The University of Akron Summit College Business Technology Dept. 2440: 141 Web Site Administration Server Management Instructor: Enoch E. Damson

Web Administrator's View of Server Management The Web server software is a product that works with the operating system The server computer can run more than one software product such as e-mail and FTP With both a LAN and the Web, access control is very important Server Management

Networking Models Two main approaches to networking includes: Microsoft LAN approach to networking Client/server approach to networking Server Management

Microsoft LAN Networking Models Microsoft Windows LAN is configured using one of these two models: Workgroup Domain The model determines how users are organized Server Management

Workgroup Networking Model Treats each computer in the network as an equal, or peer Also called peer-to-peer networking Each computer is a client and a server When you allow others to access resources on your computer, your computer is acting as a server When you access resources on another computer, your computer is acting as a client Appropriate for networks with 10 or less computers Server Management

Workgroup Networking Model… Disadvantages: Most users do not want to administer resources on their computer Need user names and passwords of users who need resources Difficult to keep track of changing passwords Server Management

Domain Networking Model One or more servers centralize control Computers are part of a domain Single, centralized logon Single point of control Users can be given access to resources anywhere in the domain Server Management

Client/Server Networking Model Client represents a program such as a browser or an e-mail client Server has a corresponding program that communicates with the client Client and server communicate using a protocol Web browsers (client) and Web servers use HTTP to communicate Access to servers controlled by a service/daemon Networking in Linux follows the client/server model Each computer has its own database of users/passwords Server Management

Server Users User account – consists of a username and password to identify each user Usually has a home directory for storing files User owns any files created in the home directory Usually a user’s email address (if an email service is provide on the system) Users can log in and upload files if an FTP server is running on the machine Users & Documents

User Accounts Systems administrators need to maintain user accounts by: Creating new user accounts Maintaining the integrity of user accounts Deleting accounts of users not needing access Scripts can be used to speed things up when creating many user accounts Users & Documents

Creating User Accounts Creating an account generally involves: Creating a home directory for a user Setting permissions and groups Installing any login scripts or default directories and files for the user Configuring e-mail if necessary Users & Documents

Maintaining User Accounts With many users, the users’ home directories should all be in a partition or drive separate from the core operating system Keeps the server running smoothly even if users fill available space on the drive Users must be given a quota to keep them from taking up too much space Users & Documents

Authenticating Users Authentication – the process of determining a user’s true identity Process of determining a user's true identity Three basic methods What you know – user name and passwords What you have – entry card Who you are – biometrics Windows authentication could be accomplished using: Kerberos – developed at MIT to allow exchange of private information across a network Certificates – guarantees the identify of an organization or user Server Management

Managing Users and Groups Users need accounts to access resources on a server On a Web server there is a restricted account that is used on behalf of Internet users In a LAN, users with common resource needs are put in a group, and the group is given access to the resource Server Management

Managing Users and Groups… Windows has an account called system It represents the operating system and it has many of the same privileges of the administrator Often needed by server programs Linux typically uses unique accounts for each daemon Server Management

Users and Groups in Windows Local accounts exist on a single computer and can be used to control resources only on that computer Domain accounts can be used to control resources on all the computers that are part of the domain Active Directory (AD) allows domains to be grouped into a forest Server Management

Groups in Windows Domain local groups have members from the same domain Assign permissions to resources in the same domain Global groups have members from the same domain Can be used to assign permissions to resources in any domain Universal groups can have members from any domain Server Management

Users and Groups in Linux Properties of user accounts Item Description User name Logon name of the user Full name The full name of the user or any comment Password The password must be at least six characters Home directory The default is /home/username Group The default is to create a group with the same name as the user Login shell The default is /bin/bash, which determines the characteristic of the shell environment Server Management

File System Permissions Permission allow you to control access to the resources on a computer such as a Web page, a document, or a program In Windows, the NTFS file system is required in order to assign permissions All Linux file systems incorporate permissions Server Management

File System Permissions in Windows Description Full Control Includes all other permissions and allows ownership of the file or folder and change the attributes of a file Modify Allows read, write, and delete Read Read files but cannot execute them Write Write to files or folders Read & Execute Read files and run programs Special Permissions View the contents of a folder Server Management

File System Permissions in Linux Used on Files Used on Directories Read (r) Read a file or copy a file List the contents of a directory Write (w) Write to the file, including deleting the file Create files Execute (x) Execute programs and shell scripts, which are text files containing Linux commands Modify the file permissions Server Management

Linux File Permission Commands The following commands are used for Linux permissions: umask – sets the default file/directory permission chmod – changes the access permissions of a file or directory chgrp – changes the group associated with a file chown – changes the owner associated with a file Server Management

Linux File Permissions Permissions are set for three types of users: User (u) Group (g) Others (o) The three permissions (with their numeric values) are: Read (r) = 4 Write (w) = 2 Execute (x) = 1 Linux permissions may be set using the chmod command in two ways: Numeric values Mnemonics Server Management

Mnemonic Characters for Linux File Permissions Types of users: a  all u  user g  group o  other Permissions: d  directory r  read (4) w  write (2) x  execute (1) -  none (0) Actions: =  assigns permission +  adds permission -  removes permission Use commas to separate assignment units, with no spaces Server Management

Linux File Permission Examples Using umask The umask command uses the numeric values for read (4), write (2) and execute (1) permissions to determine which ones will be unavailable to the category of users (user, group, others) when a file is created Setting default file permissions for all three categories of users (user, group, others) to have all (read, write and execute) permissions umask 000 Setting default file permissions for all three categories of users (user, group, others) to have none of the permissions (read, write and execute) umask 777 Server Management

Setting Linux Default File Permissions Command Default Permissions User Group Other umask 011 rwx rw- umask 233 r-x r-- umask 000 Server Management

Linux File Permission Examples Using chmod Assigning read, write and execute permissions to all users on a file: chmod a=rwx file chmod ugo=rwx file chmod u=rwx,g=rwx,o=rwx file chmod 777 file Assigning read, write permissions to user and execute permission to group and other users on a file: chmod u=rw,go=x file chmod 611 file Adding read, write permissions to all users on a file: chmod ugo+rw file chmod a+rw Adding read, write permissions to user and group; and execute permission to other users on a file: chmod ug+rw,o+x file Removing read, write permissions from all users: chmod a-rw file chmod ugo-rw file Removing write permission from group and other users: chmod go-w file Server Management

Setting Linux File Permissions Using Numeric Values Command Permissions User Group Other chmod 755 myfile rwx r-x chmod 540 myfile r-- --- chmod 744 myfile http://permissions-calculator.org Server Management

Setting Linux File Permissions Using Mnemomics Command Permissions User Group Other chmod u=rwx,go=rx myfile rwx r-x chmod u=rx,g=r,o= myfile r-- --- chmod u=rwx,go=r myfile http://permissions-calculator.org Server Management

Sharing Resources in a Windows Network Shared folders require permissions When comparing share permissions and NTFS permissions, the most restrictive permission takes precedence Permission Description Full Control Allow files to be added, deleted, changed, and read Change Allow existing files to be written to Read Can only read files Server Management

Enforcing Network Policies You can control a number of policies in both Windows and Linux Windows has many more policies but the majority are appropriate for LANs A common policy involves passwords Number of days before change allowed Number of days before change required Server Management

Document Hierarchy Files and directories on Web servers are organized in a file system. File system – determines: Where files are stored on a computer’s hard drive How many letters a filename can contain The security of files stored on the computer There are many different file systems and most modern operating systems can support more than one Users & Documents

Common File Systems Some of the most common file systems are: FAT32 – Microsoft file system NTFS – Windows NT file system UFS – UNIX file system ext3, ext4 – Linux file system HFS – Macintosh hierarchical file system NFS – Network file system Users & Documents