Software Packages Management
#yast –i There will be occasions when a SUSE RPM of a particular package exists but not for the particular SUSE version you are using. If you are running SLES 9 on x86, you should be able to install a binary RPM taken from SUSE 9.1 Professional without any problems, because these two versions are binary compatible. But in many other cases although you may not be able to install the binary RPM, you may be able to take a source package and rebuild it according to your needs. In the simplest case, you would do this (as root): #rpmbuild --clean --rebuild packagename.src.rpm You will then find that in the directory /usr/src/packages/RPMS, in the subdirectory corresponding to your architecture (i586 if you are on x86), there is a brandnew binary RPM package that you can install. Again, you need to have the development tools installed for this to work. Compiling Source Packages You will very often find materials distributed as gzipped tar archives. These are files that will usually have names such as filename.tgz or filename.tar.gz. To extract all the files from this archive, copy it to an empty directory somewhere and use the tar command to unpack it, something like the following example: mkdir unpack Usually, you will then find that a new directory has been created with all the contents of the package inside—if you are lucky, there will be a document there giving you details about how to build the package. Very often (but not always) the way to proceed will be to do the following commands: ./configure You will need to have the development tools installed for this to work.
#rpm –qa grep apache - To check if apache package is installed or not.
The command:
rpm –qpl foreignpackage.rpm
will list the files that foreignpackage.rpm will install. For example,
SUSE does not offer an mpage package. If you examine the mpage package from the Fedora distribution in this way, the result is as follows:
#rpm -qpl mpage-2.5.3-7.i386.rpm
warning: mpage-2.5.3-7.i386.rpm: V3 DSA signature: NOKEY, key ID 4f2a6fd2
/usr/bin/mpage
/usr/share/doc/mpage-2.5.3
/usr/share/doc/mpage-2.5.3/CHANGES
/usr/share/doc/mpage-2.5.3/Copyright
/usr/share/doc/mpage-2.5.3/NEWS
/usr/share/doc/mpage-2.5.3/README
/usr/share/doc/mpage-2.5.3/TODO
/usr/share/man/man1/mpage.1.gz
/usr/share/mpage
/usr/share/mpage/CP850.PC
/usr/share/mpage/ISO+STD+OTH
/usr/share/mpage/ISO-8859.1
/usr/share/mpage/ISO-8859.15
/usr/share/mpage/ISO-Latin.1
/usr/share/mpage/ISO-Latin.2
Through this output you can see that this installation is not going to interfere with any existing files on the system, so you can simply install the package with the command:
#rpm –Uvh mpage-2.5.3-7.i386.rpm
Extracting Files from Packages
The easy way to extract files from packages is with m c (midnight commander), a text-based file manager that has the nice feature that explores inside various types of archives and packages, including RPM packages. So if you start m c in a directory in which there is an RPM package
Working with Source RPMs
cp filename.tgz unpack/
cd unpack
tar zxvf filename.tgz
make
make install
Mounting and Unmounting Filesystems
Mount - To see currently mounted file system
✦ mount 192.168.1.1:/home/bible/ /mnt—Mounts the remote network filesystem /home/bible/ from the machine 192.168.1.1 on the mount point /mnt
✦ mount /dev/hda3 /usr/local—Mounts the disk partition /dev/hda3 on the mount Point /usr/local
✦ umount /mnt—Unmounts whatever is mounted on the mount point /mnt
Users and Groups Administration
You can also create a new user from the command line with the command useradd. The equivalent command would be:
In a similar way, you can create or modify groups through YaST, and there are equivalent
command-line commands called groupadd (to add groups) and groupmod (to
modify existing groups
✦ rwx means permission to read, write, and execute
✦ r-- means permission to read but not to write or execute
✦ r-x means permission to read and execute but not to write
-rw-r--r-- 1 roger users 432686 2004-0 5-17 20:33 screenshot1.png
-r-------- 1 roger users 0 2004-0 5-17 21:07 afile
ls -l /bin/mount
-rwsr-xr-x 1 root root 87296 2004-0 4-06 14:17 /bin/mount
lrwxrwxrwx 1 roger users 8 2004-0 5-17 22:19 alink -> file.bz2
Note the lin the first position: This is a symbolic link to file.bz2 in the same directory.
You can change the ownership of a file with the command chown. If you are logged in as root, you can issue a command like this:
#chown harpo:users file.txt
This changes the ownership of the file file.txt to the user harpo and the group users.
To change the ownership of a directory and everything in it, you can use the command with the -R (recursive) option, like this: chown -R harpo:users /home/harpo/some_directory/
The chmod command is used to change file permissions. You can use chmod with both the numerical and the rwx notation we discussed earlier in the chapter. Again, this is easiest to follow by looking at a few examples:
✦ chmod u+x afile—Adds execute permissions for the owner of the file
✦ chmod g+r afile—Adds read permissions for the group owning the file
✦ chmod o-r afile—Removes read permission for others
✦ chmod a+w afile—Adds write permissions for all
✦ chmod 644 afile—Changes the permissions to 644 (owner can read and write; group members and others can only read)
✦ chmod 755 afile—Changes the permissions to 755 (owner can read, write and execute; group members and others can only read and execute)
If you use chmod with the rwx notation, u means the owner, g means the group, o means others, and a means all. In addition, + means add permissions, and - means remove permissions, while r, w, and x still represent read, write, and execute, respectively. When setting permissions, you can see the translation between the two notations by executing the chmod command with the -v (verbose) option. For example:
chmod -v 755 afile
mode of `afile’ changed to 0755 (rwxr-xr-x)
chmod -v 200 afile
mode of `afile’ changed to 0200 (-w-------)
Using umask
When a user creates a file, it is created with certain permissions. You can create an empty file with the touch command:
If you then list the file, you will see something like this:
#ls -l newfile
Searching Files with grep, find and locate
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✦ grep sample /etc/exports—Looks for all lines in the file /etc/exports that include the string bible
✦ tail -100 /var/log/apache/access.loggrep 404—Looks for the string 404, the web server’s “file not found” code, in the last hundred lines of the web server log
✦ tail -100 /var/log/apache/access.loggrep -v googlebot—Looks in the last 100 lines of the web server log for lines that don’t indicate accesses by the Google search robot
✦ grep -v ^# /etc/apache2/httpd.conf—Looks for all lines that are not commented out in the main Apache configuration file .
Finding Files with find and locate
✦ find .-name *.rpm—Finds RPM packages in the current directory
✦ find .grep page—Finds files in the current directory and its subdirectories with the string page in their names
✦ locate traceroute—Finds files with names including the string traceroute anywhere on the system
Links to Files or Directories
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In Linux, you can use the ln (link) command to make links to a file or directory. A file can have any number of so-called “hard” links to it. Effectively, these are alternative names for the file. So if you create a file called afile, and make a link to it called bfile, there are now two names for the same file. If you edit afile, the changes you’ve made will be in bfile. But if you delete afile, bfile will still exist; it will disappear only when there are no links left to it. Hard links can be made only on the same filesystem—you can’t create a hard link to a file on another partition because the link operates at the filesystem level, referring to the actual filesystem data structure that holds information about the file. You can create a hard link only to a file, not to
a directory.
You can also create a symbolic link to a file. A symbolic link is a special kind of file that redirects any usage of the link to the original file. This is somewhat similar to the use of “shortcuts” in Windows. You can also create symbolic links to directories, which can be very useful if you frequently use a subdirectory that is hidden several levels deep below your home directory. In the last example that follows, you will end up with a symbolic link called useful in the current directory. Thus, the command cd useful will have the same effect as cd docs/linux/suse/useful.
✦ ln afile bfile—Makes a “hard” link to afile called bfile
✦ ln -s afile linkfile—Makes a symbolic link to afile called linkfile
✦ ln -s docs/linux/suse/useful—Makes a symbolic link to the named directory in the current directory
setting and unsetting Environment Variables
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Environment variables can be set in a number of places:
✦ System-wide configuration files such as those located in /etc/profile, /etc/profile.local, and the directory /etc/profile.d on a Linux system. These are system-wide files that are executed to help initialize your working environment each time you log in.
✦ System-wide configuration files such as /etc/bashrc. These are typically executed by a user’s personalized bash configuration file each time that you start a new shell and set system-wide shell configuration variables.
✦ User-specific configuration files such as .bashrc that are read each time you start a new shell.
✦ Within shell scripts for use within those scripts or to be exported back to the command-line environment.
✦ From the command line for your convenience or within shell functions executed by the shell.
Environment variables that you want to make available to all subsequent shells are made available to the parent shell using the export command. For example, suppose that you want to set an environment variable named SAVEME to the name of the current directory so that you can remember it. If the current directory is /home/wvh, you can set the SAVEME environment variable to this directory with the following command:
export SAVEME=/home/wvh
One common task involving environment variables is to add a new directory to the column-separated value of the PATH environment variable so that your shell looks in that directory for executables. For example, suppose that you’ve just installed the popular Linux Firefox browser on your system. Firefox is typically installed in the directory /usr/local/firefox, and the binary program that you actually execute to run the browser is /usr/local/firefox/firefox. You can always execute Firefox by typing the full path of the firefox command, but that’s a bit tedious. A
better solution is to add the directory /usr/local/firefox to the value of your PATH environment variable (generally referred to as “adding it to your path”). You can do this within the current shell by executing the following command:
export PATH=$PATH:/usr/local/firefox
After typing this command, you can execute the firefox command from that shellby simply typing firefox and pressing Return.
you can unset it at any time using the unset command. The unset command removes the environment variable and its associated value from the shell in which you execute it.
Boot Option while Installation Suse
What are the different kind fo Boot options while Installation.
Boot from Hard Disk—This is the default setting if you do not interact with the boot sequence. It’s the default because your system automatically reboots as part of the installation process to load the kernel that is installed on your hard drive during the initial phases of the installation process. If you forget to remove the installation media, the system will still boot off the hard disk and the install routine can continue.
✦ Installation—This is the standard option that most users should select. It will boot from the CD and start the install routine (YaST). We discuss the rest of the process in the remainder of this chapter.
✦ Installation — ACPI Disabled—Advanced Configuration and Power Interface
(ACPI) is a feature of most new processors that controls power management and the way interrupts are handled by the system hardware. You should select this option if you encounter problems during the installation process, such as if your computer system goes to sleep (blanks the screen and powers down the drives) and if pressing the appropriate keystroke does not wake it up again.
✦ Installation — Safe Settings—As with the ACPI Disabled installation method,
this turns off some of the features of the kernel that can cause problems with buggy or old system hardware. You should select this option if you encounter problems during installation, and they do not seem related to power management.
✦ Rescue System—The Rescue System enables you to correct system problems, such as disk corruption or lost passwords, by booting from the installation media and subsequently correcting system problems. The Rescue System is quite a feature-rich system that you can use to load and edit filesystems, as well as change the settings of an installed system.
✦ Memory Test—SUSE has been very kind and integrated a memory test suite in the system boot menu. The memory test will run long and exhaustive tests on your system’s memory and warn you of any anomalies that it encounters on the way. We have used this a few times with systems that don’t quite seem to be running as we expect, and it has been able to tell us that a DIMM (Dual In-Line Memory Module) has indeed failed.
Suse Linux Interview Questions and Answers
1)I Forgot My Root Password! What Do I Do?”
Ans - Boot into singleuser mode, which you can accomplish by rebooting your machine. When you see the blue screen with the words “Press any key to enter the menu,” press a key. At the GRUB boot screen, press E, which takes you to a configuration file. Use the arrow keys to go to the line starting with kernel, and press E again
to edit that line. At the end of the line, add the word single, press Enter to
put the change into place, and then press B to boot the machine. Type passwd and then enter the new password twice as directed. When you finish, type exit and then boot the machine normally.
