core with about 6500 BogoMIPS or more (so the emulated system has decent speed; an AMD Phenom II X4 3.2 GHz does just fine). Oh, and mksh is ported to more and more platforms, like 386BSD 0.0 with GCC 1.39, and QNX 4 with Watcom… and more bugfixes are also being worked on. And let’s not forget features!

jupp got refreshed: it’s got a bracketed paste mode, which is even auto-enabled on xterm-xfree86 (though the xterm(1) in MirBSD’s a tad too old to know it; will update that later, just imported sendmail(8) 8.14.6 and lynx(1) 2.8.8dev.15 into base, more to come) and will be enhanced later (should disable auto-indent, wordwrap, status line updates, and possibly more), lots of new functions and bindings, now uses mkstemp(3) to create backup files race-free, and more (read the NEWS file).

In MirBSD, Benny and I just added a number of errnos, mostly for SUSv4 compliance and being able to compile more software from pkgsrc® without needing to patch. This is being tested right now (although I should probably go out and watch fireworks in less than a half-hour), together with the new imports and the bunch of small fixes we accumulate (even though most development in MirBSD is currently in mksh(1) and similar doesn’t mean that all is, or worse, we were dead, which we aren’t). I’ll publish a new snapshot some time in January. The Grml 2012.12 also contains a pretty up-to-date MirBSD, with a boot(8/i386)loader that now ignores GUID partition table entries when deciding what to use for the ‘a’ slice.

If you haven’t already done so, read Benjamin Mako Hill’s writings!

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