2.6. Migration workshop: case study analysis

In this workshop we will try to apply what we have learned in this unit to analyse some simple migration processes, and some detail of the required techniques (in the case of network techniques, we will look at these in the units on network administration).

We will consider the following case studies:

2.6.1. Individual migration of a Windows desktop user to a GNU/Linux system

A user considers migrating to GNU/Linux [Ray02b]. Normally, there will first be a period of cohabitation, so that the user can have both systems and use each one for a series of tasks: tasks will continue to be executed in Windows while the user learns about the new system and finds equivalent software or new software that does tasks for which no software was previously available.

Migration for a private user is perhaps one of the most complex processes; we need to offer users alternatives to what they commonly use, so that adaptation is as simple as possible and the user can adapt gradually and with ease to the new system.

A first possibility would be a dual installation [Ban01] [Sko03b] of the original system (Windows) together with the GNU/Linux system.

Example 2-10. Note

Linux Hardware Howto: http://www.tldp.org/HOWTO/HardwareHOWTO/index.html

A first step for a determined machine configuration will consist of checking that our hardware is compatible with Linux [Pri02], either from a list of hardware compatibility or by checking with the manufacturer if new components need to be purchased or the existing ones require a particular configuration. If we are unfamiliar with our hardware, we can check it through the Windows "device administrator" (in the control panel) or using some type of hardware recognition software. At the same time, an advisable method is to use LiveCD-type GNU/Linux distributions, which will allow us to check the functioning of GNU/Linux on our hardware without requiring a physical installation, since the only requirement is the possibility of booting the system from a CD/DVD (in some cases the BIOS configuration may have to be changed for this). There are Live CDs such as Knoppix [Knp] with great support for hardware checks and most GNU/Linux distributions tend to offer a Live CD in order to initially check its functioning (in some cases, Ubuntu [Ubn] for example, the full installation can be done using the same Live CD). In any case, we should mention that checking with a specific Live CD does not mean that there will not be any problems with the final installation, either because the Live CD is not of the same GNU/Linux distribution that we eventually install or because the versions of the system and/or applications will not be the same.

Regarding the physical installation on disk, we will either need to have unpartitioned free disk space or, if we have FAT/32-type partitions, we can liberate space using programs that make it possible to adjust the size of partitions, reducing an existing partition (a previous data backup here is obviously advisable). Currently, most distributions support various disk partitioning and partition reduction schemes, although problems may arise depending on the distribution. If there is not enough space or there are partitions with file systems that present problems (like NTFS with some distributions), we may have to consider buying a new additional hard disk, to use totally or partially for GNU/Linux.

After checking the hardware, we will have to decide on the distribution of the GNU/Linux system that we will use (a possibility we mentioned before is to choose a Live CD that has been satisfactory and to install that distribution). If the user is inexperienced in GNU/Linux or only has basic computer knowledge, it is preferable to choose one of the more user-friendly distributions such as Fedora, Mandriva, SuSe, or similar (we would highlight the ease of Ubuntu in this regard). If we are more knowledgeable or tempted to experiment, we could try a Debian distribution. In the case of commercial distributions, on most occasions the distributions with compatible hardware (business versions like Red Hat and SuSe certify the hardware that they support), are installed perfectly without any problem and basic configurations are made that allow the operating system to be used immediately. During the process, we will have to install the software, which will normally be defined by sets of oriented software: for servers, specific applications or desktop applications, such as office suites, development applications (if we are interested in programming) etc.

Once the system is installed, we have to tackle the issue of sharing data [Gon00] [Kat01], how will we share the data between the two systems? or is it possible to share certain applications? There are various solutions for this:

Example 2-11. Example

A typical case would be the office suite that can be migrated to OpenOffice, which has a high degree of compatibility with Office files and functions fairly similarly, or KOffice (for the KDE desktop), or GNumeric and AbiWord (for Gnome). Or, in the case of image processing, we can take Gimp, with similar functionalities to Photoshop. And numerous multimedia players: Xine, Mplayer (or also a version of RealPlayer). On the Internet we can find numerous lists of equivalent programs between Windows and GNU/Linux.

2.6.2. Migration of a small organisation with Windows systems and a few UNIX

Migration within an organisation (even a small one) has several difficulties: we will have different work environments and heterogeneous software, and, once more, users who are resistant to change.

Example 2-12. Note

For examples of GNU/Linux equivalent applications, see:


http://wiki.linuxquestions.org/wiki/Linux_software_equivalent _to_Windows_software


Now, let's consider an organisation with Windows machines and some UNIX machines as servers or workstations and somewhat "anarchic" users. For example, let's study the following situation: the organisation has a small local network of Windows machines shared by users as equal machines in a Windows workgroup (there are no Windows server domains).

The group is diverse: we have machines with Windows 98, ME, NT, XP, but configured for each user with the software needed for their daily jobs: whether Office, a browser, e-mail reader, or development environments for different language programmers (for example, C, C++, Java).

There are some extra hardware resources available, such as various printers connected to the local network (they accept TCP/IP jobs), which can be used from any point within the organisation. At the same time, there is a shared machine, with a few special resources, such as a scanner, CD recorder and directories shared by the network, where users can leave their own directories with their files for backup processes or to recover scanned images, for example.

We also have several workstations, in this case Sun Microsystem's SPARC, which are running Solaris (commercial UNIX of Sun). These stations are dedicated to development and to some scientific and graphics applications. These machines have NFS services for file sharing and NIS+ for handling the information of users who connect to them and who can do so from any machine in a transparent manner. Some of the machines include specific services; one is the company's web server and another is used as an e-mail server.

We are considering the possibility of migrating to GNU/Linux because of an interest in software development and the particular interest from some users to use this system.

Also, the migration will be made the most of in order to resolve certain problems related to security – some old Windows systems are not the best way of sharing files; we want to restrict use of the printer (the cost in paper and associated costs are high) to more reasonable quotas. At the same time we would like users to have a certain amount of freedom, they will not be obliged to change system, although the suggestion will be made to them. And we will also take advantage in order to purchase new hardware to complement existing hardware, for example if the workstations require additional disk space, which imposes limits on e-mail and user accounts.

Following this small description of our organisation (in other more complex cases it could fill several pages or be a full document analysing the present situation and making future proposals), we can start to consider the possibilities for solving all this:

2.6.3. Migration of a standalone Windows server to a Samba server running GNU/Linux

The basic required process tends to me much more extensive, consult the bibliography for the full steps to be taken.

In this case, the basic required process for a migration from a Windows server that shares files and a printer to a Samba server in a GNU/Linux system.

Thanks to software such as Samba, migration from Windows environments is very flexible and fast and even improves the machine's performance.

Let's suppose a machine belonging to a workgroup GROUP, sharing a printer called PRINTER and with a shared file called DATA, which is no more than the machine's D drive. Several Windows clients access the folder for reading/writing, within a local network with IP 192.168.1.x addresses, where x will be 1 for our Windows server, and the clients will have other values (192.168.x.x networks are often used as addresses to install private internal networks).

As part of our process we will build a Samba server, which is what, as we saw, will allow us to run the SMB/CIFS (server message block / common Internet file system) protocol in GNU/Linux. This protocol allows the file system and the printers to interact through networks on different operating systems. We can mount folders belonging to Windows on the GNU/Linux machines, or part of the GNU/Linux folders on Windows and similarly with each other's printers. The server consists of two daemons (system processes) called smbd and nmbd.

The smbd process manages clients' requests from shared files or printers. The nmbd process manages the machines' names system and resources under the NetBIOS protocol (created by IBM). This protocol is independent from the network used (currently, in NT/2000/XP Microsoft generally uses Netbios over TCP/IP). The nmbd also offers WINS services, which is the name assignment service that is normally run on Windows NT/Server if we have a collection of machines; it is a sort of combination of DNS and DHCP for Windows environments. The process is somewhat complex, but to summarise: when a Windows machine starts up or has a static IP address or dynamic address through a DHCP server and additionally possibly a NetBIOS name (that the user assigns to the machine: in network identification), then the WINS client contacts the server to report its IP; if a network machine subsequently requests the NetBios name, the WINS server is contacted to obtain its IP address and communication is established. The nmbd runs this process on GNU/Linux.

Like any other network service, it should not be run without considering the risk activating it could entail, and how we can minimise this risk. Regarding Samba, we need to be aware of security issues, because we are opening part of our local or network files and printers. We will also have to check the communication restrictions properly in order to prevent access to unwanted users or machines. In this basic example, we will not comment on these issues; in a real case scenario, we would have to examine the security options and only allow access for those we want.

In the migration process, we will first have to configure the GNU/Linux system to support Samba [Woo00], we will need the Samba file systems support in the kernel (smbfs), which is normally already activated. We should add that currently there is additional support in the kernel through the cifs module [Ste07], which as of kernel version 2.6.20 is considered the default method, leaving smbfs as a secondary option. The cifs module offers support for new features related to the CIFS protocol (as an extension of SMB). Through "smbfs" and "cifs" file system names these modules allow us to conduct operations for mounting Windows file systems onto the Windows directory tree (mount -t smbfs or mount -t cifs). Apart from the fact that the kernel support is inclined towards the cifs module, there are some characteristics that may need smbfs support, which means that usually both modules are activated in the kernel. We should also mention the configuration issue, whereas smbfs bases its functioning on the Samba configuration (as we will see in the smb.conf file), the cifs module is given its configuration through the operations (for example, in the mounting process through mount).

In the case of using a Samba server, in addition to the kernel support, we will need to install the associated software packages: we will have to examine what packages related to Samba the distribution includes and install those associated to the functioning of the server. And also, if wanted, those related to Samba as a client, in the event we wish to be clients of Windows machines or to test resources shared with the Windows machines from our GNU/Linux system. In a Debian distribution, these packages are: samba, samba-common, smbclient, smbfs. It may also be interesting to install swat, which is a web-based graphics tool for Samba services administration. For our GNU/Linux Samba server [Woo00] [War03], for the proposed example, we will have to transfer the contents of the previous D disk (where we had our shared file system) from the original machine to the new machine and place its content in a path, like, /home/DATA, whether through a backup copy, FTP transfer, or using Samba as a client to transfer the files.

Regarding the use of GNU/Linux as a Samba client, it is fairly simple. Through the use of client commands for occasional use of the file system:

a) We mount a Windows shared directory (for instance, host being the name of the Windows server), on an existing predefined mounting point:

smbmount //host/carpeta /mnt/windows

b) We will place the access to the Windows folder of the host machine in our local directory, accessing in the directory tree:


c) Next, when it is no longer in use we can dismount the resource with:

smbumount /mnt/windows

If we are not aware of the shared resources, we can obtain a list with:

smbclient -L host

And we can also use smbclient //host/folder, which is a similar program to an FTP client.

In the event of wanting to make the file systems available permanently, or to provide certain special configurations, we can study the use of mount directly (the smbxxxx utilities use it), whether with the smbfs or cifs file systems (supported in the kernel), taking the parameters into account (Windows users/groups authentication or other service parameters) that we will have to provide depending on the case, and of the pre-existing Samba configuration [Ste07].

Example 2-13. Note

Always consult the man pages, or manuals, that come with the software package.

In the case of the Samba server, once we have installed all the Samba software, we will have to configure the server through its configuration file. Depending on the version (or distribution), this file may be in /etc/smb.conf or in /etc/samba/smb.conf. The options shown here belong to a Samba 3.x.x installed on a Debian distribution system. Other versions may have a few minor modifications.

During the installation of the software packages we will normally be asked for data regarding its configuration. In the case of Samba, we will be asked for the workgroup to be served; we will have to place the same group name as in Windows. We will also be asked if we want encrypted passwords (advisable for security reasons, in Windows 9x they were sent in raw text, in a clear case of scarce security and high system vulnerability).

Next we will look at the process of configuring the file smb.conf. This file has three main sections:

1) Global (basic functioning characteristics).

2) Browser (controls what other machines see of our resources).

3) Share (controls what we share).

In this file's extensive manual we can see the available options (man smb.conf). We will edit the file with an editor and see some of the file's lines (characters '#' or ';' at the beginning of a line are comments: If the line contains ';' it is a comment; to enable a line, if it is an optional configuration line we must edit it and remove the ';'):

workgroup = GROUP

This shows the Windows workgroup that the Windows client machines will be members of.

server string = %h server (Samba %v)

We can place a text description of our server. The h and the v that appear are variables of Samba that refer to the host name and version of Samba. For security reasons, it is a good idea to remove the v, since this will inform the exterior what version of Samba we have; if there are known security bugs, this can be used.

hosts allow = 192.168.1

This line may or may not be present, and we can include it to enable what hosts will be served; in this case, all of those in the 192.168.1.x range.

printcap name = /etc/printcap

The printcap file is where GNU/Linux stores the printers' definition, and this is where Samba will look for information about them.

guest account = nobody

This is the guest account. We can create a different account, or just enable access to Samba for the users registered on the GNU/Linux system.

log file = /var/log/samba/log.%m

This line tells us where the Samba log files will be stored. One is stored per client (variable m is the name of the connected client).

encrypt passwords = true

For security reasons it is advisable to use encrypted passwords if we have client machines with Windows 98, NT or above. These passwords are saved in a /etc/samba/smbpasswd file, which is normally generated for users of the Samba installation. Passwords can be changed with the smbpasswd command. There is also an option called UNIX password sync, which allows the change to be simultaneous for both passwords (Samba user and Linux user).

Next, we will jump to the Share Definitions section:


These lines allow access to the users' accounts from the Windows machines. If we don't want this, we will add some ';' to the start of these lines, and when the machines connect they will see the name comment. In principle, writing is disabled, to enable it, you just have to set "yes" as the writable option.

Any sharing of a specific directory (Samba tends to call a group of shared data a partition), we will proceed as shown in the examples that appear (see, for example the definition of sharing the CD-ROM in the lines that start with [cdrom]). In path we will place the access route.

Example 2-14. Example

In our case, for example, we would give the name DATA to the partition on the route /home/DATA, where we had copied the D disk from the original Windows machine and the path where it can be found, in addition to a large group of options that can be modified, users authorised to access them and the way of doing so.

Example 2-15. Note

See: man smb.conf

There is also a profiles definition, that makes it possible to control the profiles of Windows users, in other words, the directory where their Windows desktop configuration is saved, the start up menu etc.

The method is similar for the printers: a partition is made with the printer name (the same one given in GNU/Linux), and in the path we place the queue address associated to the printer (in GNU/Linux we will find it in: /var/spool/samba/PRINTER). And the option printable = yes, if we want jobs to be sent with Samba. And we can also restrict user access (valid users).

Once we have made these changes we will just have to save them and reinitiate Samba so that it can read the new configuration. In Debian:

/etc/init.d/samba restart

Now, our shared directory and the printer through Samba will be available to serve users without them noticing any difference in relation to the previous connections with the Windows server.