-
Den norske bokbransjen har
-bedt om at
-digitale bøker må få mva-fritak slik papirbøker har det, og
-finansdepartementet
-har sagt nei. Det er et interessant spørsmål om digitale bøker
-bør ha mva-fritak eller ikke, og svaret er ikke så enkelt som et ja
-eller nei.
-Enkelte
-medlemmer av bokbransjen truer med å droppe den planlagte
-lanseringen av norske digitale bøker med digitale restriksjonsmekanismer
-(DRM) som de har snakket om å gjennomføre nå i vår, og det må de
-gjerne gjøre for min del.
-
-
Papirbøker har mva-fritak pga. at de fremmer kultur- og
-kunnskapsspredning. Digitale bøker uten digitale
-restriksjonsmekanismer (DRM) fremmer kultur- og kunnskapsspredning,
-mens digitale bøker med DRM hindrer kultur og kunnskapsspredning.
-Digitale bøker uten DRM bør få mva-fritak da det er salg av bøker på
-lik linje med salg av papirbøker, mens digitale bøker med DRM ikke bør
-få det da det er utleie av bøker og ikke salg.
-
-
Jeg foretrekker å kjøpe bøker, og velger dermed å la være å bruke
-DRM-belastede digitale bøker. Vet ikke helt hva jeg ville være villig
-til å betale for å leie en bok, men tror ikke det er mange kronene.
-Heldigvis er det mye bøker tilgjengelig uten slike restriksjoner, og
-de som vil ha tak i engelske bøker kan laste ned bøker som er
-tilgjengelig uten bruksbegresninger fra The
-Internet Archive. Der er det pr. i dag 1 889 313 bøker
-tilgjengelig. De er tilgjengelig i flere formater. Besøk
-oversikten over tekster
-der for å se hva de har.
+
As reported earlier, the last few days I have looked at how Debian
+Edu clients are configured, and tried to get rid of all hardcoded
+configuration settings on the clients. I believe the work to be
+mostly done, and the clients seem to work just fine with dynamically
+generated configuration.
+
+
What is the point, you might ask? The point is to allow a Debian
+Edu desktop to integrate into an existing network infrastructure
+without any manual configuration.
+
+
This is what happens when installing a Debian Edu client here at
+the University of Oslo using PXE. With the PXE installation, I am
+asked for language (Norwegian Bokmål), locality (Norway) and keyboard
+layout (no-latin1), Debian Edu profile (Roaming Workstation), if I
+accept to reformat the hard drive (yes), if I want to submit info to
+popcon.debian.org (no) and root password (secret). After answering
+these questions, the installer goes ahead and does its thing, and
+after around 50 minutes it is done. I press enter to finish the
+installation, and the machine reboots into KDE. When the machine is
+ready and kdm asks for login information, I enter my university
+username and password, am told by kdm that a local home directory has
+been created and that I must log in again, and finally log in with the
+same username and password to the KDE 4.4 desktop. At no point during
+this process did it ask for university specific settings, and all the
+required configuration was dynamically detected using information
+fetched via DHCP and DNS. The roaming workstation is now ready for
+use.
+
+
How was this done, you might wonder? First of all, here is the
+list of things that need to be configured on the client to get it
+working properly out of the box:
+
+
+- IP address/netmask and DNS server.
+- Web proxy URL.
+- LDAP server for NSS directory information (user, group, etc).
+- Kerberos server for PAM password checking.
+- SMB mount point to access the network home directory. (*)
+- Central syslog server to send syslog messages to. (*)
+- Sitesummary collector URL to submit info to central server. (*)
+
+
+
(Hm, did I forget anything? Let me knew if I did.)
+
+
The points marked (*) are not required to be able to use the
+machine, but needed to provide central storage and allowing system
+administrators to track their machines. Since yesterday, everything
+but the sitesummary collector URL is dynamically discovered at boot
+and installation time in the svn version of Debian Edu.
+
+
The IP and DNS setup is fetched during boot using DHCP as usual.
+When a DHCP update arrives, the proxy setup is updated by looking for
+http://wpat/wpad.dat and using the content of this WPAD file to
+configure the http and ftp proxy in /etc/environment and
+/etc/apt/apt.conf. I decided to update the proxy setup using a DHCP
+hook to ensure that the client stops using the Debian Edu proxy when
+it is moved outside the Debian Edu network, and instead uses any local
+proxy present on the new network when it moves around.
+
+
The DNS names of the LDAP, Kerberos and syslog server and related
+configuration are generated using DNS information at boot. First the
+installer looks for a host named ldap in the current DNS domain. If
+not found, it looks for _ldap._tcp SRV records in DNS instead. If an
+LDAP server is found, its root DSE entry is requested and the
+attributes namingContexts and defaultNamingContext are used to
+determine which LDAP base to use for NSS. If there are several
+namingContexts attibutes and the defaultNamingContext is present, that
+LDAP subtree is used as the base. If defaultNamingContext is missing,
+the subtrees listed as namingContexts are searched in sequence for any
+object with class posixAccount or posixGroup, and the first one with
+such an object is used as the LDAP base. For Kerberos, a similar
+search is done by first looking for a host named kerberos, and then
+for the _kerberos._tcp SRV record. I've been unable to find a way to
+look up the Kerberos realm, so for this the upper case string of the
+current DNS domain is used.
+
+
For the syslog server, the hosts syslog and loghost are searched
+for, and the _syslog._udp SRV record is consulted if no such host is
+found. This algorithm works for both Debian Edu and the University of
+Oslo. A similar strategy would work for locating the sitesummary
+server, but have not been implemented yet. I decided to fetch and
+save these settings during installation, to make sure moving to a
+different network does not change the set of users being allowed to
+log in nor the passwords required to log in. Usernames and passwords
+will be cached by sssd when the user logs in on the Debian Edu
+network, and will not change as the laptop move around. For a
+non-roaming machine, there is no caching, but given that it is
+supposed to stay in place it should not matter much. Perhaps we
+should switch those to use sssd too?
+
+
The user's SMB mount point for the network home directory is
+located when the user logs in for the first time. The LDAP server is
+consulted to look for the user's LDAP object and the sambaHomePath
+attribute is used if found. If it isn't found, the home directory
+path fetched from NSS is used instead. Assuming the path is of the
+form /site/server/directory/username, the second part is looked up in
+DNS and used to generate a SMB URL of the form
+smb://server.domain/username. This algorithm works for both Debian
+edu and the University of Oslo. Perhaps there are better attributes
+to use or a better algorithm that works for more sites, but this will
+do for now. :)
+
+
This work should make it easier to integrate the Debian Edu clients
+into any LDAP/Kerberos infrastructure, and make the current setup even
+more flexible than before. I suspect it will also work for thin
+client servers, allowing one to easily set up LTSP and hook it into a
+existing network infrastructure, but I have not had time to test this
+yet.
+
+
If you want to help out with implementing these things for Debian
+Edu, please contact us on debian-edu@lists.debian.org.
+
+
Update 2010-08-09: Simon Farnsworth gave me a heads-up on how to
+detect Kerberos realm from DNS, by looking for _kerberos TXT entries
+before falling back to the upper case DNS domain name. Will have to
+implement it for Debian Edu. :)
