Fedora 15 Release

Fedora is a Linux-based operating system, a suite of software that makes your computer run. You can use the Fedora operating system to replace or to run alongside of other operating systems such as Microsoft Windows™ or Mac OS X™. The Fedora operating system is 100% free of cost for you to enjoy and share. The lastest version of Fedora is Fedora 15.

The following are major features for Fedora 15:

GNOME 3 including the new GNOME 3 shell
KDE 4.6 with the improved Plasma workspace, enhanced core applications, and greater memory efficiency.
Xfce 4.8 with a new panel, Thunar enhancements and more.
Virtualization improvements including Spice support in virt-manager and support for Xen hosts.

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Trick: Backup and Restore MBR

Backing up Master Boot Record (MBR)

The MBR is a 512 byte segment on the very first sector of your hard drive composed of three parts: 1) the boot code which is 446 bytes long, 2) the partiton table which is 64 btyes long, and 3) the boot code signature which is 2 bytes long.

The core of the backup command is dd—which will be familiar to every system administrator, especially to those who intend to clone an entire hard disk. To see all the options type man dd. As we want to back up only the first 512 bytes we need to append some arguments to it. Here is the full command you need (and remember to run it as the root user, su (and sudo for Ubuntu users):

dd if=/dev/hda of=/home/richmondg/mbr_backup bs=512 count=1

Restoring the MBR

You can use a live CD to access your hard drive and read the backup off any removable media such as a USB stick. Here is the command:

dd if=/dev/sda/mbr_backup of=/dev/hda bs=512 count=1

Again, amend sda to read where you saved the MBR and run the command as root. If you wish to kill the MBR altogether, including the partition table, then you can overwrite it with a series of zeros:

dd if=/dev/zero of=/dev/hda bs=512 count=1

If you want to kill the MBR but leave the partition table intact then simply change 512 to 446.

Another way to repair the mbr of your HDD device is install LILO then type (replacing x with the letter of your HDDdevice) :

lilo -M /dev/sdx

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30+ Basic Linux Commands

Here are some basic Linux commands. Some are
well known and some aren't. I am not a Linux
Wizard...far from it...but I am learning some
basic linux commands and thought I would
share some with other newbies so they to can
get more familiar with the terminal command
line. These work on my Mandrake 8.1 system.

xkill Kills a running program
exit Exits the terminal
reboot Reboots the system
halt Shutsdown the computer
startx Starts xwindows from terminal
man man(command)shows help files
info info(command) shows help files
--help (command)--help shows help files
su Allow you to login as Super User

ls "Lists" the contents of the directory
pwd Displays "present working directory"
cd cd (name) change directory TO:(name)
mkdir mkdir (name) Makes new directory
rmdir rmdir (name) Removes directory
clear Clears the terminal window

date Displays current date and time
cal Displays a calander
uptime Displays time since last reboot
df Displays the disk usage on partitions
du Displays disk usage of directory

id Displays your identification to system
groups Displays groups of current user
ulimit -a Displays users limits
uname Displays name of machine logged into
who Displays "who" is logged on the system
w Similar to "who"

wall Sends message to all logged in users
top Displays cpu processes memory etc
ps Displays current running processes

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RPM's Mandrake and RedHat

Check if installed already
rpm -q

To Install the rpm
rpm -ih

To Update a program using an rpm
rpm -Uvh
----------------------

Bored try this:

apropos file List tons of file commands

-----------------------

Many of the commands listed above have
options that can be added to change the
output of that command. To see what they are
do a : man (command) and it will show you the
options.

The command line is hard to learn to use at
first ..... really hard for us converted MS$
users :) but it is worth the effort.

To start a program "like Opera" type the name
at the command prompt:
$ opera

There are many file commands that I didn't
list due to the complexity of them. Read up
on them and you can harness the power of your
computer from the command line!

I have to go read now :)

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Updating the database ubuntu

To update Add/Remove’s database, you need to run “sudo update-app-install”. After that, your .desktop will appear in it’s index as a regular program!

However, by default update-app-install will scan all .desktop files in your system, which on low-end systems can take a while. To help speed that up, you can use the “sudo update-app-install -d ” syntax - point it to the directory where your .desktop is and things will be considerably faster.

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Linux Files and File Permission

Linux files are setup so access to them is controlled. There are three types of access:

1. read
2. write
3. execute

Each file belongs to a specific user and group. Access to the files is controlled by user, group, and what is called other. The term, other, is used to refer to someone who is not the user (owner) of the file, nor is the person a member of the group the file belongs to.When talking about setting permissions for "other" users to use, it is commonly referred to as setting the world execute, read, or write bit since anyone in the world will be able to perform the operation if the permission is set in the other category.

File names can be up to 256 characters long with "-", "_", and "." characters along with letters and numbers.
When a long file listing is done, there are 10 characters that are shown on the left that indicate type and permissions of the file. File permissions are shown according to the following syntax example: drwerwerwe
There are a total of 10 characters in this example, as in all Linux files. The first character indicates the type of file, and the next three indicate read, write, and execute permission for each of the three user types, user, group and other. Since there are three types of permission for three users, there are a total of nine permission bits. The table below shows the syntax:

1	2	3	4	5	6	7	8	9	10
File	User Permissions			Group Permissions			Other Permissions
Type	Read	Write	Execute	Read	Write	Execute	Read	Write	Execute
d	r	w	e	r	w	e	r	w	e

Character 1 is the type of file: - is ordinary, d is directory, l is link.
Characters 2-4 show owner permissions.2=indicates read permission,
3=indicates write permission, 4=indicates execute permission.
Characters 5-7 show group permissions. 5=read, 6=write, 7=execute
Characters 8-10 show permissions for all other users.
8=read, 9=write, 10=execute

There are 5 possible characters in the permission fields. They are:

• r = read - This is only found in the read field.
• w = write - This is only found in the write field.
• x = execute - This is only found in the execute field.
• s = setuid - This is only found in the execute field.
• If there is a "-" in a particular location, there is no permission. This may be found in any field whether read, write, or execute field

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The Differences Between LILO and GRUB

all boot loaders work in a similar way to fulfill a common purpose. But LILO and GRUB do have a number of differences:

LILO has no interactive command interface, whereas GRUB does.

LILO does not support booting from a network, whereas GRUB does.

LILO stores information regarding the location of the operating systems it can to load physically on the MBR. If you change your LILO config file, you have to rewrite the LILO stage one boot loader to the MBR. Compared with GRUB, this is a much more risky option since a misconfigured MBR could leave the system unbootable. With GRUB, if the configuration file is configured incorrectly, it will simply default to the GRUB command-line interface.

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Grub

As with LILO, the steps you will need to perform to use GRUB as your active boot loader depend on whether you are installing the OS fresh or have already installed Linux and are planning on moving to GRUB.

For existing Linux users wanting to migrate to GRUB, get the latest version of GRUB. As the root user, type:

# /boot/grub/grub

This will load up a BASH-like command prompt where you now use the GRUB command:

grub> install (hd1,2)/boot/grub/stage1 (hd1) (hd1,2)/boot/grub/stage2 p (hd1,2)/boot/grub/menu.conf

This command uses the GRUB install command, which requires the location of the stage one image and the location of the MBR (install (hd1,2)/boot/grub/stage1 (hd1)). Also the location of the stage two image ((hd1,2)/boot/grub/stage2) is required. Finally, an optional p (hd1,2)/boot/grub/menu.conf tells GRUB the location of the GUI menu configuration file.

In the previous example, hd1 is my Linux Disk and hd0 is my Windows disk. This will use the current GRUB defaults and splat anything that is currently in the MBR .

Configuring GRUB

GRUB configuration is all done through a configuration file located in /boot/grub/grub.conf. Listing 2 shows an example configuration that relates to my home setup, a dual-booting Linux and Windows machine:

Listing 2. Example grub.conf file

default=0 timeout=10 splashimage=(hd1,2)/grub/splash.xpm.gz password --md5 $1$opeVt0$Y.br.18LyAasRsGdSKLYlp1 title Red Hat Linux password --md5 $1$0peVt0$Y.br.18LyAasRsGdSKLYlp1 root (hd1,2) kernel /vmlinuz-2.4.18-14 ro root=LABEL=/ initrd /initrd-2.4.18-14.img title Windows XP password --md5 $1$0peVt0$Y.br.18LyAasRsGdSKLYlp1 rootnoverify (hd0,0) chainloader +1

The options used in Listing 2 are:

• The default= option signals to GRUB which image to boot from by default after the timeout period. This relates to one of the images in the grub.conf file. 0 is the first specified, 1 is the second specified, etc. If you don't specify this option in the configuration file, it will boot the first image specified in the file.
• timeout= is the number of seconds the boot prompt will wait before automatically loading the default OS, in this case, Red Hat Linux.
• splashimage= is the location of the image to be used as the background for the GRUB GUI.
• The password option specifies the MD5-encrypted password used to gain access to GRUB's interactive boot options. Note this does not stop users loading your defined OS choices; this needs to be set on a per-title basis. To generate an md5 password, run the tool grub-md5-crypt (as root), which comes with GRUB. It will prompt you for the password you want to encrypt. It then will output the MD5-encrypted password. Copy this into your grub.conf after password -md5 but on the same line. Usually this password can be set to the root password, since it is only root who can read the grub.conf file anyway.
• title identifies the specific OS that will be booted from at the user interface at runtime. Unlike with LILO, you can include spaces in this name.
• password is set in the same way as the password above. Do not set this password to the root password if you are planning on sharing this machine with other users.
• The root option tells GRUB where the OS file system actually lives. As you can see, GRUB references the media in a different way than LILO. In our LILO example, /dev/hdb3 is the third partition of the second disk. Grub references this disk as (hd1,2), again the third partition of the second disk (disk 0 being the first disk, partition 0 being the first partition).
• kernel: vmlinuz-X.X.XX-XX is the name of the default boot kernel image within your root directory.
• initrd: initrd-X.X.XX-XX.img is the name of the default initrd file within your root directory.
• title is the same as all other title options.
• password: See other password options.
• The rootnoverify option tells GRUB to not try to vary the root of the OS. This saves load errors if the file system is not a supported by GRUB.
• chainloader +1 tells GRUB to use a chain loader to load this OS, which is required for loading Windows.

You can use many other parameters in the grub.conf file, but the parameters in Listing 2 should get you into a fairly usable state on your machine. For further information on these and other grub.conf parameters, see the manual pages (man grub.conf).

Unlike LILO's configuration file, grub.conf is read at boot time, and the MBR does not need to be refreshed when this is changed.

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LILO = LInux LOader

LInux LOader, or LILO, comes as standard on all distributions of Linux. As one of the older/oldest Linux boot loaders, its continued strong Linux community support has enabled it to evolve over time and stay viable as a usable modern-day boot loader. Some new functionality includes an enhanced user interface and exploitation of new BIOS functions that eliminate the old 1024-cylinder limit.

Although LILO continues to be developed, the basic principles of how LILO works still remain the same.

Making LILO your boot loader

If you already have a Linux distribution installed, you usually get an option to install and configure LILO (and can boot your machine into your new Linux install).

For existing Linux users migrating to LILO, first you have to acquire the latest version of LILO . As the root user, type:

# /sbin/lilo -v -v

This will use the current LILO defaults and splat anything that is currently in the MBR. note that if you want to run Windows and Linux on a single machine, you should install your Windows OS first and then the Linux OS, so that the boot loader you choose in the Linux install won't be written over by the Windows boot loader. Unlike the Linux boot loaders, the majority of Windows boot loaders will not allow you to load Linux. If you've already installed Linux first, don't fret; just create yourself a Linux boot disk so that after you have installed Windows, you can get back into your Linux install and overwrite the MBR.

Configuring LILO

LILO configuration is all done through a configuration file located in /etc/lilo.conf. Listing 1 shows an example configuration, relating to my home machine, for dual booting a Linux and Windows machine. You can visualize how this configuration relates to an actual machine by looking at my basic workstation setup:

• Primary HDD (physical disk 1) with Windows XP installed (initially all there was on the machine). In Linux terms, this HDD is /dev/hda (hd0,0 in GRUB terms).
• Secondary HDD (physical disk 2) with Red Hat Linux installed; the root partition is on the third partition of this hard drive, /dev/hdb3 (hd1,2 in GRUB terms).

Listing 1. Example lilo.conf file

boot=/dev/hda map=/boot/map install=/boot/boot.b prompt timeout=100 compact default=Linux image=/boot/vmlinuz-2.4.18-14 label=Linux root=/dev/hdb3 read-only password=linux other=/dev/hda label=WindowsXP

The options used in Listing 1 are:

• The boot= line tells LILO where to install the boot loader. In the previous example, this will install it to the MBR of first hard disk. You could alternatively install LILO in /dev/hdb3 (the Linux partition in the example), which would then require you to install another boot loader into /dev/hda that points it to the LILO boot loader; then you just let LILO act as a secondary boot loader. In general, /dev/hda is the most common place for your boot loader to reside. You can also make a LILO floppy boot disk by pointing this parameter to the floppy drive, most commonly /dev/fd0.
• map= points to the map file used by LILO internally during bootup. When you install LILO using the /sbin/lilo command, it automatically generates this file, which holds the descriptor table (among other things). My advice is to leave this as it is!
• install= is one of the files used internally by LILO during the boot process. This holds both the primary and secondary parts of the boot loader. A segment of this boot.b file is written to the MBR (the primary part of the boot loader), which then points to the map and subsequently points to the secondary boot loader. Again, leave this as it is!
• prompt= tells LILO to use the user interface (giving you in this example two selections -- Linux and WindowsXP). In addition using the prompt/user interface, you get the option to specify specific parameters for the Linux kernel or others if appropriate. If you do not specify this option in the configuration file, LILO will boot into the default OS with no user interaction and no waiting. (It's worth noting, though, that if you hold the SHIFT key down during boot, you can get the prompt up anyway, which is quite useful if you don't want the average Joe to be exposed to the boot loader).
• timeout= is the number of tenths of a second that the boot prompt will wait before automatically loading the default OS, in this case Linux. If prompt is not specified in the lilo.conf, this parameter is ignored.
• The compact option magically makes the boot process quicker by merging adjacent disk read requests into a single request. It can be a mixed blessing, though, as I've seen a number of posts on forums regarding issues with this option. This option especially useful if you wish to boot from a floppy.
• The default= option tells LILO which image to boot from by default, such as after the timeout period. This relates to a label of one of the images in the lilo.conf file. If you don't specify this option in the configuration file, it will boot the first image specified in the file.
• For each version of Linux you want to make available for users to boot into, you should specify image= and the following three options. The image option specifies the kernel version you wish to boot to.
• label= identifies the different OS you want to boot from at the user interface at runtime. In addition, this label is used for specifying the default OS to boot from. (Note: Avoid spaces in the label name; otherwise, you will get an unexpected error when loading the file.)
• The root= option tells LILO where the OS file system actually lives. In our example, it is /dev/hdb3, which is the third partition of the second disk.
• read-only tells LILO to perform the initial boot to the file system read only. Once the OS is fully booted, it is mounted read-write.
• The password= option allows you to set a password for the specific OS you are booting into. In the example this password is held in the lilo.conf file as readable text, so is easily accessible for all to read. Alternatively if you set password="" you can set the password when the bootloader is installed. These can be set on each of the operating systems you wish to boot from if required (in our example we only set a password on the Linux boot).
• other= acts like a combination of the image and root options, but for operating systems other than Linux. In our example, it tells LILO where to find the Windows OS, which resides on the first disk in the first partition. This will usually be the case if you have installed Windows first, then Linux.
• label= is the same as all other label options.

You can use many other parameters in the lilo.conf file, but the parameters in Listing 1 should get you into a fairly usable state on your machine. For further information on these and other lilo.conf parameters, refer to the manual pages (man lilo.conf). Since lilo.conf is not read at boot time, the MBR needs to be "refreshed" when this is changed. If you do not do this upon rebooting, none of your changes to lilo.conf will be reflected at startup. Like getting LILO into the MBR in the first place, you need to run:

$ /sbin/lilo -v -v

The -v -v flags give you very verbose output. There are a fair number of parameters you can specify when running LILO like we did. See the manual pages for further information (man lilo).

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What is a boot loader?

Most simply, a boot loader loads the operating system. When your machine loads its operating system, the BIOS reads the first 512 bytes of your bootable media (which is known as the master boot record, or MBR). You can store the boot record of only one operating system in a single MBR, so a problem becomes apparent when you require multiple operating systems. Hence the need for more flexible boot loaders.

The master boot record itself holds two things -- either some of or all of the boot loader program and the partition table (which holds information regarding how the rest of the media is split up into partitions). When the BIOS loads, it looks for data stored in the first sector of the hard drive, the MBR; using the data stored in the MBR, the BIOS activates the boot loader.

Due to the very small amount of data the BIOS can access, most boot loaders load in two stages. In the first stage of the boot, the BIOS loads a part of the boot loader known as the initial program loader, or IPL. The IPL interrogates the partition table and subsequently is able to load data wherever it may exist on the various media. This action is used initially to locate the second stage boot loader, which holds the remainder of the loader.

The second stage boot loader is the real meat of the boot loader; many consider it the only real part of the boot loader. This contains the more disk-intensive parts of the loader, such as user interfaces and kernel loaders. These user interfaces can range from a simple command line to the all-singing, all-dancing GUIs.

Boot loaders are usually configured in one of two ways: either as a primary boot loader or as a secondary boot loader. Primary boot loaders are where the first stage of the boot loader is installed on the MBR (per the previous description). Secondary boot loaders are where the first stage of the boot loader is installed onto a bootable partition. A separate boot loader must then be installed into the MBR and configured to pass control to the secondary boot loader.

Many newer Linux boot loaders can be especially useful since they give you varying degrees of interaction, such as advanced GUI and encrypted passwords, along with the ability to load from a selection of operating systems. Thus you can have many operating systems coexisting on the same machine spanning multiple physical disks. This setup has become common because it helps many users reconcile the treasures of valuable datafiles originally generated by their Windows® machines with their shiny new Linux installs. Personally, I think this setup is great; I use a single box for both Linux and Windows.

Over time, boot loaders have been enhanced to include a greater range of functionality for the user. Such functionality and configuration vary from loader to loader, although the basic purpose remains the same.

Two of the more popular boot loaders on Linux: LILO and GRUB.

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