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Transcript
Tutorial on Linux Introduction, Installation & Initial Setups Speaker: Faran Javed (BIT-5) Abdul Lateef Khan (BIT-5) Agenda Introduction Planning to Install Installing Red Hat Linux Post Installation Configuration First Steps with Linux Part – I Getting Started Introduction For x86 architecture Free implementation of UNIX Used for Programming Productivity Distributed Computing Telecom & Networking L What is inux ? The core kernel of a free operating system first developed and released to the world by Linus Bendict Torvalds in 1991 What’s Red Hat Linux ? Product of Red Hat Inc. Named after a Cornell university team hat. Objective: Develop release and market an easily managed, and easy to use Linux Distribution Brief History Initiated by Linux Torvalds Initially the little Clone of Unix Version 0.0.1 was never announced Version 0.0.2 announced October 5 1991 Aim was to build a MINIX look-a-like OS for AT 386 machines System Features complete multitasking, multi-user operating system Complete Implementation of the TCP/IP stack and other networking software is provided Variety of File systems supported Ext2 Ext3 XENIX and UNIX System V Microsoft MS-DOS Windows 95 VFAT file systems on a hard drive or floppy. The ISO 9660 CD-ROM file system is also supported. System Features The kernel supports demand-paged, loaded executables. Only those segments of a program which are actually in use are read into memory from disk. unified memory pool for user programs and disk cache. All free memory is used by the cache, which is reduced when running large programs. Executables use dynamically linked, shared libraries System Features To facilitate debugging, the kernel generates core dumps for post-mortem analysis. amount of available memory, Linux also implements disk paging If several instances of a program are running at once, they share physical memory, which reduces overall usage. Software Features Coming Up in Later Slides Preparing To Install L inux Linux Installation Hardware Compatibility http://hardware.redhat.com/hcl/ Disk Space 400 MB – 5 GB depending on minimal, personal, server etc. settings Preparing for the Install Process Most Common Installation Methods CD-ROM NFS From a remotely mounted hard drive containing the red hat Linux software FTP HTTP Hard Drive Partition Preparing to Install from a CD-ROM Just make sure System BIOS is set to BOOT from CD_ROM Partitioning Your Hard Disk Space If Linux is the only OS than we can auto partition Assuming a machine with 20 GB Hard Disk & 256 MB RAM Most basic Scheme Requires a native root partition & a swap partition Typical Partitions For a machine with only Linux on the system the scheme will look like: Hard Drive Partition /dev/hda1 /dev/hda2 Mount Point / swap Size 19.14 GB 512 MB For a machine already having windows: Hard Drive Partition /dev/hda1 /dev/hda2 /dev/hda3 Mount Point /mnt/dos / swap Size 9.74 GB 8.14 GB 512 MB Hosting Parts of the Linux File System on Partitions /home Our users home – will contain our personal files, /opt Directory for additional software packages to be installed /tmp Used as temporary storage for users /usr Holds nearly all software on the red hat system /var Security logs, mails, print spools are under this directory Kickstart Installation Method Automation always saves time Use Red Hats KickStart Configurator A sample ks.cfg file #System Language Lang en-US #Langugae Modules to Install Langsupport en_US Sample File # System Keyboard keyboard us # System mouse Mouse genericps/2 # System time zone Timezone –utc America/NewYork # Root password Rootpw – iscrypted $1$shaldsgfakd3452435gjAJHSGDA/SAD324 The Installation Process Language Selection Keyboard and Mouse configuration Choice of installation type Personal Desktop If new to the world of Linux Workstation If you would like a graphical desktop environment, as well as software development tools Server If you would like your system to function as a Linuxbased server Custom Greatest flexibility Upgrade Installation Process (cont.) Disk partitioning Automatic Partitioning Manual Partitioning ext2, ext3, RAID, swap, vfat etc. Configuring Boot Loader LILO GRUB Network Configuration Firewall Configuration Language & Time Zone Configuration Installation Process (cont.) Authentication setup Package Selection Actual installation Boot Disk creation, VGA and monitor configuration First Steps In Linux Viewing the red hat Linux file system Ls Tree Basic Linux Directories / /bin /boot /dev /etc /home /lib /mnt /opt Proc /root /sbin /tftpboot /tmp /Usr /var The root Directory Essential Commands Boot Loader Files Device Files System Configuration files User home directories Shared libraries usual mount point Add-on software packages Kernel Information Process control Super user System commands mostly root only Network boot support temp files Secondary software file hierarchy Variable data (e.g. logos), spooled files Files in the /etc directory Fstab Inittab Systems printer capabilities database Shells The list of users of the system & their accnt info. Printcap Contains directions and options used when loading kernel modules to enable various types of hardware Passwd The system Initialization table. Defines default run level. Here we can define either to use text or GUI mode. Modules.conf FILE SYSTEM TABLE. A text file listing each hard drive, Floppy drive or other storage attached to your PC. A list of approved shells (command line interfaces) Sysconfig Tree –afx /etc/sysconfig Interact with the kernel Use the proc diractory Vi /proc/meminfo Or use the free command /proc/cpu -- cpu family,type & speed /proc/net – important networking info /proc/net/netstat , /proc/net/route , /proc/net/dev /proc/version – kernel version Remote Login Use SSH – secure shell Linux also supports : Telnet Rlogin Changing user Information Chfn – change finger information Finger – get finger information Accessing Documentation Apropos partition Will display related commands Using the Man pages Man rm Will display manual pages for the rm command Grep Grep alateef /etc/passwd This will search for alateef in /etc/passwd Whereis fdisk Using Environment Variables PWD – current directory USER – declare user name LANG – To set language defaults SHELL – TO declare the name and location of the current shell PATH – set default location of executable files LD_LIBRARY_PATH – location of important software libraries TERM – set the type of terminal in use MACHINE – declare system type, architecture & so on $env /etc/profile Navigating & searching with shell Cd /home/….. Cd .. Whereis Locate Apropos Cat <filename>– contents of file Less <filename> - allows scrolling while reading contents of file name Mv <file1> <file2> Mv <file> <dir> Cp <src> <dst> Rm <file> Rmdir <dir> Grep <string> <file> Compressing & Decompressing Files Bunzip2 - expands a compressed file Bzip2 – compresses or expands files & directories Gunzip Gzip Shar Tar unshar Using Text Editors Ed Emacs Jed Joe Mcedit Pico Sed Vim Vi Gedit Kate Kedit Nedit kwrite Working with vi H,j,k,l – cursor movement Delete character – x Delete line – dd Mode toggle – ESC, Insert (or i) Quit - :q Quit without saving - :q! Save file - :w Text search - / Run a shell command - :sh (use exit to return) Mounting a Drive Compiling a simple C Program Internet Configuration Ethernet Configuration Things you should know IP address Subnet mask It is always 255.0.0.0 for loopback address Broadcast address If you're configuring loopback mode, it is 127.0.0.1 It is equal to your subnet address with 255 replaced as the host address IP address of Gateway IP address of Name server Configuration using system scripts Edit the file /etc/sysconfig/network- scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=static IPADDR=192.168.8.139 NETMASK=255.255.255.0 BROADCAST=192.168.8.255 GATEWAY=192.168.8.1 Edit the file /etc/sysconfig/network NETWORKING=yes HOSTNAME=linux.niit.edu.pk GATEWAY=192.168.8.1 Configuration of Static IP via command line The shell provides two programs for NIC configuration, ifconfig & route ifconfig For configuring the network device interface with certain parameters, such as the IP address, subnetwork mask etc. Remember to bring the interface down & up when modifying Set IP Address ifconfig lo 127.0.0.1 ifconfig eth0 192.168.75.20 netmask 255.255.255.0 Verify Settings ifconfig eth0 route To show and manipulate the IP routing table Add default gateway route add default gw 192.168.1.254 route add –net 192.156.79.0 netmask 255.255.255.0 dev eth0 Important Configuration files /etc/hosts Contains a list of IP addresses and the hostnames they correspond to 127.0.0.1 localhost ENT localhost.localdomain /etc/networks lists the names and addresses of your own and other networks Used by the route command and allows you to specify a network by name instead of by address default 0.0.0.0 # default route - mandatory loopnet 127.0.0.0 # loopback network - mandatory niit-net 202.83.166.171 # Modify for your own network address Important Configuration files /etc/host.conf Specifies how your system resolves hostnames order hosts,bind /etc/resolv.conf Configures the name resolver specifies the address of your nameserver (if any) domains that you want to search by default if a specified hostname is not a fully specified hostname domain niit.edu.pk nameserver 10.10.10.1 Network Configuration for DHCP Edit the file /etc/sysconfig/network- scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=dhcp IPADDR= NETMASK= BROADCAST= GATEWAY= Edit the file /etc/sysconfig/network NETWORKING=yes HOSTNAME= GATEWAY= Basic PPP Configuration for Modems In Windows, modems and other serial devices are named COM1, COM2 etc. In Linux, these are referred as /dev/ttyS0, /dev/ttyS1 At installation time a symbolic link called /dev/modem will be created for the modem KDE graphical tool called “kppp” configures a dialup connection easily Located in /usr/bin/kppp Red Hat requires the root password to be entered each time kppp is executed for security reasons Some distributions allow any user to execute this program such as SuSE Configuring kppp Start kppp Click the Setup button and then click the Device Tab In the Model tab, click Query Modem, it should come up with some results Setting up your ISP Info Accounts button You might need to add the line route add default ppp0 to the field Execute program upon connect: to ensure the default gateway is set to the default gateway from your ISP. Enter your username and password for your ISP and Connect Users Groups & Permissions User Accounts Personal Accounts AAA (Authentication, Authorization, Accounting) Administrative Accounts root Accessed using the su command Daemon accounts e.g., news daemon The passwd File Every account on the system has an entry in the file /etc/passwd username:password:uid:gid:gecos:homedir:shell Username A unique character string, identifying the account Password An encrypted representation of the user's password UID unique integer the system uses to identify the account GID an integer referring to the user's default group, found in the file /etc/group gecos Misc. information like user's real name, office address or phone no. etc. The passwd File homedir user's home directory shell name of the program to run when the user logs in e.g., /bin/bash or /bin/tcsh root:ZxPsI9ZjiVd9Y:0:0:The root of all evil:/root:/bin/bash Shadow Passwords Encrypted passwords in /etc/passwd are potential security risk Instead /etc/shadow is used Contains the real encrypted passwords Readable only by root Contain similar fields but empty or bogus values passwd command -n : sets the minimum number of days between changes -x : the maximum number of days between changes -w : the number of days a warning is issued before a password expires -i the number of days of inactivity between the expiry of a password and the time the account is locked The Group File To logically organize sets of user accounts To allow users to share files within their group or groups Every user is assigned to at least one group The file /etc/group contains a one-line entry for each group on the system groupname:password:gid:members password is an optional encrypted password associated with the group, which allows users not in this group to access the group with the newgrp command members is a comma-separated list of usernames identifying those users who are members of this group but who have a different gid in /etc/passwd root:*:0: bin:*:1:root,daemon users:*:50: bozo:*:51:linus,mdw megabozo:*:52:kibo Creating Accounts Adding an entry to /etc/passwd Creating the user's home directory Setting up the user's default configuration files adduser or useradd Deleting and Disabling Accounts To delete an account remove the user's entry in /etc/passwd remove any references to the user in /etc/group delete the user's home directory any additional files created or owned by the user userdel -r lateef Disabling a user account add an asterisk to the first character of the password field of the /etc/passwd entry kashif:*BjDf5hBysDsii:104:50:lateef Rao:/home/aclark:/bin/bash Modifying User Accounts Simply edit /etc/passwd and /etc/group To change a user's password, use the passwd command Use chown command to change ownership of files chown -R alateef /home/alateef File Ownership and Permissions Permissions refer to the ways in which someone can use a file or directory For files Read permission means you can look at the file's contents Write permission means you can change or delete the file Execute permission means you can run the file as a program File Ownership and Permissions For directories Read permission means you can list the contents of that directory Write permission means you can add or remove files in that directory Execute permission means you can list information about the files in that directory Who gets these permissions? Linux has three levels of permissions Owner Group Other Owners and Groups Each file has an owner and a group Changing the Owner, Group Common mistake when creating a directory under /home for a new user as root chown command changes the owner of a file only root can use chown for changing ownership of a file chgrp command changes the group any user can change the group to another group to which he belongs # chown root /home/lateef/apache.conf # chgrp bin /home/lateef/apache.conf # chown root.bin /home/lateef/apache.conf Changing the Permissions The permissions are also called the file's "mode" The command that changes permissions is chmod Symbolic Mode $ chmod +x header.c $ chmod u-x header.c $ chmod ug+rwx header.c User permission is u, group permission is g, and other is o Changing the Permissions Absolute Mode in terms of bits and octal notation $ chmod 400 header.c $ chmod 555 header.c To set the default mode that is assigned to each file you create umask command $ umask 027 Shutting down the machine Shutdown –h now Or shutdown –h 0 Shutdown –h 18:30 “system is going down for maintenance” Shutdown –r now shutdown –r 0 References http://www.redhat.com/docs/manuals/linu x/RHL-9-Manual/install-guide/ Red Hat Linux 9 Unleashed – Bill Ball & Hoyt Duff