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Developers’ Weblog

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How to use the subtree git merge strategy

2016-12-20 by tg@
Tags: debian grml pcli tip work

This article might be perceived as a blatant ripoff of this Linux kernel document, but, on the contrary, it’s intended as add-on, showing how to do a subtree merge (the multi-project merge strategy that’s actually doable in a heterogenous group of developers, as opposed to subprojects, which many just can’t wrap their heads around) with contemporary git (“stupid content tracker”). Furthermore, the commands are reformatted to be easier to copy/paste.

To summarise: you’re on the top level of a checkout of the project into which the “other” project (Bproject) is to be merged. We wish to merge the top level of Bproject’s “master” branch as (newly created) subdirectory “dir-B” under the current project’s top level.

	$ git remote add --no-tags -f Bproject /path/to/B/.git
	$ git merge -s ours --allow-unrelated-histories --no-commit Bproject/master
	$ git read-tree -u --prefix=dir-B/ Bproject/master
	$ git commit -m 'Merge B project as our subdirectory dir-B'

	Later updates are easy:
	$ git pull -s subtree Bproject master

(mind the trailing slash after dir-B/ on the read-tree command!)

Besides reformatting, the use of --allow-unrelated-histories recently became necessary. --no-tags is also usually what you want, because tags are not namespaced like branches.

Another command you might find relevant is how to clean up orphaned remote branches:

	$ for x in $(git remote); do git remote prune "$x"; done

This command locally deletes all remote branches (those named “origin/foo”) that have been deleted on the remote side.

Update: Natureshadow wishes you to know that there is such a command as git subtree which can do similar things to the subtree merge strategy explained above, and several more related things. It does, however, need the præfix on every subsequent pull.

“I don’t like computers”

2016-11-13 by tg@
Tags: debian pcli personal rant tip

cnuke@ spotted something on the internet, and shared. Do read this, including the comments. It’s so true. (My car is 30 years old, I use computers mostly for sirc, lynx and ssh, and I especially do not buy any product that needs to be “online” to work.)

Nice parts of the internet, to offset this, though, do exist. IRC as a way of cheap (affordable), mostly reliant, communication that’s easy enough to do with TELNET.EXE if necessary. Fanfiction; easy proliferation of people’s art (literature, in this case). Fast access to documentation and source code; OpenBSD’s AnonCVS was a first, nowadays almost everything (not Tom Dickey’s projects (lynx, ncurses, xterm, cdk, …), nor GNU bash, though) is on a public version control system repository. (Now people need to learn to not rewrite history, just commit whatever shit they do, to record thought process, not produce the perfect-looking patch.) Livestreams too, I guess, but ever since live365.com went dead due to a USA law change on 2016-01-02, it got bad.

Please save GMane!

2016-07-28 by tg@
Tags: debian news pcli rant

GMane has been down for a day or two, and flakey for a day before that. MidnightBSD’s laffer1 just linked the reason, which made me cry out loud.

GMane is really great, and I rely on the NNTP interface a lot, both posting and especially reading — it gives me the ability to download messages from mailing lists I don’t receive in order to be able to compose replies with (mostly) correct References and In-Reply-To headers. Its web interface, especially the article permalinks, are also extremely helpful.

This is a request for a petition to save GMane. Please, someone, do something! Thanks in advance!

httpd CVE-2016-5387 “httpoxy” fixed

2016-07-28 by tg@
Tags: security

A small patch was applied to httpd(8) to not pass the HTTP Proxy header as HTTP_PROXY environment variable to CGI scripts, because those often call utilities such as ftp(1), lynx(1), GNU wget, etc. which may accept this as an alternative spelling of http_proxy which is used to set a proxy for outgoing connections — something e.g. the CGI scripts in MirKarte do.

PSA: when upgrading to snapshots, boot into new kernel first

2016-03-06 by tg@
Tags: news plan snapshot tip

I’ll have to add O_DIRECTORY support to open(2) for more security in cpio(1), pax(1), and tar(1). (Maybe I’ll also add O_CLOEXEC while there…) Today’s paxmirabilis will however pick this up as soon as it’s there and thus fail if it is not supported by the running kernel yet.

Morale: when upgrading to a snapshot take care of the kernel first (install and reboot), userspace second.

To be clear: this will affect the first -current snapshot to be published after today on /MirOS/current.

mksh R52c, paxmirabilis 20160306 released; PA4 paper size PDF manpages

2016-03-06 by tg@
Tags: bug debian mksh news pcli security

The MirBSD Korn Shell R52c was published today as bugfix-accumulating release of low upto medium importance. Thanks to everyone who helped squashing all those bugs; this includes our bug reporters who always include reproducer testcases; you’re wonderful!

MirCPIO was also resynchronised from OpenBSD, to address the CVE-2015-{1193,1194} test cases, after a downstream (wow there are so many?) reminded us of it; thanks!
This is mostly to prevent extracting ../foo — either directly or from a symlink(7) — from actually ending up being placed in the parent directory. As such the severity is medium-high. And it has a page now — initially just a landing page / stub; will be fleshed out later.

Uploads for both should make their way into Debian very soon (these are the packages mksh and pax). Uploading backports for mksh (jessie and wheezy-sloppy) have been requested by several users, but none of the four(?) DDs asked about sponsoring them even answered at all, and the regular (current) sponsors don’t have experience with bpo, so… SOL ☹

I’ve also tweaked a bug in sed(1), in MirBSD. Unfortunately, this means it now comes with the GNUism -i too: don’t use it, use ed(1) (much nicer anyway) or perlrun(1) -p/-n…

Finally, our PDF manpages now use the PA4 paper size instead of DIN ISO A4, meaning they can be printed without cropping or scaling on both A4 and US-american “letter” paper. And a Бодун from the last announcement: we now use Gentium and Inconsolata as body text and monospace fonts, respectively. (And à propos, the website ought to be more legible due to text justification and better line spacing now.) I managed to hack this up in GNU groff and Ghostscript, thankfully. (LaTeX too) Currently there are PDF manpages for joe (jupp), mksh, and cpio/pax/tar.

And we had Grünkohl today!

Also, new console-setup package in the “WTF” APT repository since upstream managed to do actual work on it (even fixed some bugs). Read its feed if interested, as its news will not be repeated here usually. (That means, subscribe as there won’t be many future reminders in this place.)

The netboot.me service appears to be gone. I’ll not remove our images, but if someone knows what became of it drop us a message (IRC or mailing list will work just fine).

PS: This was originally written on 20160304 but opax refused to be merged in time… Happy Birthday, gecko2! In the meantime, the Street Food festival weekend provided wonderful food at BaseCamp, and headache prevented this from being finished on the fifth.

Update 06.03.2016: The pax changes were too intrusive, so I decided to only backport the fixes OpenBSD did (both those they mentioned and those silently included), well, the applicable parts of them, anyway, instead. There will be a MirCPIO release completely rebased later after all changes are merged and, more importantly, tested. Another release although not set for immediate future should bring a more sensible (and mksh-like) buildsystem for improved portability (and thus some more changes we had to exclude at first).

I’ve also cloned the halfwidth part of the FixedMisc [MirOS] font as FixedMiscHW for use with Qt5 applications, xfonts-base in the “WTF” APT repo. (Debian #809979)

tl;dr: mksh R52c (bugfix-only, low-medium); mircpio 20160306 (security backport; high) with future complete rebase (medium) upstream and in Debian. No mksh backports due to lacking a bpo capable sponsor. New console-setup in “WTF” APT repo, and mksh there as usual. xfonts-base too. netboot.me gone?

The things you find in upstream code…

2016-02-13 by tg@
Tags: archaeology bug pcli rant security snapshot

I had just gotten an eMail from the nightly /etc/security cronjob that the mailbox from the user foo.lock belongs to the user foo (name changed to protect the… innocent? well, I know that guy from #OpenBSD on IRC, so… YMMV… anyway). Of course, I wanted to change that to exclude mbox lockfiles…

	# Mailboxes should be owned by user and unreadable.
	ls -l /var/mail | sed 1d | \
	awk '$3 != $9 \
		{ print "user " $9 " mailbox is owned by " $3 }

… oh wow. Needless to say I fixed that, although you must update your stat(1) first; it now has a possibility to generate NUL-terminated output (or any separator, really) which I used for this. (And no, Schily, I’m still of the opinion that NUL termination, even when one has to add it to each utility separately, is the better way to go.)

Dear OpenBSD developers, repeat after me:
Do n̲o̲t̲ parse ls(1) output!
Or write 100 lines of it, or something, until it sinks in.

(It can take some writing for it to sink in… just yesternight the fanfiction I was reading was at the point where Dolores Umbridge uses her Blood Quill on the students. Coincidence.)

PDF manpages look better than before

2016-02-10 by tg@
Tags: mksh pcli

Our PDF manpages will, starting from now, be generated with Inconsolata instead of Bitstream Vera Mono as monospace font. The body font is still Gentium, of course.

To be more exact: the Teχ flavour of Inconsolata Regular and Bold, with the varl and varqu flags, is used, and because GNU groff also requires an Italic or at least Oblique font (also in its bold variant, which the mksh(1) manpage doesn’t use though), Inconsolata LGC (both Italic and Bold Italic) are plugged in there. I added them as PFA Type 1 fonts to GNU groff, so I had to make some fixes in FontForge (merging the variants into the main font, removing unused glyphs (not for LGC), fixing the validation (mostly, and not so much for LGC), autohinting where FontForge expressed a need for that, renaming glyphs to the names expected by afmtodit, …), but it works.

I’m not regenerating older PDF manpages though.

Inconsolata is also not all I wish for a monospaced font (and even bsiegert@ says nothing goes over FixedMisc) but it has, at least, a 0 (digit zero) with a correct stroke through it ☺

expect turmoil

2016-02-08 by tg@
Tags: archaeology bug hardware news pcli personal plan rant

My network at home is unstable. NetCologne suggests to switch to fibre network, but that only comes with a dynamic IPv6 address and NAT64; completely unsuitable to running a server. (I could arguably tunnel a static IPv4 address from a dedicated server to home, but that would completely foil my plans for redundancy.) So I may need an ISP (phone isn’t important) that provides me with connectivity where a static IPv4 (and, ideally, a static IPv6 /64 or /48 — but only if the reverse DNS gets delegated to me, otherwise that’s unusable) ends up at a device of my choosing (and not a plastic router which can then “forward ports”; I require full internet to end up at my own device).

HostEurope is relocating the other server, both physically and network-wise. Their plan seems fool-proof so far, though.

gecko2@ is decommissioning the server on which eurynome is hosted, shortly. This will also be no small amount of fun for everyone involved. Expect old links, SSH host keys, etc. to break. This explicitly includes /etc/ssh/*known_hosts.

During all those moves, I will downsize my DNS zones and change some entries, so that old or duplicate records will be gone.

I’ll likely generate and publish completely new hostkeys (both gzsig(1) and PGP clearsigned) once this is all over. The current gzsig(1) key is at the end of /usr/share/doc/README in any installed system. (Do note MD5 is considered insecure.) My current PGP key is 9031955E7A97A4FDA32B2B8676B534B2E99007E0 but this requires GnuPG, so check both.

My seeming inability to remember rarely-used “secure” passwords, i.e. those not fitting into my normal schemata, led to me not attempting to run a CA myself any more. While, thanks to rsc, we have an official certificate for www.mirbsd.org now, I probably will get StartSSL for “all” other systems (i.e. herc, as I appear to be downsizing), despite it lacking the SSL client purpose (important e.g. to SMTP). This shouldn’t affect anyone.

PS: I still hate Karneval!

FOSDEM

2016-01-28 by tg@
Tags: event

Of course, some MirBSD presence will be at FOSDEM this year. There’s no FOSDEM without mirabilos, after all.

We have no booth nor any other set place, and no planned talk schedule either, so coordination of meetups will be tricky. I’ll try to get into IRC at least occasionally, but WLAN is usually shitty.

hardware problems on www.mirbsd.org solved (thanks HE) + snapshot

2016-01-20 by tg@
Tags: bug hardware news snapshot

Fearing loss of the server or the hard disc when reporting the hard disc issue I postponed that and created a snapshot (for i386) and a CVS repository snapshot and uploaded them first then backed up everything worthwhile on fish and created myself some custom rescue media.

(Some background info — this server is from 2006, and back then, they usually cost around 100 €, while this is partially sponsored. I was fearing stopping of the sponsoring or shutdown of such an old real iron hardware even though it works fine for my needs.)

Then I shut the server down and asked HostEurope support to check the HDD and, if possible, when replacing, put the old HDD into the second slot (I checked, the PowerEdge 750 has two of them). With a big German dedicated hoster that shall stay unnamed (it’s not the Uffline one), even with a RAID 1 you’re SOL because they refuse to just swap the discs, but I decided to try anyway.

So I put the request up in KIS and thought they’d do it during normal working hours (as off-hour work costs extra), but no more than four hours later, the HDD was checked as faulty, a new one (even bigger as they don’t stock 80 GB ones any more ☺) was put into the first slot and the old one into the second slot, and… oh well. The machine was booted into BIOS Setup, and I may connect with the DRAC III/XT (which needs a Java 1.4 plugin for MSIE, or telnet (not ssh), and whose password I forget due to unuse).

Some tricking around later I found out that their new netbootable rescue system (a Grml 2014.03 PONY WAGON) doesn’t work with my server, so I resigned to pay the 25 € to have someone boot it up with a Knoppix CD (uh-oh). After all, I just needed any system with which I could dd(1) the custom MirBSD installer ISO I previously made onto /dev/sda then boot into it.

To my surprise, I got an eMail telling me they had booted it with a Grml (not from network) and set it up so I could ssh(1) in… with the “initial password”. One eMail later I found out that this server predates passwords in KIS, and by now I’m in the process of restoring services by copying everything from the old to the new disc (only lost some directories under the anoncvs mirror from ocvs which is easily rsync’d right later)… ah, this completed during writing of this wlog/news entry.

In the end, this all worked perfectly fine, and I’ll be pointing the www RR back to fish after the bad disc was removed and everything has rsync’d back to my satisfaction.

CVE-2016-0777 OpenSSH roaming leak

2016-01-14 by tg@
Tags: bug security snapshot

While our OpenSSH has (now: had) some code related to roaming, I believe our version not affected. If desired, CVS HEAD ships with the entire code removed.

I fixed lots of mksh bugs today!

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