...making Linux just a little more fun!



[ In reference to "Virtualization made Easy" in LG#144 ]

Drag Sidious [linlamer at cox.net]

Thu, 01 Nov 2007 18:42:51 -0500


You can thank a large part of Virtualbox's robustness on it's mature underpinnings. It's one of a large number of VM solutions based on Qemu code.

Other Qemu family members...

qemu-launcer -- gui to launch and manage qemu virtualization machines

qemu -- the original

kvm kernel modules and kvm application -- turns the Linux kernel into a hypervisor, userland portion is a hacked qemu. This takes advantage of the virtualization featues of newer AMD and Intel CPUS.

Win4Linux -- commercial application for running Windows on Linux.

Kqemu -- Accelerator for Qemu. Originally closed source kernel, it's open source ransom was paid by the Win4Linux folks and is now GPL.

The performance of KVM vs Kqemu vs Virtualbox vs Vmware vs Xen (running with full virtualization. Xen's paravirtualization approach is still easily the fastest)

It's good for not only desktop stuff, like virtualbox, but it can be very good for server stuff also.

It's not up to the same level as true hypervisors-based virtualization like with Vmware ESX or Xen (although as hardware vm support matures KVM is going to be big), but if you have a need for a couple servers and you don't have any spare space.. then Qemu (with KVM or Kqemu) is your man.

For example.. Qemu has a mode of operation were you can run it headless with the -nographic switch. Instead of a GUI box it will turn your console into a serial terminal. If you configure your host environment to use the serial console and then use Lilo's serial console support then you can effectively run your servers headless.

Then use screen to launch the VM and you can have multiplexed serial consoles for all your VMs on that machine.

Then there are lots of other clever things you can do with it like use LVM logical volumes as block devices for harddrives rather then loopback files and advanced networking with switching/router/firewalling.


[ In reference to "The Monthly Troubleshooter: Installing a Printer" in LG#130 ]

Ian Chapman [ian.chapman at alft.com]

Mon, 26 Nov 2007 11:22:20 -0500


Talking about Linux Epson stylus 660 problems. It has worked and I printed an Open office letter to my sister okay. But I was having problems with gnome type and other apps. This printer was fine under win 98 and since I have updated the HW I decided to get with modern software too. Only hick my printer may or may not work.

One of the frustrations is too many cooks and no chief. Lots of willing helper but not exactly plug and play. I have junked foomatic and ghostscript and just have cups and gutenprint and Ubuntu. All the detailed stuff about sending this that and the other to the printer is a waste of time. The printer is stuck in the middle of a job despite canning all jobs form both gnome and the Firefox type interface. Even switching off/on the printer seems to keep the job active somewhere. I exited a terminal window that I was using to send escputil stuff and the printer started up. It's really strange. Previously the gnome and Firefox interface could not detect the printer or parallel port. The color ink led was on and I even changed the ink cartridge to no avail. There was nothing wrong with the original.

Using the Firefox interface I have a choice of several drivers and no idea what to use. My printer prints the commands that it receives and does not do what the software is telling it. I am not really able to stop printing and have a clean start. Any ideas would be a great help as would be a reset button for both SW and HW.

Regards Ian.

Ian Chapman
302 Legget Drive
Kanata K2K-1Y5
613-287-0470 (227)

[ Thread continues here (13 messages/26.13kB) ]


[ In reference to "Migrating a Mail Server to Postfix/Cyrus/OpenLDAP" in LG#124 ]

René Pfeiffer [lynx at luchs.at]

Wed, 28 Nov 2007 23:37:41 +0100

Hello, Peter!

On Nov 28, 2007 at 1526 -0600, Peter Clark appeared and said:

> [...]
> I hope this is not an improper venue for seeking out information. If it is 20
> I apologize and will bugger off. If not, I am writing to you to ask a few
> questions about your Postfix/Cyrus/OpenLDAP article.

The Linuxgazette articles are meant to be useful, and if not then the authors usually answer any open questions or at least try to do that. :) We try to publish any useful answers, so this is why I sent my reply as copy to The Answer Gang list. This helps all people who have similar questions to find possible answers.

> I am not very experienced at all with OpenLDAP so that is where the thrust
> of my questions lay. I am trying to use your article and supplied
> configurations as a template and modifying as needed.

OpenLDAP isn't easy to set up, so you are in good company. This is not due to the software but to the concepts used in LDAP.

> In your tree design you show
> cn=webmail,ou=system,ou=accounts,dc=example,dc=net as a webmail account to
> do lookups but it is not referenced at all in the slapd.conf. How is that
> portion used.

slapd.conf only configures the basics of the OpenLDAP server process. You can define the directory where the LDAP tree is stored, the root account for the whole tree, the object class definitions to be used, SSL/TLS keys/certificates, indices and access rules. All this information is only used to start the server and then initialise the LDAP backend storage.

An entry such as "cn=webmail,ou=system,ou=accounts,dc=example,dc=net" is really a branch of the LDAP tree. This branch can either be a container for more branches or be an object of its own. The notation alone doesn't tell you what it is. You have to look for the object class of this entry. In my case I used "cn=webmail,ou=system,ou=accounts,dc=example,dc=net" as an example for an account object holding the password for access to the OpenLDAP server. The subsystem could connect to the OpenLDAP server, provide "cn=webmail,ou=system,ou=accounts,dc=example,dc=net" as a kind of login und authenticate with the password contained in the object referenced by "cn=webmail,ou=system,ou=accounts,dc=example,dc=net" in the tree.

That's what I meant by LDAP being a bit difficult to understand. You have branches which can be objects of classes and which can hold a variety of data. If the OpenLDAP servers sees that an object has a password attribute, it will allow a login with this password.

[ ... ]

[ Thread continues here (1 message/5.48kB) ]


[ In reference to "Easy Shell Scripting" in LG#133 ]

Mudassar Khan [mudassar at jumpgames.co.in]

Tue, 6 Nov 2007 18:07:42 +0530

Hello, I am new one for shell programming. I want to write a shell script that.. 1) Read text file from source folder and past it in to a destination folder

2) Delete previous text file from destination folder (destination folder contain only one text file at a time)

3) And this moving of file happened on weekly basis (after completion of a week new text file copied in destination folder in weekly basis)

4) Which file will be copied in the destination folder is decided by week. If it is 1st week then p1.txt, if week 5th then p5.txt will be copied in destination folder.

5) Week will be start from any date decided by us (like 14 December on Fridays to 22 December Friday is 1st week and other weeks will be calculated by 14 December ). Please help me.

Regards, Mudassar Khan

[ Thread continues here (2 messages/2.72kB) ]


[ In reference to "Rule-based DoS attacks prevention shell script" in LG#137 ]

diana [ephrondiana at gmail.com]

Fri, 02 Nov 2007 18:49:57 +0530


I was directed to you through talkback of the site -http://linuxgazette.net/137/takefuji.html. i got the following script from this site.but i am getting

ERROR message: "sed: -e expression #1, char 0: no previous regular 
expression Bad argument `DROP' Try `iptables -h' or 'iptables --help' 
for more information."while running that script manuall.
But i am getting the output from logs as dropped ip in my /etc/sysconfig/iptables.I am not sure of this error :'( .please help me.......

rm -f ttt
touch tmp
# disabled IPs can be obtained from /etc/sysconfig/iptables
grep DROP /etc/sysconfig/iptables|awk '{print $5}' >tmp
# ------------------------ DoS attacks rule -------------------------
#identity mismatch in secure
grep Did /var/log/secure|awk '{print $12}' >>tmp
#Invalid user
grep "Invalid user" /var/log/secure|awk '{print $10}' >>tmp
# Maximum login
grep "Maximum login" /var/log/secure|awk '{print $7}'|sed 's/.*\[\(.*\)\])/\1/g' >>tmp
# ------------------ reduce redundant IPs from tmp file -------------
size=`/usr/bin/wc tmp|awk '{print $1}'`
while test $i -lt $size
      us=`sed -n 1p tmp`
      sed /$us/d tmp >tmps
      echo $us >>ttt
      cp -f tmps tmp
      size=`/usr/bin/wc tmp|awk '{print $1}'`
rm -f tmp tmps temp0 temp
# ------------------ activate detected IPs --------------------------
size=`wc ttt|awk '{print $1}'`
size=`expr $size + 1`
/sbin/iptables -F
while test $i -lt $size
        ip=`sed -n "$i"p ttt`
        i=`expr $i + 1`
/sbin/iptables -A INPUT -s $ip -j DROP
# -----------------end of shell script test -------------------------  


[ Thread continues here (5 messages/6.08kB) ]


[ In reference to "Staying Connected" in LG#115 ]

Amit Kumar Saha [amitsaha.in at gmail.com]

Fri, 2 Nov 2007 23:23:43 +0530

Hi Ben,

The google.pl is really nice utility script, I modified it to use Mozilla Firefox

#!/usr/bin/perl -w
# Created by Ben Okopnik on Tue Feb 12 07:03:34 CST 2002
$browser = "/usr/bin/mozilla-firefox";
exec $browser, "http://www.google.com/advanced_search" unless @ARGV;
for ( @ARGV ){ s/.*/%22$&%22/ if y/ /+/; $s .= $s?"+$_":"$_"; }
# $ENV{LANG} = "en_US.UTF8";
exec $browser, "http://www.google.com/search?num=30&hl=en&as_qdr=all&q=$s&btnG=Google+Search"
Thanks, Amit

Amit Kumar Saha
*NetBeans Community Docs
Contribution Coordinator*
me blogs@ http://amitksaha.blogspot.com

[ Thread continues here (3 messages/2.55kB) ]

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Published in Issue 145 of Linux Gazette, December 2007