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2440: 141 Web Site Administration Server Management Instructor: Enoch E. Damson

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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 Management2

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Networking Models Two main approaches to networking includes: Microsoft LAN approach to networking Client/server approach to networking Server Management3

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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 Management4

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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 Management5

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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 Management6

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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 Management7

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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 Management8

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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 users 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 & Documents9

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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 & Documents10

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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 & Documents11

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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 & Documents12

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Authenticating Users Authentication the process of determining a users 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 Management13

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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 Management14

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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 Management15

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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 Management16

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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 Can be used to assign permissions to resources in any domain Server Management17

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Users and Groups in Linux Properties of user accounts ItemDescription User nameLogon name of the user Full nameThe full name of the user or any comment PasswordThe password must be at least six characters Home directoryThe default is /home/username GroupThe default is to create a group with the same name as the user Login shellThe default is /bin/bash, which determines the characteristic of the shell environment Server Management18

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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 Management19

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File System Permissions in Windows PermissionDescription Full ControlIncludes all other permissions and allows ownership of the file or folder and change the attributes of a file ModifyAllows read, write, and delete ReadRead files but cannot execute them WriteWrite to files or folders Read & ExecuteRead files and run programs Special PermissionsView the contents of a folder Server Management20

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File System Permissions in Linux PermissionUsed on FilesUsed on Directories Read (r)Read a file or copy a fileList 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 Management21

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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 Management22

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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 Management23

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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 Management24

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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 Management25

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Setting Linux Default File Permissions CommandDefault Permissions UserGroupOther umask 011 rwxrw- umask 233 r-xr-- umask 000 rwx Server Management26

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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 Management27

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Setting Linux File Permissions Using Numeric Values CommandPermissions UserGroupOther chmod 755 myfile rwxr-x chmod 540 myfile r-xr----- chmod 744 myfile rwxr-- Server Management28 http://permissions-calculator.org

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Setting Linux File Permissions Using Mnemomics CommandPermissions UserGroupOther chmod u=rwx,go=rx myfile rwxr-x chmod u=rx,g=r,o= myfile r-xr----- chmod u=rwx,go=r myfile rwxr-- Server Management29 http://permissions-calculator.org

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Sharing Resources in a Windows Network Shared folders require permissions When comparing share permissions and NTFS permissions, the most restrictive permission takes precedence PermissionDescription Full ControlAllow files to be added, deleted, changed, and read ChangeAllow existing files to be written to ReadCan only read files Server Management30

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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 Management31

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Document Hierarchy Files and directories on Web servers are organized in a file system. File system determines: Where files are stored on a computers 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 & Documents32

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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 & Documents33