Setting up a network adapter alias

sudo ifconfig eth0:[0-254] 192.168.1.2 up.

Instead of eth0 you can use any of existing interfaces

Firefox extension. Thoughts.

While I try to see into Firefox Extension development, I found not evident things for me. And here I'll list'em.

• You want to append event handler to created by you DOM-element somewhere in '1body' descendants. Don't try to use onclick or like it - you'll get a fail. Use addEventHandler method, and you'll get success :)
  

Django model field inheritance

To inherit model field in Django is not enough simply inherit a field class. It is needed to add attribute __metaclass__ = models.SubfieldBase. After that, you can overload any method you want.

Firefox extension. The first tries

I am developing the service which I'll describe further. And I decide to create a Firefox extension for it. And what I have dug:

• To create a developer profile may that
  

  firefox -profilemanager

• To run another -- development -- copy of Firefox
  

  firefox -no-remote -P <profile name>

And I assume firefox binary in your path.

Django and Oracle support

To get work Django and Oracle client in Ubuntu:

Download cx_Oracle (choose for your system), Oracle InstantClient and Sql*Plus (in this page you can choose your OS and download the packages (in my case are oracle-instantclient11.2-basic-11.2.0.0.2-1.x86_64.rpm and oracle-instantclient11.2-sqlplus-11.2.0.0.2-1.x86_64.rpm).

Move the files into one directory for simplicity and run

alien -k *.rpm
dpkg -i *.deb

to convert all the downloaded packages to ubuntu deb-format and install them.

Then make symlink to lib, otherwise module won't be found by Django

cd /usr/lib/python2.6
ln -s site-packages/cx_Oracle.so

To avoid

Traceback (most recent call last):
  File "", line 1, in 
ImportError: libclntsh.so.10.1: cannot open shared object file: No such file or directory

add to ~/.bashrc (or /etc/bash.bashrc to system-wide apply)

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib/oracle/11.2/client64/lib

If you see the message

Traceback (most recent call last):
  File "", line 1, in 
ImportError: libaio.so.1: cannot open shared object file: No such file or directory

run

sudo apt-get install -y libaio1

P.S. If you choose more modern (or older) version of Oracle IntstantClient you have to create symlinks for necessary version, e.g. you see the following error:

Traceback (most recent call last):
  File "", line 1, in 
ImportError: libclntsh.so.10.1: cannot open shared object file: No such file or directory

but in /usr/lib/oracle/11.2/client64/lib directory exists libclntsh.so.11.1. Just make it symbolic link with

ln -s libclntsh.so.11.1 libclntsh.so.10.1

Install RPM in Ubuntu

To install Rpm-package in Ubuntu Linux (to run commands needs to be a superuser or using sudo):

1. install alien package:

   sudo apt-get install alien

2. Convert Rpm to Deb (in current directory)
   

   alient -k <package-file>.rpm

3. Install the new Deb package
   

   dpkg -i <package-file>.deb

Problems with VPN-connections in Ubuntu Karmic

I need to connect to Cisco VPN. I had got a file with connection settings. Through NetworkManager I created new VPN connection by import the settings file. Trying to connect - no result. In /var/log/syslog I found the line:

NetworkManager: nm-vpn-connection.c.828: NeedSecrets failed: dbus-glib-error-quark Rejected se
nd message, 1 matched rules; type="method_call", sender=":1.5" (uid=0 pid=969 comm="NetworkManager) interface="org.freedeskt
op.NetworkManager.VPN.Plugin" member="NeedSecrets" error name="(unset)" requested_reply=0 destination="org.freedesktop.Netwo
rkManager.vpnc" (uid=0 pid=7971 comm="/usr/lib/network-manager-vpnc/nm-vpnc-service))

Some googling gives me a bit of information - Keyring manager denied connection of the VPN service. And how to grand access I didn't know. Googling more brings me the answer:
In /etc/dbus-1/system.d/nm-vpnc-service.conf

--- nm-vpnc-service.conf.fixed 2009-04-18 17:56:45.000000000 -0500
+++ nm-vpnc-service.conf 2009-04-18 17:57:37.000000000 -0500
@@ -6,6 +6,10 @@
   <allow own="org.freedesktop.NetworkManager.vpnc"/>
   <allow send_destination="org.freedesktop.NetworkManager.vpnc"/>
  </policy>
+ <policy user="at_console">
+  <allow own="org.freedesktop.NetworkManager.vpnc"/>
+  <allow send_destination="org.freedesktop.NetworkManager.vpnc"/>
+ </policy>
  <policy context="default">
   <deny own="org.freedesktop.NetworkManager.vpnc"/>
   <deny send_destination="org.freedesktop.NetworkManager.vpnc"/>

Ubuntu's Archive Manager and RAR-archives support

To add support of RAR-archives for Ubuntu's Archive Manager run

sudo apt-get install unrar

Disabled Mercurial's strip command

Mercurial command hg strip is disabled by default in Ubuntu. To enable it add to hgrc file (in .hg directory of repository or /etc/mercurial/hgrc) these lines
[extensions]
hgext.mq =

Reinstall Ubuntu automatically

There is a very simple command that reinstalls all the distribution packages and reconfigures them automatically. This is particularly helpful when you have done a partial upgrade and eventually have broken the system dependencies tree.

sudo dpkg-reconfigure -phigh -a

since this command would take a lot of time to process (~1 hour) depending on your hardware in case you have a minor dependency problem you can fix it via

sudo apt-get install -f

Source.

Create a MySQL database for new user

To create a database and a user, to grant some privileges:

CREATE DATABASE test_db DEFAULT CHARACTER SET UTF8;
CREATE USER 'user'@'%' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON test_db.* TO 'user'@'%';

Mercurial server in haste

Just now I need to pull to spontaneous remote Mercurial repository. I ran hg serve and have tried to push. The server rejects my connection, because it demands secure connection. Attempts to change protocol to HTTPS were failed.
As decision I found the following: in hgrc (or mercurial.ini in Windows) add

[web]

allow_push = *

push_ssl = false

Profit :)

Setting up Postgres database server in Ubuntu 9.10

Do all as the superuser.

apt-get install postgresql postgresql-client postgresql-contrib
# To reset password for postgres user
echo "ALTER USER postgres WITH PASSWORD 'postgres';" | sudo -u postgres psql template1
# reset password for system user
passwd postgres

In bottom of /etc/postgresql/8.4/main/pg_hba.conf file set as the following:

# DO NOT DISABLE!
# If you change this first entry you will need to make sure that the
# database
# super user can access the database using some other method.
# Noninteractive
# access to all databases is required during automatic maintenance
# (custom daily cronjobs, replication, and similar tasks).
#
# Database administrative login by UNIX sockets
local   all         postgres                          ident

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD

# "local" is for Unix domain socket connections only
local   all         all                               md5
# IPv4 local connections:
host    all         all         127.0.0.1/32          md5
# IPv6 local connections:
host    all         all         ::1/128               md5