I made a change in the blogger configuration to ease the later work when blogging. It is possible that older entries are not correctly formatted.
Well I learned something about the GDM configuration by reading the well written gnome gdm manual. However, that did not solve my Gnome cofiguration problems.
But at least I know a little bit more how to configure the user screen and put useful on it through the use of an Xwilling script.
I must say I am currently a bit lost in the different mechanisms to start and stop services. I used to perform these tasks with the standard /etc/init.d/... scripts. But it seems that it does not work completely in this way. There seems to be now systemctl, service and chkconfig commands.
service sshd start
to start the ssh daemon.
service sshd stop
to stop the ssh daemon.
chkconfig sshd on
to enable the ssh daemon so as to start it after boot.
To use systemd, the following commands come handy:
systemctl start sshd.service
to start the ssh daemon.
systemctl stop sshd.service
to stop the ssh daemon.
systemctl enable sshd.service
to enable the ssh daemon so as to start it after boot.
I finallly reinstalled fedora. So now I have a completely new Fedora version and I am not amused. Really not amused. First I had trouble with Grub, then I had trouble with the DNS and finally I had to curse against gnome 3.0. Or is it only unity... I am not sure. I do not rant. But this time, I am more than annoyed. I would not say I am pissed off. But nearly. I keep asking myself: why? Why? Why?
First of all Grub... Actually I did not want to reinstall the boot directory from Grub. I wanted to be able to use my old fedora if I needed it. But that did not really work. So I let the new fedora (or I should say anaconda, overwrite the boot loader).
Then, for some reason the DNS was not configured and I had to reconfigure it per hand. Why ?
Finally, how is gnome 3.0 supposed to be used. Why can't I create my desktop icons ? Why can't I add launchers to the panel or the desktop. My computer is supposed to be used. I do not care really how it looks.
I bought a number of linux magazine during my week holiday and discovered a number of new interesting, useful things:
And one thing I really found useful is: commandlinefu (http://www.commandlinefu.com/). This site provides a way for people to advertise useful commandline tricks. I should probably follow them, I will learn a lot. And it already started.
I already learnt a new useful command: youtube-dl. Say you have some google URL:
http://www.youtube.com/watch?v=1504cSBhWG0And you want to get the url of the file being downloaded, then you can use (-b for best quality and -g for just getting the url): $> youtube-dl -b -g http://www.youtube.com/watch?v=1504cSBhWG0
Of course this command has a certain number of options.
I installed Fedora 11. I still need to see what the differences are and see which software I need to install this time. The advantage of only updating (which did not really work for me from version 9 to 10).
The main new things seems to be that livna has more or less been replaced by rpmfusion. So I still have to see whether I can still install all the software I need for my own pleasure.
I will probably comment in this entry.
To install linux I used the CD from PCWELT Linux 5/2009.
My computer is partitioned in the way that the /boot partition is under ext3 outside the lvm. But the '/' partition is under an lvm partition. In that way I can easily resize and create new partition. I used a new partition so that I should be able to come back to my older linux version, though I have not tested that yet.
One of the important change in fedora 11 (and perhaps fed 10) is the use of ext4.
One of my colleague is somewhat sceptical of the use of partitioning though I must say with lvm it is a real pleasure, but OMMV (our mileage may vary).
In the new version of Xorg, the default configuration does not allow you to kill the X server with the keys: Ctrl+ Alt+ Backspace. Whether I find that good or not. Well I ain't so sure.
I really like the new background for the desktop. I suppose I might keep it some time. I really like the birds. Though searching with google there seems to be a lot of cool backgrounds: e.g http://www.wallpaperlinux.com/v/Fedora/Fedora+11+Linxu+Wallpaper+Fedora+11+Desktop+Background.jpg.html
I have a small problem withe the auto mount for CDs. It does not seem to be working. I am not sure of the reason.
See: http://rpmfusion.org/Configuration/.
At least using RPM fusion I can install: mplayer and vlc. I will have to see whether I can also play wmv, mpeg and avis just as I wish. It seems to be the case.
With these things you never know. But I wonder whether I would not have rather updated the distribution instead of installing a new version. I am still not finished.
I just read the section on per CPU variables from the Linux Device Drivers book from O'Reilly (TODO link).
The use of per CPU variable helps improving performance by limiting the cache sharing between CPUs. The idea is that each CPU has his own private instance of a given variable.
A variable can be defined using the following macro: DEFINE_PER_CPU(type,name);
It is important to note that a kind of locking mechanism is still needed for the CPU variables in case:
Therefore, each instance should be updated using a simple mechanism to lock the variable during the changes. This can be done by using the get_cpu_var() and put_cpu_var() functions, for example:
get_cpu_var(variabletoupdate)++;
put_cpu_var(variabletoupdate);
It is also possible to access the variable values from other processors using: per_cpu(variable, int cpu_id); but a locking mechanism must be implemented for these cases.
Memory allocation for dynamically allocated per-CPU variables is performed using:
void *alloc_percpu(type);
void *__alloc_percpu(size_t size , size_t align);
Deallocation is achieved using: free_percpu().
Accessing a dynamically allocated per-CPU variable is performed by using
per_cpu_ptr(void * per_cpu_var, int cpu_id).It returns a pointer to the variable content. For example,
int cpu;
cpu= get_cpu();
ptr = per_cpu_ptr(per_cpu_var, cpu);
put_cpu();
Note: the use of the method to free the cpu from the lock.
In this post, I sum up the main Makefile parameters and targets, right now it mainly corresponds to $make help but I might edit this entry to add useful information.
First of all use (if in the directory of the kernel sources)
$ make helpor if you are not in the directory of the kernel sources (then located in
$ make -Chelp
This more or less gives the following information.
This outputs a list of possible target and supplementary information:
Note that there are also some little things about tags for editors, but I am not so sure what it really brings.
Yes I like standards... Standards are great... Of course you should not exaggerate it, but yeah standard base are a good thing for linux.
So take a look at the Linux Standard Base ( aka LSB). It is a specification of what rules all linux distribution should respect.
For example, it specifies the executable and linking format: ELF, as well as specifying a number of useful libraries: libc, libm, lipthread, libgcc_s, librt, libcrypt, libpam and libdl. Some util libraries are also specified: libz, libncurses, libutil.
It also specifies a number of commandline command ( see the standard on this subject)
For a few things I am interested in doing, I wanted to be able to have a small script preparing as soon as I boot up. Perhaps it is more interesting to use atd or cron for this but I wanted to make sure how the initscript system works.
So I prepare a small script in order to start some system tools as soon as the boot process is finished.
For example, a little tool starting a remote process when I first boot which would allow me to use some remote processing facilities, e.g (focused) crawler. This could be also some system starting before/after the httpd daemon is up.
For this I took a look at the /etc/init.d/postgres script.
#!/bin/sh # newscript This is the init script for starting up the newscript
# service
#
# chkconfig: - 99 99
# description: Starts and stops the newscript that handles \
# all newscript requests.
# processname: mynewscript
# pidfile: /var/run/mynewscript.pid
# Version 0.1 myname
# Added code to start newscript
Note the use of chkconfig: - 99 99 .
This should be adapted with more useful priorities, basically 99 means that the initscript is started as one of the last scripts. Taking a look at $man chkconfig should prove useful.
The new script stores the pid of the newscript application in /var/run/mynewscript.pid
Note that it also stores things in /var/lock/subsys/
I have just had a look at the maintener file in the linux kernel Tree.
I have noticed that there are a number of orphaned project. The question is whether any of these orphaned project really needs to be taken care of.
Another interesting thing was to learn about the different scm and patching tools used in kernel development: git, quilt and hg.
Here is an interesting overview of the reason for the development of git and quilt.
I really start to like the patch approach, and the article linked above gives a good idea of the reasons to use this approach. I should try to summarise in a future post the advantages and disadvantages of the different source code management approaches.
I did some little things with kernel programming (or more compiling) these days.
Part of the things I did were compiling kernel because I wanted to try UML (user mode linux).
So that's what I did:
At that point some errors appeared, so I tried to correct them.
And all this in one day and half together with other things.
As I tend to forget pretty often the syntax of the query format of rpm, I had a short look at the internet. I found this web page which explains some aspects of the use of the rpm -q command.
I discovered a command which I did not know and which might turn out quite useful: namei. It follows the symbolic links until their end point can be found.
Example:
$> namei /usr/java/latest/
f: /usr/java/latest/
d /
d usr
d java
l latest -> /usr/java/jdk1.6.0_03
d /
d usr
d java
d jdk1.6.0_03
