Paths and line numbers are given for Ubuntu 7.04 Feisty Fawn, so if you’re on another distribution or another version of Ubuntu, your mileage may vary.

What we’ll do is add an XkbOption to the keyboard configuration files. At first, add the following at the end of /usr/share/X11/xkb/symbols/capslock:

partial hidden modifier_keys
xkb_symbols "escape" {
    key <CAPS> {        [       Escape  ]       };
    key <ESC>  {        [       None    ]       };
};

This defines an option that maps the CAPS and ESC key codes to the Escape and None symbols respectively. If you don’t want to disable the original Escape key, leave the corresponding line out. Now let’s give it an option name: insert the following line to /usr/share/X11/xkb/rules/base, somewhere around line 810, where the other capslock lines are:

caps:escape          =       +capslock(escape)

Now let’s add that option to the keyboard configuration in /etc/X11/xorg.conf: Find the InputDevice section for the keyboard and add the following line to the section:

        Option          "XkbOptions"    "caps:escape"

Now restart X by logging out and typing Ctrl-Alt-Backspace at the login prompt. That’s it. CapsLock is gone and on its place Escape stood in.

I wasn’t successful in convincing the XKeyboardConfig maintainer Sergej Udaltsov to accept a patch for this, but I attempted only once yet :)

Epiphany

1. Create a bookmark of a result page of the search engine (Ctrl-D)
2. Replace the search term with %s in the URL

Firefox

1. Write up an XML file according to the OpenSearch spec
2. Figure out how to load that file into Firefox
3. Figure out how to get that XML file right – Firefox just says that it doesn’t support this search engine
4. …

End of rant.

The outcome of the procedure is that you’ll have a second network card for your virtual machine, which you can configure from inside the virtual machine as if it was a real network card connected to the same ethernet as your real network card.

I assume that you either

• get your IP address with DHCP
• or have a static IP address

If you’re on DSL or cable modem with PPPoE you probably don’t want host networking, but NAT, which works out of the box.

We’re going to

1. create a virtual network interface
2. set up an ethernet bridge
3. add your physical network interface and the virtual interfaces to the bridge

Preparations

At first let’s install the needed software:

$ sudo apt-get install bridge-utils uml-utilities

The virtual network interface is configured with the package uml-utilities. uml stands for User Mode Linux, so understandably the package is preconfigured for use with User Mode Linux. In order to work correctly with VirtualBox, in /etc/network/if-pre-up.d/uml-utilities replace

chown root:uml-net /dev/net/tun

with

chown root:vboxusers /dev/net/tun

As we’re going to change the network configuration, we’re going to shut down the network. So don’t close this browser window :)

$ sudo /etc/init.d/networking stop

Creating a Virtual Network Interface

Now on to configuring the virtual network interface. Ubuntu and Debian store network configuration in the file /etc/network/interfaces. Assuming your network card is eth0, you’ll find a stanza beginning with the following in the file:

auto eth0
iface eth0 inet .....

Actually at install Ubuntu writes several such stanzas into the file so that they automatically work. Create a backup copy of /etc/network/interfaces (Now.) Then comment out all interfaces you don’t use so that NetworkManager doesn’t change the network configuration when we don’t want to. Leave in the lo interface, it’s required for local IP communication.

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet .....

#auto eth1
#iface eth1 inet dhcp

#auto ath0
#iface ath0 inet dhcp

#auto wlan0
#iface wlan0 inet dhcp

The next step is to create a virtual network interface. This is the network interface that will be used by the virtual machine. We don’t configure it – the virtual machine will do it. Add the following stanza under the lo interface:

auto tap0
iface tap0 inet manual
tunctl_user markus
uml_proxy_arp markus.mynetwork.loc
uml_proxy_ether eth0

Replace markus.mynetwork.loc with the host name or IP address you get from DHCP for your host machine (not the virtual machine). Also replace eth0 with your real network interface, if that is not eth0, and markus with your user name on the system. The user name set here will be the only user with permission to work with the virtual network interface.

Static IP address

If you have a static IP address, replace markus.mynetwork.loc instead with your static IP address.

Creating the bridge

Now we’ll set up the bridge. Add the following stanza after the tap0 stanza:

auto br0
iface br0 inet dhcp
bridge_ports eth0 tap0
bridge_maxwait 0

Static IP address

If you have a static IP address, you have to carry over the network settings from eth0 to br0. Assuming your eth0 stanza looks something like this:

auto eth0
iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.254

change the br0 stanza to look like this:

auto br0
iface br0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.254
bridge_ports eth0 tap0
bridge_maxwait 0

In any case, change the stanza for eth0 to the following:

auto eth0
iface eth0 inet manual

That’s it. Enable networking again:

$ sudo /etc/init.d/networking start

You can use ifconfig -a to see if all devices were correctly configured. You can now use host networking in VirtualBox. Enter tap0 in the interface name field. The fields setup application and terminate application can be left empty.

More than one virtual network interface

You can run more than one OS at the same time and have all them use host networking. Add a tap interface for all of them. Here’s an example for three virtual network interfaces:

auto tap0
iface tap0 inet manual
tunctl_user markus
uml_proxy_arp markus.mynetwork.loc
uml_proxy_ether eth0

auto tap1
iface tap1 inet manual
tunctl_user markus
uml_proxy_arp markus.mynetwork.loc
uml_proxy_ether eth0

auto tap2
iface tap2 inet manual
tunctl_user markus
uml_proxy_arp markus.mynetwork.loc
uml_proxy_ether eth0

auto br0
iface br0 inet dhcp
bridge_ports eth0 tap0 tap1 tap2
bridge_maxwait 0

Have fun, and let me know if that post was helpful to you :)

The reason is that windows software that adds meta tags to music files uses the default russian 8-bit encoding CP1251. All ID3 versions except for the newest ones only allow ISO-8859-1 as the tag encoding. So muine, according to the standard, interprets the tags in ISO-8859-1. Let’s change that.

I’m using Ubuntu 6.10. Let’s have a look at the muine sources:

~/src/deb$ apt-get install build-essential
~/src/deb$ apt-get source muine
...
dpkg-source: extracting muine in muine-0.8.5
dpkg-source: unpacking muine_0.8.5.orig.tar.gz
dpkg-source: applying ./muine_0.8.5-1ubuntu4.diff.gz
~/src/deb$ cd muine-0.8.5/
~/src/deb/muine-0.8.5$ ls src/
...
AddWindowEntry.cs             DndUtils.cs      Metadata.cs          SkipToWindow.cs
...

The file Metadata.cs looks like it’s responsible for the ID3 tags. Searching it for title shows the following lines:

                // Properties :: Title (get;)
                [DllImport ("libmuine")]
                private static extern IntPtr metadata_get_title (IntPtr metadata);

DllImport imports a binary library file. The next line declares a function metadata_get_title which is implemented in libmuine. Let’s look at that.

~/src/deb/muine-0.8.5$ ls libmuine/
...
gsequence.c  metadata.c   player-gst-0.8.c  rb-cell-renderer-pixbuf.c
...

Searching for title in metadata.c gives us the following line:

        metadata->title = get_mp3_comment_value (tag, ID3_FRAME_TITLE, 0);

Which leads us to get_mp3_comment_value. Let’s look at its definition:

get_mp3_comment_value (struct id3_tag *tag,
                       const char *field_name,
                       int index)
{
...
        frame = id3_tag_findframe (tag, field_name, 0);
...
        field = id3_frame_field (frame, 1);
...
        ucs4 = id3_field_getstrings (field, index);
...
        utf8 = id3_ucs4_utf8duplicate (ucs4);
...
}

get_mp3_comment_value calls a lot of functions the name of which starts with id3. The functions are not defined in metadata.c. They aren’t defined anywhere in the muine source code:

~/src/deb/muine-0.8.5$ grep -r id3_field_getstrings .
./libmuine/metadata.c:  latin1 = id3_ucs4_latin1duplicate (id3_field_getstrings (field, 0));
./libmuine/metadata.c:  ucs4 = id3_field_getstrings (field, index);

Only calls to that function. In metadata.c there’s an include statement that includes id3tag.h. Looks like what we need. Let’s download the source for the corresponding library:

~/src/deb/muine-0.8.5$ apt-cache search id3tag
libid3tag0 - ID3 tag reading library from the MAD project
libid3tag0-dev - ID3 tag reading library from the MAD project
mp3rename - Rename mp3 files based on id3tags
somaplayer - player audio for the soma suite
~/src/deb/muine-0.8.5$ cd ..
~/src/deb$ apt-get source libid3tag0
...
dpkg-source: extracting libid3tag in libid3tag-0.15.1b
dpkg-source: unpacking libid3tag_0.15.1b.orig.tar.gz
dpkg-source: applying ./libid3tag_0.15.1b-8.diff.gz
~/src/deb$ cd libid3tag-0.15.1b/
~/src/deb/libid3tag-0.15.1b$ grep -r id3_field_getstrings .
...
./field.c:id3_ucs4_t const *id3_field_getstrings(union id3_field const *field,
...

The function is defined in field.c. It accesses an array stringlist. That array is filled in the function id3_field_parse. This function calls another function, id3_parse_string that extracts the string values of a field.

~/src/deb/libid3tag-0.15.1b$ grep -r id3_parse_string *
parse.c:id3_ucs4_t *id3_parse_string(id3_byte_t const **ptr, id3_length_t length,
parse.h:id3_ucs4_t *id3_parse_string(id3_byte_t const **, id3_length_t,

This function is defined in parse.c. For ISO-8859-1 fields it calls id3_latin1_deserialize.

~/src/deb/libid3tag-0.15.1b$ grep -r id3_latin1_deserialize *
latin1.c:id3_ucs4_t *id3_latin1_deserialize(id3_byte_t const **ptr, id3_length_t length)
...

id3_latin1_deserialize is defined in latin1.c. It calls id3_latin1_decode to convert the latin1 string to UCS-4, which in turn calls id3_latin1_decodechar to convert a single character. We’re there: we have found the place we have to change:

/*
 * NAME:        latin1->decodechar()
 * DESCRIPTION: decode a (single) latin1 char into a single ucs4 char
 */
id3_length_t id3_latin1_decodechar(id3_latin1_t const *latin1,
                                   id3_ucs4_t *ucs4)
{
  *ucs4 = *latin1;

  return 1;
}

The function is very simple: ISO-8859-1 is a subset of unicode, so only a direct assignment is needed. For CP1251 things are different. Looking at the wikipedia page for CP1251, we see that the letters of the russian alphabet start at 0xC0 with the upper case letters, followed by the lower case letters to 0xFF. Using gnome-character-map, we find that the corresponding unicode code points are U+0410 through U+044F and that the letters are in the same order. Very convenient. Let’s change the function to return the correct unicode values for the CP1251 letters 0xC0 through 0xFF:

id3_length_t id3_latin1_decodechar(id3_latin1_t const *latin1,
				   id3_ucs4_t *ucs4)
{
  if (*latin1 >= 0xc0)
    *ucs4 = 0x410 + (*latin1 - 0xc0);
  else
    *ucs4 = *latin1;

  return 1;
}

The unicode encoding used here, UCS-4, just packs the unicode code point in a 32 bit integer, so we can just directly assign the unicode value. Now on to compiling the changed libid3tag.

~/src/deb/libid3tag-0.15.1b$ sudo apt-get build-dep libid3tag0
...
~/src/deb/libid3tag-0.15.1b$ sudo apt-get install fakeroot
...
~/src/deb/libid3tag-0.15.1b$ fakeroot dpkg-buildpackage -uc -us
...
~/src/deb/libid3tag-0.15.1b$ sudo dpkg -i ../libid3tag0_0.15.1b-8_i386.deb
...

Now let’s delete the muine song database so that it re-reads the metadata.

~/src/deb/libid3tag-0.15.1b$ rm ~/.gnome2/muine/*

Start muine and import the music file:

Победа! :)

Update: Added install of build-essential at the beginning.

I can generally recommend Marius Gdeminas’ blog, I found quite a lot of interesting things in there, including a link to his GTimeLog, Bash prompts: showing the command in the window title, xsel: the power of Unix, …

Gossip has been my favourite Jabber client for a long time. I like the simplicity and non-intrusiveness of its interface. But at work the standard IM network is ICQ. I’ve been using Gaim to connect to ICQ, but its interface has always bugged me.

The Jabber protocol provides for so-called transports, which enable you to talk to other IM networks while using Jabber on the client side. Gossip doesn’t support transports. But although that sounds like a deal-breaker, it isn’t. Transports work like this: you register on a jabber server and then sign up for a transport, providing your ICQ credentials. Then your ICQ contacts are available through UIN@transport.jabber.example.com, for example. After signing up for the transport using a transport-supporting client, you can use any Jabber client you like, and that includes Gossip. All your ICQ contacts will appear on the new account, and you can add other ICQ accounts using UIN@transport.jabber.example.com.

Now step-by-step for Ubuntu Dapper users:

1. Shut down Gossip.
2. Install gajim:
   1. Applications -> Add/Remove Software
   2. check “show applications without tech support”
   3. in the search field enter “gajim”
   4. check gajim and click OK
3. Start gajim through the Applications menu. It’s in “Internet”.
4. Add your existing jabber account to gajim.
5. Add a new account on a server that has a transport for ICQ (or whatever you need). I used jabber.freenet.de. This server has transports for AIM/ICQ, MSN, Yahoo, ICQv2 and IRC. You can see a list of accounts in Edit -> Accounts -> New -> Forward.

   Use the “Discover services” window to find out which transports are offered by a specific server.

   

   You can have both windows open at the same time.

6. Close the “Discover services” window and open it with your new jabber account.
7. Select the transport you want and click “Edit” or “Register”. You’ll be asked to provide the credentials for your ICQ/AIM/whatever account.
8. Close gajim.
9. Start gossip and add your account on the new server.

That’s it! All your ICQ contacts appear in Gossip. Add new ICQ contacts using UIN@icq.jabber.freenet.de (replace icq.jabber.freenet.de with the transport server you selected).

Digg this