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showing posts tagged with 'linux'
Securely clearing a harddisk
edited by on April 29th 2007, at 19:40
There are two things you need:

A bootable linux LiveCD, preferrably Knoppix, but any other distro with all basic linux tools will do.

Some knowledge on how to use commandline based programs (and perhaps some knowledge with linux in general).

First, make sure to boot with your LiveCD. You won't need to boot entirely into the graphical interface.
For Knoppix, the boot: commandline would be something like:

boot: knoppix 2 lang=your-keyboard-layout vga=normal

You can leave out the vga=normal to use framebuffer instead of plain text mode. Replace your-keyboard-layout (keyboard layout) with your country code: for Belgium (azerty), this would be lang=be; for standard US (qwerty), use lang=  ...
 
A thing or two about kernel frequency
edited by on April 28th 2007, at 00:46
In short: the kernel frequency is the number of interrupts (IRQs) handled by the kernel per second. Like most applications of frequency, it's also expressed at Hz (hertz).

A more sound explanation of interrupts can be found here, but it basically boils down to this: an interrupt is generated each time an event on a piece of hardware (in the most elementary way; this includes your keyboard for instance), and requires the necessary CPU time to handle that event. This is called interrupt handling.

Now, because the kernel directly interacts with all the hardware around, it's vital to have it handle interrupts; actually, it's the kernel that handles interrupts, by using the CPU.

Very simple: t  ...
 
Input trouble with PuTTY SSH on Debian
edited by on April 28th 2007, at 00:37
If you happen to have keyboard trouble when you SSH with PuTTY to a Debian system, you might want to read on.
With trouble, I mean one or more of the following symptoms:

Numeric keypad not working, even with numlock enabled/disabled

Home/End keys not working as they should

Function keys not working as they should

Other weirdness concerning keyboard...

We've figured out a possible solution to the problem. It has been tested (and used) extensively by my and a collegue, and have found it working perfectly on Debian Woody and Debian Sarge.
It may be possible that these settings also work on other distros having similar problems. If it does, please let us know so we can add it to the article  ...
 
Sync your website with rsync
edited by on April 28th 2007, at 00:18
If you are blessed with ssh access to your webhosting, then a world of goodies opens up. One of these is rsync. When installed on your webhosting (which usually is), you can use this instead of ftp to maintain your website.

Rsync is mainly used for syncing two file structures (directories and subdirectories) together. It works by comparing the two structures and check out each directory and files on modified date and time, but also content of the file (using hashes).
While mostly used for backup, this thingy is very handy when maintaining a website. Rather than figuring out which files need to be copied, rsync does it all for you with a single command.

rsync -e ssh -rltDv <local website  ...
 
'screen': add a status bar
edited by on April 27th 2007, at 23:56

Copy the following code into your ~/.screenrc
Or if you want to add the statusbar globally, add it to /etc/screenrc.

# An alternative hardstatus to display a bar at the bottom listing the
# windownames and highlighting the current windowname in blue. (This is only
# enabled if there is no hardstatus setting for your terminal)
hardstatus on
hardstatus alwayslastline
hardstatus string "%{.bW}%-w%{.rW}%n %t%{-}%+w %=%{..G} %H %{..Y} %m/%d%C%a "

When running screen, the result should look similar to this:

 
Limiting software RAID resync speed
edited by on April 26th 2007, at 22:34
Every now and then, one might need to resync one or more disks that were in a linux software RAID array. This usually is not a problem at all, but once in a while (in particular on SATA controllers), the resync takes up a lot of system resources, regardless of the fact that the resync doesn't exclusively uses bandwidth (i.e. it only uses the free available bandwidth).
In this case it may be necessary to cap the maximum resync speed limit to a lesser value, so a bit of bandwidth becomes free again, seriously reducing the I/O load.

Changing the maximum and minimum speed limits is easy. Like most system things, this is done by echoing the desired speed to a file in the /proc filesystem:

To se  ...
 
Using DSPAM 3.6.x as a spamfilter on KMail
edited by on April 23rd 2007, at 23:33
Spam nowadays is a real pain. While linux users are fairly safe against most common viiri and spyware, spam mail affects everyone.
While there are many spamfilters out there, I've found that only one is pretty effective, on the long run as well. This guide provides a solution to implementing this filter into KMail for local scanning, filtering and retraining.

A working KMail configuration for scanning and retraining spamfilter with POP3 accounts (IMAP is not supported because mail doesn't really get "downloaded").

A DSPAM 3.6.x using the hash_drv, with training data stored in the user's homedir (~/.dspam)

KMail (of course)

A sane build environment (gcc and co)

Superuser access (for DSPA  ...
 
Installing Gentoo in VMware
edited by on April 3rd 2007, at 17:28

Found this article to be useful while installing a Gentoo in a virtual machine for VMware:
http://gentoo-wiki.com/HOWTO_Install_Gentoo_on_VMware_in_Windows_NT/2K/XP

I found the kernel configuration portion particularly useful, especially since I managed to enable every SCSI controller and network adapter accept the one I needed.

 
VMware Server Console on Ubuntu 6.10 Edgy
edited by on March 28th 2007, at 11:10

If VMware Server Console doesn't work on your Ubuntu 6.10 Edgy install, here's what to do.

If after installing, the console does not launch, but instead takes up 100% CPU until the end of days (or until you kill it), try starting the console with this command:

LD_PRELOAD=/usr/lib/libdbus-1.so.3:$LD_PRELOAD vmware-server-console

This fixes some yet to be resolved issue around shared libs.

 
XFS on server
edited by on March 26th 2007, at 21:12
In my trial runs of various filesystems, I decided to convert the data partition of my server/devel pc from ReiserFS to XFS...

Steps are quite short. Since convertfs is highly discouraged, I did it the long way:

I used dar to pack the data partition and moved it to external storage.

Did mkfs (read below).

Extract the thing back to the data parition.

Since XFS is a bit sluggish, I followed the forum thread at http://forums.gentoo.org/viewtopic-t-488215.html to speed things up a bit. I used the following for mkfs:

mkfs.xfs -l internal,size=128m -d agcount=2 /dev/sda6

The explanation for all these parameters can be found in the forum thread I mentioned earlier.

This allows for a bit mor  ...
 
Reiser4 on laptop
edited by on March 26th 2007, at 20:48
Did (again) a reinstall of my laptop to get rid of all the funny unused packages and software (which was quite needed). Well, the other real reason was for me to test out a new filesystem. While my original plan was to go with XFS, I decided to try on Reiser4.

Installation was not a real easy task: while Gentoo can be installed through virtual any LiveCD (yeah Gentoo), there are not much livecd's out there with new enough (2.6.17+) reiser4 support, and even less cd's that are on top of that 64bit. In fact, I found none.

Since it's impossible to chroot into a 64bit system when running a 32bit kernel, I had to pull some stunts to get my reiser4 installed on Gentoo.

I used these resources:

  ...
 
PHP with MSSQL on Debian/Ubuntu
edited by on March 26th 2007, at 20:08
Apparently, there's no package for MS-SQL support in Debian or Ubuntu. Why this is, is not very known, in particular since there is MS-SQL support in PHP4 and PHP5.
I found the following steps somewhere on the internet.

The following was tested on a Ubuntu 6.10 Edgy, but will probably work on others as well.
Also, whenever I refer to php5, it could well be replaced with php4, which I've tested as well.

First of, make sure the necessary build tools are installed:
# apt-get install build-essential debhelper

It's possible more tools are needed, depending on which ones have already been installed, but basically, if you can compile other packages from source, you should be good to go.

Next up  ...
 
IEs4linux: installing Internet Explorer on linux
edited by on February 11th 2007, at 19:50
Installing Internet Explorer was never so easy with IEs4linux, a script that does all the work for you. Download and try it now: http://www.tatanka.com.br/ies4linux/.

It's really easy, but here's how I did it. Note that the instructions are also on the website of IEs4linux.

First, make sure the required software is installed:

wine: very obvious, you need this to run the installed IEs;

cabextract: required to unpack the CAB files that get downloaded.

You don't need to backup your current ~/.wine/ directory, as IEs4linux created a separate profile for the IEs. If you do happen to need IE for your other apps, it's best to start with a clean profile, as a profile with other apps installed   ...
 
Gentoo 2006.1: module autoload woes after upgrading udev
edited by on February 10th 2007, at 19:06
Was upgrading a bit on my laptop (amd64), and this included udev and baselayout.
After a reboot, my whole system did funny things. All was retraceable to one thing: the system was automatically loading modules as it pleases, which caused all kinds of problems...

I have a pretty custom configured system concerning hardware.
By default, I only use wireless, and thus don't load the local netif modules (Realtek 8139) and definitely not the IEEE1394 (Firewire) link, as I very rarely us this for networking (and when I do, it's mainly for high-speed p2p transfer - no I don't have gigabit network).
Secondly, I have both my onboard sound card, as well as my Audigy 2 PCCARD configured. Naturally, the  ...
 
Upgrading your OpenWRT to rc6
edited by on January 31st 2007, at 20:50
Did an upgrade of my Linksys WRT54GL to the latest OpenWRT firmware. These are roughly the steps I followed.

My old firmware was a OpenWRT rc5, default release. For my new firmware, I used the ImageBuilder to create a more customized firmware with a lot of packages (such as ntpclient, openvpn, nas, gpio, ...) preinstalled in the squashfs image. I left the new Webif^2 out on purpose, as it's updated at a fair regular base. The image (which has it's build list attached) is called cad, which is because I originally selected it for use with routers at work.

Anyway, updating my WRT54GL, was not as straight-forward as I had hoped. The upgrade firmware function of both Webif and Webif^2 did not w  ...
 
Linksys Programming: introduction...
edited by on January 30th 2007, at 23:07
For work, I started experimenting with writing C programs for (flashed) Linksys WRT54GL routers.

Basically, the WRT54GL routers are running OpenWRT, a very lightweight linux distro, specifically designed for those type of routers. The router uses a Broadcom CPU, and uses the MIPS architecture. For more information, check the OpenWRT site at http://openwrt.org/.

At first, I was a bit worried about the differences between the full availability of the GNU C Libary, and the very slim version on the OpenWRT distro. Luckily, I quickly found out that the C Library on OpenWRT has the most used functions well covered.

Compiling C programs for MIPS might seem tricky (since you can't plainly fire up  ...
 
Monitor disk i/o in linux
edited by on December 18th 2006, at 16:57

Ever wondered how much disk i/o is taking place on your linux-based server (or workstation)?

Here are some commands:

iostat

The iostat makes a snapshot of each available physical volume, and shows the current reads and writes of the volumes.

dstat -dnyc -f 5

dstat is a more advanced code, and measures both disk i/o as well as network i/o in near realtime.

 
Anatomy of Postfix
edited by on November 27th 2006, at 21:28

Got this link from a colleague:
http://www.linuxjournal.com/article/9454

It describes the inner workings of Postfix, the well-known mailserver for Linux.

 
showing posts tagged with 'linux'
 
 
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