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Special Installations

by Kamran Husain


IN THIS CHAPTER

This chapter covers a variety of topics that basically could not fit in other chapters, nor could they justify a chapter by themselves. We cover these topics briefly and provide locations where you can get more information:

Determining What Tools You Have Installed

The version of Linux on the CD-ROM at the back of this book has the pkgtool utility for you to use. (See Figure 5.1 for this tool's main screen, which includes a list of some of its features.) You see the screen in Figure 5.1 when you install Linux. If you have a color monitor, you will see this in color.

">FIGURE 5.1."> The main screen for pkgtool.

pkgtool can be used to install packages from CD-ROM or mounted floppy disks, or in any mounted directory. You can then view what types of packages are available for your system and remove or add them as necessary.

To view the contents of a package, move the blue highlighted bar down to the View selection and press Enter. You can also type V to go directly to this selection. After you press Enter, you will see another screen, as shown in Figure 5.2.

">FIGURE 5.2."> The View package screen.

Let's look at the contents of the bison package by using the arrow keys to scroll down to bison and then pressing Enter. You are presented with the screen as shown in Figure 5.3. You can scroll up and down in this screen to get the complete listing by using vi movement commands (j or k) or the arrow keys on your keyboard.

">FIGURE 5.3."> The bison View screen.

Now you can decide if you want this package by reading its description. If you feel that you would never use a parser generator, then by all means wipe this package off your disk. (Think twice if you intend to take a compiler class any time in the future.) To delete this package, you have to go back to the main menu. Press Enter to select EXIT. You will return to the view selection screen. Select the Cancel button with the arrow key and press Enter. Then to remove a package, select the Remove option from the pkgtool main menu.

Depending on the speed of your computer, you will most certainly have to wait while you view a message telling you about how many BogoMIPS this is going to take. You can toggle the selection of any packages by using the spacebar. Press Enter when you are done or select the Cancel button if you want to bail out now.

The installpkg Utility

The installpkg utility creates *.tgz packages for distributing Linux files. This program has four modes of operation:

Information about all of the installed packages on your system is stored in /var/adm/packages. Any related script files are stored in /var/adm/scripts.

The removepkg utility is used to remove packages that are listed in the /var/adm/packages directory. There is a -warn option that tells you what files will be removed but are not actually removed yet. Do not use the removepkg utility unless you are absolutely sure that the files in this package are not used elsewhere.

Generating a New Kernel

You will have to install a new kernel if:

To compile a custom kernel for your hardware, follow these steps:

1. If you haven't installed the C compiler and kernel source, do that by running installpkg (discussed above).

2. Use the bootkernel disk you created at the time you installed Linux. At the LILO prompt, enter mount root=/dev/hda1. Ignore any error messages as the system starts up.

3. Change to root.

4. Go to /usr/src/linux.

5. Run the command make config.

6. Choose your drivers and so on.

7. These four commands will build and install the new kernel to work with LILO: 
# make dep



# make clean 



# make zlilo 



# rdev -R /newkernel
CAUTION: Before performing these steps, be sure to read Chapter 56 in its entirety. Compiling a kernel (without proper precautions) that does not match your system configuration can yield your Linux installation unmountable.

Setting the Default Video Mode

You don't have to recompile the kernel to set the default video mode. Just use rdev with the -v switch to set the video mode in the kernel (either on your hard drive or on your boot floppy). For example, to change the kernel in /vmlinuz to prompt for the video mode on bootup, type the following:

rdev -v /vmlinuz -3

To change the kernel on your boot floppy, type

rdev -v /dev/fd0 {video-mode}

These are the valid video-mode options for the kernel: -3 Prompt the user for a response every time

-2 Extended VGA

-1 Normal VGA

The rdev program resides in /sbin. rdev is very handy and also is used to set the root and swap partitions, ramdisk size, and more in a compiled kernel. It means&tm;Ñu don't have to recompb|e the kernel to make these changes. Use rdev -? for a list of options.

Accessing DOS Files

You can always mount the DOS directories and disks to get to DOS files. There is a set of tools called mtools that expedites this procedure. Look at the man pages for a complete description of this handy toolset. The following commands are available for Linux:
mattrib Changes MS-DOS file attribute flags.
mbadblocks Marks bad blocks on an MS-DOS diskette.
mcd Changes MS-DOS directory.
mcopy Copies MS-DOS files to/from UNIX.
mdel Deletes an MS-DOS file.
mdir Displays an MS-DOS directory.
mformat Adds an MS-DOS file system to a low-level formatted diskette.
mlabel Makes an MS-DOS volume label.
mmd Makes an MS-DOS subdirectory.
mmount Mounts an MS-DOS FAT-formatted floppy.
mmove Moves or renames an MS-DOS file.
mrd Removes an MS-DOS subdirectory.
mren Renames an existing MS-DOS file.
mtest Tests and displays configuration information.
mtools A public domain collection of programs that enable UNIX systems to read, write, and manipulate files on an MS-DOS file system (typically a disk). Each program attempts to emulate the MS-DOS equivalent command.
mtype Displays the contents of an MS-DOS file.

Configuring mtools

An entry in the file /etc/mtools contains the following fields: drive, device, fat, cylinders, heads, sectors, and offset. Two examples of entries from /etc/mtools are

A /dev/fd0 12 80 2 15







C /dev/hda1 16 0 0 0

which define the DOS disk in drive A as accessible through the device /dev/fd0, having a 12-bit FAT, 80 cylinders, 2 heads, and 15 sectors per track; DOS disk in drive C is accessible through the device /dev/hda1, has a 16-bit FAT, and its geometry is simply that of the hard disk where it lives. The last three numbers can be zero if you want; this enables mtools to try to figure out the disk's geometry itself, and perhaps to fail. A 12-bit FAT is common for floppies but might occur in small hard-disk partitions. A 16-bit FAT is common for hard disks.

This is an extract of my /etc/mtools file:

A /dev/fd0 12 0 0 0     # 3.5  1.4 Meg (autodetect)



B /dev/fd1 12 0 0 0     # 5.25 1.2 Meg (autodetect)



C /dev/hda1 16 0 0 0    # 1st partition of my Disk

There are two detailed README files in the mtools.n2 distribution. These files treat compiling and using mtools. There is a file README.mtools that treats only using mtools, which is a part of the MCC interim version of Linux.

TIP: If you want to get to the MS-DOS files the hard way, you can use mount -t msdos /dev/hda1 /msdos to mount the partition /dev/hda1 as an MS-DOS file system on the directory /msdos. The directory /msdos, however, must exist before this command can be executed. The caveat to using this approach, however, is that the mount point is not persistent when the system is rebooted. Therein lies the advantage to using mtools--the mount points will remain even after system reboots.

Handling Multiple CD-ROMs

Use the following shell script to mount the CD-ROM drive:

#



# This should be run while logged in as root



echo "Execute:  mount -t iso9660 /dev/cdrom /cdrom"



#



mount -t iso9660 /dev/cdrom /cdrom
CAUTION: Don't pull the CD-ROM out if it's already mounted; use umount /cdrom before swapping disks.

Adding New File Systems

Although this may not seem to be the appropriate place in the book for the topic of creating file systems to expand your files system space, it is. After you have worked with Linux for a while, you will want extra space for all the files you accumulate. If you are not familiar with the way files work in Linux, you might want to familiarize yourself with Chapter 8, "File System."

In most cases, you will want to expand the /usr partition to allow for more programs. Most programs wind up under the /usr partition by default and it's easy to run out of room. A key point to keep in mind is that you do not have to have your entire file structure on the same drive or under the / (root) directory. The major restriction is that /:, /sbin, /bin, /lib, /dev, and /conf have to exist on the root drive for Linux to boot. Any other file systems, including /usr, can be mounted afterward.

Let's start with the example of adding a new physical drive to your system. You can just as easily extend this example to that of creating new partitions on your existing drive and creating a file system on them.

My example here deals with the hard drive on an IDE controller, so my first drive is addressed as/dev/hda and the second as /dev/hdb. If you have a SCSI controller, you will have /dev/sda and/dev/sdb for the first and second drives, respectively.

You have to do the next operation as root, so read the instructions here carefully and be careful when deleting files. The usual check and balance system of confirming permissions on deleting important files does not apply to the superuser.

Create a new partition on your new disk as we did in Chapter 3, "Installing Linux." You can run fdisk /dev/hdb to run fdisk directly on the second partition. As a summary, you will use the n command to create a new partition, specify the size in +Megabytes, and assign a type 83 for Linux native type of partition. After you have created the new partition, it's a good idea to reboot. Most of the documentation I have read on Linux says that it's not necessary, but I am of the old school of thought about being safe and not sorry.

On your return from the reboot, you will create the extended file system with the mke2fs command. The extended file system is the preferred file system because it allows for clean boots without having to worry about a file system check every time you reboot. The syntax for this command to create a file system is

mke2fs -c partition size-in-blocks

Therefore, to create your new file system with 480,000 blocks, you would use this command:

# mke2fs -c /dev/hdb1 4800000

where the /dev/hdb1 is the first partition on drive B, the -c flag checks the newly created blocks for errors, and the size is 480,000 blocks. Be prepared for an onslaught of messages about inodes, blocks, and so forth. This process may take a while, so be patient.

Now you can mount this new file system with the mount command. First, create an empty directory in your root directory, let's call it /data.

# cd /



# mkdir data



# mount -t ext2 /dev/hdb1 /data

The mount command shown above will mount the file system in the second drive as /data. The -t option specifies what type of file system exists on the new partition. You can now copy files into this new /data partition. Now you can use this partition for extra space.

The problem is that this mount is valid only for the duration while your machine is running. If you want this to be mounted automatically at boot time, you should edit the /etc/fstab file and add the following line:

/dev/hdb1   /data ext2  defaults	1	1

The line will cause init, the boot process for Linux, to mount the /dev/hdb1 partition on to the/data directory as an extended file system using the default mount parameters.

Linux Loadable Modules

The Linux kernel (since version 1.2.0) also supports loadable modules. Using loadable modules enables you to build a minimal kernel and add or remove modules to this kernel without requiring a kernel rebuild. A module could be support for a kernel function; for example, the Point-to-Point Protocol (PPP) support module is a loadable module. Only a few loadable modules exist for the Linux kernels at this time, including the sysv, ppp, or slhc (required for ppp) modules.

To see what modules exist in your system, use the lsmod command. To install a module, use the insmod command. Some modules may require other modules. To check the dependencies, use the depmod command. To install a module (and its dependant modules) use the depmod command.

Summary

It's hard to summarize this chapter except to say that this has been a grab-bag of all the things that did not fit anywhere else.

You should now be able to administer the packages on your system, generate a new kernel if necessary, and set the default video mode of your display. This is your first step toward being the superuser you have always dreamed of becoming.

You can still access your old favorite DOS files with the mtools package and configure it to suit your system.

In most of this chapter, though, we covered some topics of installing, configuring, and using Linux. These topics did not fit anywhere else in the book, but are important enough to be included here.