Access scanner from LTSP server and thin clients

There seem to be a permission issue with accessing usb scanners from LTSP server and connected thin clients. Logging in as normal users, you cannot access the connected scanner.

Running the scanimage command as a normal user 
ltsp@ltsp-ProLiant-DL380-G4:~$ scanimage -L
device `hp3900:libusb:001:011' is a Unknown RTS8822 chipset based flatbed scanner

while logging in as the root user, running the scanimage command gives the parameter of the connected scanner.
root@ltsp-ProLiant-DL380-G4:~# scanimage -L
device `hp3900:libusb:001:011' is a Hewlett-Packard Scanjet 3800 flatbed scanner

You can however use any scan utility, but you will need root access to do this. To correct this - Looking at the permission for the usb character file
ltsp@ltsp-ProLiant-DL380-G4:~$ lsusb
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 005: ID 1c4f:0002 SiGma Micro
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 011: ID 03f0:2605 Hewlett-Packard ScanJet 3800c
Bus 001 Device 009: ID 03f0:5c17 Hewlett-Packard
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The user/group permission to the usb character device responsible for the connected usb device has read & write for the root user and group.
ltsp@ltsp-ProLiant-DL380-G4:~$ ls -l /dev/bus/usb/001

total 0
crw-rw-r--  1 root root 189,  0 2011-10-11 00:28 001
crw-rw-r--+ 1 root lp   189,  8 2011-10-11 13:03 009
crw-rw-r--+ 1 root root 189, 10 2011-10-11 09:17 011

Change the group from root to users. (In my case, the group users has all ltsp client users in that group)
root@ltsp-ProLiant-DL380-G4:/dev/bus/usb/001# chgrp users 011
root@ltsp-ProLiant-DL380-G4:/dev/bus/usb/001# ls -al
total 0
drwxr-xr-x  2 root root      100 2011-10-11 09:10 .
drwxr-xr-x  7 root root      140 2011-10-11 00:28 ..
crw-rw-r--  1 root root  189,  0 2011-10-11 00:28 001
crw-rw-r--+ 1 root lp    189,  8 2011-10-11 13:03 009
crw-rw-r--+ 1 root users 189, 10 2011-10-11 09:17 011

And now.......
ltsp@ltsp-ProLiant-DL380-G4:~$ scanimage -L
device `hp3900:libusb:001:011' is a Hewlett-Packard Scanjet 3800 flatbed scanner
ltsp@ltsp-ProLiant-DL380-G4:~$

Ubuntu 11.04 installation hangs on timezone selection

When installing Ubuntu 11.04, the installation process hangs on time zone selection.  The installation hangs because of your network (Internet) connection.

The trick in dealing with this is disable your network connection and restart the installation.

Drupal Internal links don't work after migration

In some cases, after migrating all internal links in drupal defaults to the homepage. If you encounter this issue, enable mod_rewrite in Apache.

For Ubuntu users,

sudo a2enmod rewrite

Restart Apache

sudo /etc/init.d/apache2 restart

 
You can also.......
(a) make sure that you have Drupal's .htaccess file
(b) make sure that the apache vhost which controls your site does not contain an AllowOverrides None which disables .htaccess files in your site's directory. Change it to AllowOverrides All

Moodle 2.1.1 - Redirect to 'My Moodle' page after user logon

To redirect users to their course page referred to as 'My Moodle' page after login in moodle 2.1.1,

Click on Site administrator -> Appearance -> Navigation -> Default home page for users -> My Moodle

Moodle 2.0 - Convert database engine from MyISAM to InnoDB

This scenario usually occurs when you upgrade moodle. If upgrading from moodle-1.9 to moodle-2.1.1, there is a database engine compatibility issue.

In the moodle notification page, the message below usually pops up:
Database tables are using MyISAM database engine, it is recommended to use ACID compliant engine with full transaction support such as InnoDB.

To convert your database engine to InnoDB, run the innodb.php script in the directory of the admin directory which is resident in the moodle directory.
http://moodlesite.domain/admin/innodb.php
 
Replace moodlesite.domain with you moodle path or IP address.

Enable Apache "public_html" for users in Ubuntu 10.04

Enable mod_userdir, which is installed by default with Apache2.  
sudo a2enmod userdir   

Create public_html directory with the user's permissions
mkdir public_html   

I don't know if that is a bug or a feature. Edit file /etc/apache2/mods-available/php5.conf and comment out lines

...IfModule mod_userdir.c...

        ...Directory /home/*/public_html..

        ...php_admin_value engine Off
        .../Directory

    .../IfModule...

Restart Apache Finally, you should restart Apache.  
sudo /etc/init.d/apache2 restart  

You can test with http://localhost/~username  or http://ip-address-of-system/~username

How to configure rpm/debian package manager to use proxy

To configure package manager to use proxy in fedora, CentOS, ubuntu or generally any rpm/debian based linux, you will need to enter your proxy login details in apt.conf (for debian based) and yum.conf (for rpm based).


For RPM Based
Create or edit /etc/yum.conf and add the details below, replacing proxy-server, port, username and password with your own login details.

# The proxy server - proxy server:port number
proxy=http://proxy-server:port 
# The proxy account details 
proxy_username=username
proxy_password=password

For DEBIAN Based

Create or edit /etc/apt/apt.conf and add the details below, replacing proxy-server, port, username and password with your own login details.

ACQUIRE {
http::proxy "http://username:password@proxy-server:port/"
}