# A (writable) DNS filesystem


I've extended the 
[DNS filesystem](/2010/december/04/a_dns_filesystem/index.html)
a bit and added the possibility to 
`WRITE` to it. This only works for zones which utilize [dynamic
updates](http://docstore.mik.ua/orelly/networking_2ndEd/dns/ch10_02.htm).

> You can now mount the world and write to it!

Also `TSIG` should be supported (but I have not tested it - as I'm
lazy). For `TSIG` you need a file (named "dynupdate" here with the
following):

    # domain           tsig-key name       key
    miek.nl            tsig-key            awwLOTrFPge+rRKF2+DEiw==

Code is still contained in a single [Perl
file](/downloads/2010/dns.pl-0.2).


I've create a dynamic zone for `dyn.miek.nl`, so lets see how it works:

    $ ./dns.pl dynupdate theworld       # start our filesystem
    $ cd NL/MIEK/
    $ ls
    a  mx  ns  soa  txt
    $ cat txt
    MIEK.NL.    86400   IN  TXT "$Hash: edf130d 2010-08-25 08:29:16 +0200 Miek Gieben$"
    ## So far nothing new
   
Now lets write:

    $ cd DYN
    $ ls
    a  mx  ns  soa  txt
    ## We have a name: dyn.miek.nl with the following addresses:
    $ cat a         # show the a-records dyn.miek.nl
    DYN.MIEK.NL.    4000    IN  A   127.0.0.2
    DYN.MIEK.NL.    4000    IN  A   127.0.0.1
    ## Lets add another
    $ echo "dyn.miek.nl 4000 IN A 127.0.0.3" > a   
    $ cat a
    DYN.MIEK.NL.    4000    IN  A   127.0.0.3
    DYN.MIEK.NL.    4000    IN  A   127.0.0.2
    DYN.MIEK.NL.    4000    IN  A   127.0.0.1
   
It does not really matter what filename you use, because
it currently looks only at the content you write.

    # adding new name: c.dyn.miek.nl
    $ echo "c.dyn.miek.nl 30 IN A 127.0.0.1" > a    # note: still "a"
    # cat C/a    # show the a-record in the directory C
    C.DYN.MIEK.NL.  30  IN  A   127.0.0.1
    #
    # Perform an illegal write:
    $ echo "miek.nl 30 IN A 127.0.0.1" > a  # isn't a dynamic zone
    echo: write error: invalid argument

Things you might want to add to this code:

* with `mkdir` create a delegation (easy: just add NS records);
* with `rmdir` delete a delegation;
* with `unlink` delete records;
* Anything else you can think of;
* Again: [the code](downloads/2010/dns.pl-0.2).