korki’s corner

Yesterday I had to rearrange my data over my hard disks and since zfs [2][3] is not yet 100% efficient in linux distros[4] I have to do all the dirty work manually…

My first question is how the hell does the stupid fstab accept the bind option. Since its man page says as much as nothing [5]

The quick and dirty way into finding out how the stupid fstab syntax works is to mount a filesystem normally as you would do via the mount command (bind,loop anything!!!) and then check the /etc/mtab file to understand the syntax! its freaking cool and easy then to copy paste the mtab directives into the fstab file and voila! no fstab related reading is necessary!

for instance or if you prefer it as an example after some mount deeds the system reports the following on the mtab


msi939 ~ # cat /etc/mtab
...
/dev/hdb1 /mnt/hdb1 reiserfs rw 0 0
/dev/sda1 /mnt/sda1 reiserfs rw,noatime 0 0
/dev/sdc1 /mnt/sdc1 ntfs rw,noatime 0 0
/dev/sdd1 /mnt/sdd1 ext3 rw,noatime 0 0
/mnt/hdb1/mirror /home/mirror none rw,bind 0 0


which in turns translates (after using UUIDs) to the following fstab:


UUID="064368f6-a696-44b3-8a84-31e47c16d7cb" none swap sw 0 0
UUID="cb0b34366-9f99-4394-8c0d-aaa9e3c7503c" /mnt/hdb1 reiserfs noatime 0 0
UUID="4aa2348-bc8a-437d-8d72-59c6c364e0b4" /mnt/sda1 reiserfs noatime 0 0
UUID="6AE34GFCE42BC8E1" /mnt/sdc1 ntfs rw,noatime 0 0
UUID="ac7asd3d-69a6-424c-bd3c-fb0ae35a813e" /mnt/sdd1 ext3 noatime 0 0
/mnt/hdb1/mirror /home/mirror none bind,defaults 0 0


(if by accident it happens of your UUIDs matching one of the above don’t worry, it ain’t a bug! I simple changed a bit the UUIDs with random keystrokes - If you do have a match, bear in mind that this is something really rare, so send me a mail, maybe we are meant to get acquainted :))

I hope you enjoy this fragment of knowledge, a simple thank you is sufficient

This is a quicky one, due to lack of time.

I tried for the past 24h to install eclipse + pdt on a couple of gentoo boxes I operate for home use. I could describe myself  at least as “experienced user“, and yet I couldn’t make it happen the right gentoo way [*]. After spending about 4-5 hours guessing what kind of dependencies should be sufficient to satisfy in order to eventually install the pdt, since the update manager of eclipse [3.2] provided by gentoo stable is a bit old and could not pick them automatically.

Well dudes if you are here in order to install eclipse and pdt on a gentoo system skip the stupid eclipse ebuilds (totally unmaintained maybe?) and go grab eclipse from the source: >>>>> READ HERE AND FOLLOW THE INSTRUCTIONS. IT DEFINATELY WORKS!!!! <<<<<.

Yeah I ebuilded the eclipse from the sources (20 mins - no ccache no distcc, it is java dude ) in order to have an (obsolete) cvs browser and a C dev platform…. Yeah right…

Conclusion gentoo + eclipse ebuild = bad idea… Do it the Clint Eastwood way: download unpack use…

*The right gentoo way implies the respect to ebuilds and follow the exact instuctions from the official sources/package maintainers etc…

One of the problems I had recently on a x86_64 gentoo installation with an ati 1550 graphics adapter was the constant Xorg-server crashing with the following message;

Fatal server error:
Caught signal 11. Server aborting

That message was haunting the damned Xserver and strangely enough, I had never seen it in my linux quest through the years. When the X couldn’t load it never segfaulted. During my courses at ceid and the C language classes [1][2] [and others], I had the strong belief that a segfault (signal 11) occurs only due to a PEBKAC. Namely from poor programming practice or from incorrect linking.
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It was sometime since I returned from vocation and I hadn’t use the gen64 system for a demanding task. Recently I had to do some simulations with ns2 and the performance was really poor! Meaning that some simple scenarios that demanded about 30 seconds (on the same system) required about 6-7minutes to complete. This utterly irritating behavior was most unexpected so actions should be taken to revert it.

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Hi all,

this is supposed to be some kind of tutorial series that tries to focus into the only disadvantage that gentoo has. The wasted cpu cycles due to constant compiling. And constant compiling means less productivity and of course more energy consumption. The last one is quite critical now days for home users or for operators owning a dedicated server in a datacenter with some power management rules.

The solutions for these so far that I have thought of are two (if you have something else on your mind please be my guest and comment in order to add it in the series)

1. ccache
2. distcc
3. combination of the above

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After summer vacations I decided it was high time to freshen up the gentoo systems (all of them are x86_64 arch - remind me one day to write some about the home network ). Well after some 200+ packages marked for build I sat back and continued with my writing assignment…

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Προσωρινά τα gentoo-aware services (gentoo rsync and http ftp distribution files) θα είναι down.

Η επαναλειτουργία αναμένεται να συμβεί το αργότερο την Δευτέρα (9/6/2008) το πρωί. Ωστόσο υπάρχει αρκετά μεγάλη πιθανότητα να μην εξαντληθεί αυτό το χρονικό διάστημα και να γυρίσουν πάλι οι υπηρεσίες online σήμερα το βράδυ (το νωρίτερο). Σε κάθε περίπτωση θα ενημερωνεται το παρόν για κάθε εξέλιξη (σαν comment (σχόλιο)).

Συγνώμη εκ των προτέρων για την όποια αναστάτωση προκαλεί η αναβάθμιση.

First of all; DO NOT PANIC.

Of course what you did is terribly stupid but it is fixable. Some history (if you are in panic jump to the next paragraph. If you are not sit back kick off your shoes and enjoy the melodies (c) offspring ). What you did is terribly stupid because python is the heart of gentoo package manager (yeah I know who could think of choosing python for such a critical task but hey! someone did). The python is long gone and with it the whole package management. No more emerge or maybe not? Take a look at how the packages builders are designed for gentoo and then you might have understood what your mistake was. And I insist pointing that out.

Well some quick words of advice for the faint in heart in a step by step basis;

1. Download a gentoo python distribution eg Python 2.4.4. You download it with #wget ftp://ftp.ntua.gr/pub/linux/gentoo/distfiles/Python-2.4.4.tar.bz2
2. Unbzip it with #tar jxvf Python-2.4.4.tar.bz2
3. Enter the flattened directory; #cd Python-2.4.4
4. Configure the Python distribution with : # ./configure –with-fpectl –infodir=/usr/share/info/ –mandir=/usr/share/man
5. build the distribution with # make
6. and then install it to the system with: # make install prefix=/usr
7. now if you are lucky the emerge should work: # emerge python

If the above step by step tutorial works you have to consider yourself VERY lucky. If it doesn’t try w-getting another Python version and cross your fingers. If you like me thinking of trying the above for educational purposes (gentoo without python at all) ONLY then I have to say that this is NOT a good idea. In fact it is a terrible moronic idea and yours, mine and everyone’s picture that even thinks about it should be in the vocabulary next to the word STUPID, even if that person did it just to check out a gentoo without python!

On of the great deals on sourceforge is its capabilities. It provides to the opensource developer 100mbyte of web space and unlimited cvs and file release data storage. It is simply an unbeatable offer. Of course you have to create opensource project in order to use its services.

I am working with sf for the wifiadmin project a project that some farseeing members of my wifi community started long ago. Wifiadmin is an open source GPLed piece of software that allows its user to do basic configuration to its interfaces. My vision is to integrate it with the pfsense another great piece of work based on FreeBSD as a wifi router. Before integrating these applications much development has to be done, and in source forge is being done with cvs (or svn) but in this article I will cover cvs. I gained much experience while contributing to an opensource project so it is quite an event and I insist that everyone should involve with something they like and give back some work hours to the community to help out everyone.

Enough with mumbling, lets get to business (note that we are referring to project wifiadmin. Replace it with the suitable project name that you are dealing with!)

In order to checkout the cvs sf tree the following operations are needed in your working console;

1. export CVSROOT=:ext:user@wifiadmin.cvs.sourceforge.net:/cvsroot/wifiadmin
2. export CVS_RSH=ssh
3. ssh user@wifiadmin.cvs.sourceforge.net

• login with your password
• The cvs.sf server after your login should kick you out immediatly

1. cvs -z3 -d:ext:ssh:user@wifiadmin.cvs.sourceforge.net:/cvsroot/wifiadmin co -P wifiadmin

Explanation of the steps; 1-2 steps make your life easier by using the env variables in order to type less the cvs commands. With 2 a simple cvs commit (instead of a cvs blablabla commit) should be sufficient later! With step number 3 you get the latest version as a local copy. STEPS 1-3 are one timers. Never do them again (except if you are interested in downloading again the cvs tree). We login @ cvs.sf server in order to create some important account files in order to be able to use our shell. Also one intresting part of the process is the ssh key authentication (to avoid the necessity to use passwords @ ssh) you can create an ssh key following these simple steps;

1. First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:
2. a@A:~> ssh-keygen -t rsa
   1. Generating public/private rsa key pair.
   2. Enter file in which to save the key (/home/a/.ssh/id_rsa):
   3. Created directory ‘/home/a/.ssh’.
   4. Enter passphrase (empty for no passphrase):
   5. Enter same passphrase again:
   6. Your identification has been saved in /home/a/.ssh/id_rsa.
   7. Your public key has been saved in /home/a/.ssh/id_rsa.pub.
   8. The key fingerprint is:
      1. 3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A
3. Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):
4. a@A:~> ssh b@B mkdir -p .ssh
5. b@B’s password:
6. Finally append a’s new public key to b@B:.ssh/authorized_keys and enter b’s password one last time:
7. a@A:~> cat .ssh/id_rsa.pub | ssh b@B ‘cat >> .ssh/authorized_keys’
8. b@B’s password:
9. From now on you can log into B as b from A as a without password:
10. a@A:~> ssh b@B hostname

Edit the code at your files the submit the edited one with the call; cvs submit -m “blabla” where blabla denotes the reason for your actions (you may not use -m switch but things will roll smoother if you indicate with a simple comment why you did what!)

In order to remove an existing file you should do a cvs rm relative_path_from_cvs_root/filename and then do a cvs commit

In order to add a new file you can do a cvs add relative_path_from_cvs_root/filename and then do a cvs commit

In order to check if there are updates you have to do a cvs update

Hope it helps!

Ο κόμβος pwmn.net-kOlga προσφέρει σε φίλους/φίλες που επιθυμούν να συνδεθούν προσωρινά, στον κορμό του PWMN μέσω internet την δυνατότητα να χρησιμοποιήσουν την υπηρεσία του VPN (PPTP)που προσφέρει ο κόμβος. Η κάθε σύνδεση λαμβάνει dedicated 256kbps upload 128 kbps download (το bandwidth αυτό δίδεται από την dsl που εξυπηρετεί το σπίτι). Η ταχύτητα διασύνδεσης με τον κορμό του PWMN ανέρχεται στα 4 MByte/s οπότε το bottleneck που υπάρχει περίπτωση να αντιμέτωπίσετε θα οφείλεται αποκλειστικά στην dsl. Για πληροφορίες και για account παρακαλώ επικοινωνήστε μέσω του forum με προσωπικό μήνυμα.

Η σύνδεση γίνεται στο address korki.pwmn.net και τα user credential δίδονται από το forum. Κατά την λειτουργία κανείς περιορισμός δεν υφίσταται, ως προς το είδος της κίνησης που επιθυμεί να περάσει ο πελάτης [1] . Οι αποδιδόμενες διευθύνσεις από για το VPN είναι στο range 10.140.4.240/28. Επίσης προαιρετικά και μετά από συνεννόηση εκτός από συνδέσεις τύπου PPTP μπορεί να δίδονται συνδέσεις τύπου OpenVPN και IPsec (tunneled).

Στις ρυθμίσεις για το PPTP πρέπει υποχρεωτικά να είναι ενεργοποιημένη η επιλογή για 128bit encryption.

Another happy service by pwmn.net-kOlga.

[1] Προσοχή: όλη η κίνηση περνάει μέσα από το snort οπότε ύποπτες δραστηριότητες -όπως μπορεί να της θεωρήσει ή εφαρμογή- μπορεί να διακοπούν κατά το δοκούν του IDS.