Transcript ITI-481: Unix Administration

ITI-481: Unix Administration
Meeting 2 (Parts 1 and 2)
Meeting 3 (Part 1)
Today’s Agenda
• Software Installation
• Booting and Shutting Down
• Emergency Boot Procedures
Software Installation
• Methods of Installation
– Binary distributions
– Red Hat Package Manager (RPM)
– Compiling from source
• Software installations usually must be done
as root.
Red Hat Package Manager (RPM)
• Generally used for installation and removal of precompiled
software.
• Originally deployed on Linux systems, now available on
other major platforms (most notably, Solaris)
• Installation of operating system and additional software on
Red Hat CD managed through RPMs.
• RPMs that are part of the Red Hat Distribution can be
found on your install CD at:
/mnt/cdrom/RedHat/RPMS
• RPM installations are usually managed by the rpm
command (/bin/rpm)
• As close to “setup” as you can get on UNIX – one
command installs an entire software package.
RPM at the Command Line
• For a list of packages already installed:
rpm –qa
• To install a new package:
rpm –ivh package-file-name
• To upgrade an existing package:
rpm –Uvh package-file-name
• To uninstall a package:
rpm –e package-name
(package name as seen in “rpm –qa”)
RPM at the Command Line (con’t)
• List the files associated with a particular
package:
rpm –ql package-name
Exercise: Using Red Hat Package Manager
• Place your Linux CD in your drive - the files on your CD
can be accessed via the directory /mnt/cdrom.
• The RedHat/RPMS directory on your CDROM contains
many RPM files.
• Install tcpdump off of the Red Hat CD:
> cd /mnt/cdrom/RedHat/RPMS
> rpm –ivh tcpdump-3.4-16.i386.rpm
• Uninstall elm software :
> rpm -e elm-2.5.1-1
• Question: Is pine installed on your system? If so, what is
the version number?
Installing Software from Source
• A source installation the raw computer code
and compiles it into a usable software
program.
• Optimizes software for platform on which it
is compiled.
• Generally provides more installation and
configuration options that using a binary
distribution.
• Requires a C compiler (gcc).
Typical Steps for Installing from Source
• Download source archive.
• Unpack archive
– filename.tar.gz or filename.tgz - use gzip and/or
tar
– filename.Z – use uncompress
– filename.zip – use unzip
• Look at README and/or INSTALL documents for specific
installation steps.
• Usually, you:
– Run configure script if there is one.
– Run make.
– Run make install.
• Key: READ the README and INSTALL files!
Exercise: Installing ssh1 from Source
• Download ssh1.2.27. Additional download
locations can be found at
http://www.ssh.com/products/ssh/download.html.
• From the download directory:
> tar -xvzf ssh-1.2.27.tar.gz
> cd ssh-1.2.27
>./configure
> make
> make install
Where to Find UNIX Software
• Tucows Linux
http://www.linuxberg.com
• Freshmeat
http://www.freshmeat.net/
• Rpmfind.net
http://rpmfind.net/linux/RPM/
• Updates for packages distributed with Red Hat
Linux can be found at any of the Red Hat Mirrors:
http://www.redhat.com/download/mirror.html
Where to Find UNIX Software
• TwoCows – http://www.twocows.com
• SunFreeware –
http://www.sunfreeware.com.
• Download.com – http://www.download.com
The UNIX Boot Process
• The UNIX boot process is unique.
• UNIX is divided into system states called
“run levels”, ranging from level 0 to level 6.
• UNIX Flavors boot differently, but the
general concepts are always the same:
– Bootstrap the system
– Load the “kernel” into memory
– Execute “rc scripts” (startup scripts)
The Linux Boot Process
1. LILO starts and Linux is selected as the
operating system to boot.
2. The Linux kernel is loaded into memory
and then probes system hardware.
3. The init process reads /etc/inittab
and determines whether runlevel 0-6
should be started.
4. rc scripts are executed for the specified
run level to start various services.
Linux Loader (LILO)
• LILO is a boot manager.
• Usually installed in the Master Boot Record
(MBR – a special segment of your hard disk).
• Configuration file is /etc/lilo.conf. If any
changes are made to lilo.conf, /sbin/lilo
needs to be run for the changes to become active.
• For Linux, LILO’s purpose is to identify the
location of the kernel:
/boot/vmlinuz-2.2.12-20
General UNIX System Booting
• Linux is unique, as it uses LILO is a very
interactive bootloading system.
• Administrators rarely interact with the
bootloader on other flavors of UNIX (unless
a special bootloader is present).
The init Process
• init reads /etc/inittab, which designates what
runlevel to start. A runlevel of initdefault is selected
unless otherwise designated.
• A runlevel determines what functionality the system
should be providing. Run levels include:
0 Halt the system
1 Single-user (no networking)
2 Multiuser without NFS
3 Multiuser with NFS
4 Unused
5 Same as 3 but with X11 console
6 Reboot the system
rc Scripts
• init runs /etc/rc.d/rc.sysinit to activate swap partitions and check
consistency of file systems.
• init runs /etc/rc.d/rc with an option designating the runlevel 0-6.
• Runlevel scripts are located in /etc/rc.d/rcX.d (X=runlevel #).
Are used for both startup and shutdown purposes.
• Use the following naming convention:
K or S + Number + Service Name (i.e. S80sendmail)
S is for start. K is for kill. Lower numbers start before higher.
• Startup scripts take two options: start|stop. Scripts with a S are
run with start option. Scripts with a K are run with a stop option.
• Scripts in /etc/rc.d/rcX.d are symbolic links to
/etc/rc.d/init.d.
• /etc/rc.d/rc.local runs last.
Ways of Changing Run Levels
•
•
•
•
/sbin/telinit [0-6] or /sbin/init [0-6]
/sbin/shutdown –h (for halt) –r (for reboot)
/sbin/reboot
/sbin/halt
• At LILO boot prompt:
linux [0-6]
• CTRL-ALT-DELETE
Can be disabled in /etc/inittab.
• Only power-cycle a Linux system as a last resort.
Changing the Default Run Level
• To change the default run level, edit
/etc/inittab – look for the line:
id:3:initdefault:
• After “id:” put the run level number you
wish to use as your default run level.
(usually 3 and 5 are most common options)
• Now when your machine boots, it will
automatically enter that run level.
Useful Keyboard Shortcuts
• Change to text console
CTRL-ALT-[F1-F6]
• Change to X-Windows
CTRL-ALT-F7
• Terminate X-Session
CTRL-ALT-Backspace
Exercise: Changing Runlevels
• As root, type the following:
shutdown –t 30 –h “System Downtime
Beginning”
• Hit the power switch on your machine to turn the system
back on after the shutdown process is complete. NEVER
turn power off without a proper shutdown.
• At the LILO prompt, enter “linux 1.” (Linus only)
• After booting into single-user mode, type:
init 5
Emergency Boot Procedures
•
If system is unable to boot normally, the following
options are available:
– Boot off of your system-specific boot disk - Can be
created during install process or by using mkbootdisk:
> /sbin/mkbootdisk 2.2.12-20
– Boot into single-user mode.
– Boot off of your install floppy or cdrom.
Homework
• Read Chapters 5, 9, 12, and 24 in Linux
Administration: A Beginner’s Guide.