Tag: linux
TAP that DHCP bridge for some Qemu TUN in Fedora
by plouj on Jul.29, 2008, under HOWTO
The other day I needed to setup bridged networking for a Qemu virtual machine. Although I found a rather well written generic TAP interfaces guide on Wikibooks. It only explained how to configure a network bridge on a host machine with a static IP. I wanted to do this on a host that used DHCP. Plus I wanted to keep all configuration in Fedora specific places. Having discovered a good way to do this through experimentation after a few fruitless Google searches I thought it would be useful for myself and others to have the configuration documented here.
ifcfg-eth0
First, I changed the host’s (auto-generated) /etc/sysconfig/network-scripts/ifcfg-eth0 script from this:
# Attansic Technology Corp. L1 Gigabit Ethernet Adapter DEVICE=eth0 BOOTPROTO=dhcp HWADDR=00:1D:60:35:A7:64 ONBOOT=yes
to this:
# Attansic Technology Corp. L1 Gigabit Ethernet Adapter DEVICE=eth0 TYPE=Ethernet BRIDGE=br0 ONBOOT=yes
This turns off DHCP on the physical Ethernet device and just specifies that it will be connected to or a part of a bridge.
ifcfg-br0
Second, I created /etc/sysconfig/network-scripts/ifcfg-br0, which will be called to setup a bridge device:
DEVICE=br0 TYPE=Bridge BOOTPROTO=dhcp HWADDR=00:1D:60:35:A7:64 ONBOOT=yes DELAY=0 STP=off
As you can see, most of this configuration is copied from eth0 plus the bridge configuration as per the Qemu Wikibook.
qemu-ifup/down
Third, I shortened the /etc/qemu-ifup and /etc/qemu-ifdown from Wikibooks to get this:
/etc/qemu-ifup:
#!/bin/sh USER=$(id -un) sudo /usr/sbin/openvpn --mktun --dev $1 --user "$USER" sudo /sbin/ifconfig $1 0.0.0.0 promisc up sudo /usr/sbin/brctl addif br0 $1
/etc/qemu-ifdown:
#!/bin/sh sudo /sbin/ifconfig $1 down sudo /usr/sbin/brctl delif br0 $1 sudo /usr/sbin/openvpn --rmtun --dev $1
Here I basically removed all of the configuration that is taken care of in the sysconfig scripts. I also made explicit use of sudo simply because that is my preference.
Final steps
Now I can simply run /etc/qemu-ifup tap0 once to create a TAP device, and use something like: qemu-kvm -hda /virtual-machines/fedora9.disk -m 512 -net nic -net tap,ifname=tap0,script=no to start a virtual machine. When I’m done running the virtual machine, I can run /etc/qemu-ifdown tap0 to remove the TAP device.
All this sounds simple now that it’s working, but initially it took a lot of guessing on my part so I’m documenting it here for the future.
I would appreciate it if someone can point me to the official Redhat/Fedora documentation on editing /etc/sysconfig/network-scripts/ scripts.
Lexmark E250DN IPP Printing in CUPS
by plouj on Jun.22, 2008, under GNU/Linux
I just finished setting up my newly purchased monochrome duplex network printer – Lexmark E250DN. It took me a while to figure out how to configure CUPS on my GNU/Linux/Fedora machines to communicate with this printer. The problem was that I just didn’t know what URI to use for the printer. Unsurprisingly, the PDF and HTML documents that came with the printer didn’t mention such information. After all, why would Windows users need to know that if they can simply run the printer-specific utility to configure everything for them? Sheesh… Anyways. The CUPS manual was actually quite useful in listing common printer URIs. It turned out that the Lexmark URI lpd://printer-address/ps and a Generic PostScript driver worked quite well. In fact, the “/ps” part seems to be irrelevant, so simply lpd://printer.lan worked for me. However, the CUPS manual also suggested avoiding the LPD protocol if the printer supported other protocols. Using nmap I confirmed that my printer has at least something running on the IPP port (631):
$ nmap printer.lan Starting Nmap 4.53 ( http://insecure.org ) at 2008-06-22 20:39 EDT Interesting ports on printer.lan (10.1.1.7): Not shown: 1705 closed ports PORT STATE SERVICE 21/tcp open ftp 79/tcp open finger 80/tcp open http 515/tcp open printer 631/tcp open ipp 5001/tcp open commplex-link 8000/tcp open http-alt 9100/tcp open jetdirect 10000/tcp open snet-sensor-mgmt Nmap done: 1 IP address (1 host up) scanned in 0.396 seconds
After a bit of trial and error, I discovered that simply using the http://printer.lan:631 or ipp://printer.lan URI and a Generic PostScript driver worked without problems with E250DN.
Apart from these initial pains I am quite happy to be able to print double-sided black-and-white documents from all of my home computers.
Side Note:
During the investigation process, I noticed that Fedora’s system-config-printer utility prints the following information to the terminal when I tell it the IPP printer hostname:
...
printer.lan: /usr/lib/cups/backend/snmp "${HOST}" 2>/dev/null
printer.lan: hp-makeuri -c "${HOST}" 2> /dev/null
No ID match for device ipp://printer.lan:
<manufacturer>Lexmark</manufacturer>
<model>E250dn 6216N4G LE.PM.P121 -- Part Number -</model>
<description>Lexmark E250dn 6216N4G LE.PM.P121 -- Part Number -</description>
<commandset></commandset>
Using textonly.ppd
...
I wonder how I could get that XML-ish output myself. It doesn’t seem to come from hp-makeuri.
Google Summer of Code turned down for a Job
by plouj on May.19, 2008, under career
In April I was privileged to be one of the 1125 students who got selected for the Google Summer of Code (GSoC) 2008 program. I was accepted to work on a project to implement Panorama Viewing in VLC. This summer was my last chance to participate in GSoC as a student because of my graduation date so I was very excited to have this once in a lifetime opportunity. More recently, I received an offer for a full-time “Linux Application and OS Developer” position at SOMA Networks – a company in downtown Toronto. Given the importance of a permanent job and having read the advice from previous GSoC participants, it didn’t take me long to decide to cancel the GSoC project and focus on the new job. Due to timing, however, I still managed to receive an acceptance gift from Google. The gift is a book called Beautiful Code: Leading Programmers Explain How They Think. Apart from being an interesting read, it’s a nice souvenir to keep in memory of the many hours I spent preparing for GSoC by choosing a project to apply for and writing multiple proposals.
