LIS654lecture 3 omeka installation and system overview start Thomas Krichel

this lecture Introduction to the Internet. Introduction to wotan. Introduction to omeka.

Internet application protocols Most of the time in digital libraries, we assume that Internet access works. What we need are protocols that make the Internet do something useful. Such protocols are called Internet application protocols. The most important one of them is the domain name system.

Domain Name System Domain Name System allows us to associate human- friendly names with IP addresses. These names are called domains names. Domain names can be leased from domain nate registrars. A machine with a domain name on the Internet is called a host. When we know the domain name of the host, we can communicate with the host.

protocols to communicate with hosts There are two protocol we use in this class. – We use http to work with the omeka web interface – We use ssh for some special operations. Both protocols are client/server protocols. You run as ssh or http client on your local machine. You communicate with a machine that runs ssh or http server software.

the ssh protocol ssh is protocol that uses public key cryptography to encrypt a stream of communication between client and server. This allows us to privately manipulate the server. Or “manipulations” are really just changes to files on the server that contain our web pages. The ssh client software we use on the PC is called WinSCP. It is a file transfer program.

the host key When an ssh client opens a connection with a host, it requests its key. If you have not connected to the host before, you get a warning that your ssh client does not know the host with that key. When you accept, your ssh client remembers the key. If you connect to the a host you have a key stored for and the key changes, your ssh client will warn you. This may be a host controlled by a mafioso.

our server Is the machine wotan.liu.edu We also say it is a “host” on the Internet. wotan is the head of the gods in the Germanic legend. The name has nothing to do with Chinese food. It is a humble PC. It runs the testing version of Debian/GNU Linux. It runs both http and ssh server software. It is maintained by Thomas Krichel.

user name & password To open a meaningful ssh session on wotan, you need a use name and a password. You can choose your user name as a short form of your own name. It should be all lowercases and can not have spaces. Please don't choose an insecure password.

the web site As part of the course, you are being provided with web space on the server wotan.liu.edu, at the URL where user is a user name that you have chosen. This shows a list of available fails as prepared by the web server at wotan. This is a page that Thomas has prepared for you.

omeka Omeka is an open-source software for image- based repositories. Each of you gets a complete installation of omeka installed in your home directory. Omeka uses PHP [2 slides]. Omeka uses mySQL [2 slides].

PHP Omeka is written in PHP. PHP is the PHP Hypertext Processor, a high level scripting language. PHP code is interpreted by the web server. On wotan we run the Apache web server. Apache on wotan is configured in such a way as to interpret PHP.

Apache interprets PHP When Apache on wotan finds a file that has the ending.php, it does not send it to the web client directly. Instead it scans the page for special processing instructions, and sends these processing instructions to a PHP interpreter. Then it sends the processed code (usually in HTML) to the client. This verry slow and inefficient.

mySQL Omeka uses the mySQL database system to store data. It keeps as set of databases. Your database has the same name as your user name. The database was created by Thomas before today’s class by running the mySQL commands CREATE DATABASE user; GRANT ALL ON user.* to IDENTIFIED BY 'secret' WITH GRANT OPTION; where user is your username and secret is your secret word.

the PHPmyadmin site At we have the PHPmyadmin installation. PHPmyadmin is a web interface, written for the administration of mySQL, written in PHP. Thus you don’t have to learn mySQL commands. You gain access to the interface by login with your user name and your secret word.

the omeka site As part of the course, you are being provided with web space on the server wotan.liu.edu, at the URL where user is a user name that you have chosen. This URL will initially redirect to an initialization screen. Fill it out.

omeka’s mySQL tables Each database has a set of tables inside. The tables that omeka creates, and then uses, all have a name starting with “omeka_”. You can create other tables in your mySQL database but choose names that don’t start with “omeka_”. You can see the tables created once you have filled out the installation form.

some generalities about Debian Debian is an open-source computer operating system developed and maintained by a large group of volunteer. Debian packages together a very large set of pieces of software into a coherent system. Wotan runs the testing version. It provides a version of the UNIX operating system using Linux.

files, directories and links Files are continuous chunks data on disks that are required for software applications. Directories are files that contain other files. Microsoft calls them folders. In UNIX, the directory separator is “/” The top directory is “/” on its own.

users and groups “root” is the user name of the superuser. The superuser has all privileges. There are other physical users, i.e. persons using the machine There are users that are virtual, usually created to run a daemon. For example, the web sever in run by a user www-data. Arbitrary users can be put together in groups.

permission model Permission of files are given –to the owner of the file –to the group of the file –and to the rest of the world A group is a grouping of users. Unix allows to define any number of groups and make users a member of it. The rest of the world are all other users who have access to the system. That includes www-data!

winscp In winscp, the client that we use here most of the time, we don't make advanced use of public keys, we simply give a password. Note that winscp does not establish a connection to wotan. It simply uses ssh as a means to transfer files. When winscp saves a file, it may require to open a new connection and will ask you the password again. This request may be in a window you can't immediately see.

ssh and mac os/x In the past I told Mac users to investigate investigate a software called fugu: A student made me aware of TextWrangler at – This is an editor, not an ssh client but – It has support for remote file storing via ssh. – I think it also has a HTML editing mode. – My student was pleased with it.

open a wotan session with winscp If you see a list of session, click on “new session”. – The host name is “wotan.liu.edu”. – Give your user name. – Click on “save”, this will save the session, after “ok”. You will be lead to the list of saved sessions, double- click to open a session. At initial connection, you will be shown a warning message that you can ignore. When saving or duplicating files, you may be asked to enter your password again. Watch out for that.

home directory When your connection with wotan, and you have authenticated as a certain user, you will be shown your home directory. On wotan this is /home/user where user is your user name. There you see a bunch of files starting with a dot. Leave them alone. And you see a bunch of directories.

initial files on wotan A directory called public_html. This is your web site. A directory called omeka-version where version is a version number. A symbolic link (aka symlink, aka shortcut) called omeka leading to omeka-version. This there for updating the installation later.

web home directory The web home directory is /var/www. There you see a directory home, with a series of links – they have a user name as file name – they go to your home/public_html directory There you see a directory omeka with a series of links – they have a user name as file name – they go to your omeka directory

web site address goes to the /var/www directory. There it shows the file index.html. goes to the /var/www/home directory, where it finds the link to the public_html directory of the user user. goes to the /var/www/omeka directory, where it finds the link to the omeka directory. There it shows index.php.

the admin interface The admin interface for your omeka site is at You simply add ‘admin’ to your omeka address. For trivial security, there is no link to this place. Bookmark it in your browser.

omeka/db.ini This contains the instructions that allow to connect to your database. Since PHP is executed by the web server as www-data, and that is not a member of a group with you, the file has to be readable by all. Security of omeka is not Fort Knox.

omeka/themes There we have themes. Each theme is in a directory. You can install a new theme by downloading a theme from the omeka theme web site upload it and then selected it from the admin interface. Let us try this out now.

Please shutdown the computers when you are done. Thank you for your attention!