Partitioning Your Disk for Red Hat Linux

The Current Disk Partitions Section

Each line in the Current Disk Partitions section represents a disk partition. In this example (Figure 14-15), there are Linux existing partitions.

Note the scroll bar to the right, which indicates that there may be more partitions than can be displayed at one time. If you use the Up and Down arrow keys, you can see if there are any additional partitions. Each line in this section has five different fields:

• Mount Point -- Indicates where the partition will be mounted when Red Hat Linux is installed (such as /, /boot, or swap).

• Device -- Displays specific hard drive and partition information.

• Requested -- Shows the partition's initial size.

• Actual -- Shows the partition's current size.

• Type -- Shows the partition's type.

As you scroll through the Current Disk Partitions section, you might see an Unallocated Requested Partitions title bar, followed by one or more partitions. These are partitions that have been requested but, for one reason or another, have not been allocated. A common reason for having an unallocated partition is a lack of sufficient free space for the partition. In any case, the reason the partition remains unallocated will be displayed after the partition's mount point.

The Drive Summaries Section

Each line in the Drive Summaries section represents a hard disk on your system. Each line has the following fields:

• Drive -- Shows the hard disk's device name.

• Geom [C/H/S] -- Shows the hard disk's geometry. The geometry consists of three numbers representing the number of cylinders, heads and sectors as reported by the hard disk.

• Total -- Shows the total available space on the hard disk.

• Used -- Shows how much of the hard disk's space is currently allocated to partitions.

• Free -- Shows how much of the hard disk's space is still unallocated.

• Bar Graph -- Presents a visual representation of the space currently used on the hard disk. The more pound signs there are between the square braces, the less free space there is. In Figure 14-15, the bar graph shows no free space.

	Please Note
	The Drive Summaries section is displayed only to indicate your computer's disk configuration. It is not meant to be used as a means of specifying the target hard drive for a given partition. This is described more completely in the section called Adding a Partition.

Disk Druid's Buttons

These buttons control Disk Druid's actions. They are used to add and delete partitions, and to change partition attributes. In addition, there are buttons that are used to accept the changes you've made, or to exit Disk Druid entirely. Let's take a look at each button in order.

• Add -- Request a new partition. Selecting this button causes a dialog box to appear containing fields that must be filled in.

• Edit -- Modify the mount point of the partition currently highlighted in the Current Disk Partitions section. Selecting this button will cause a dialog box to appear allowing you to change the name of the mount point.

• Delete -- Delete the partition currently highlighted in the Current Disk Partitions section. Selecting this button will cause a dialog box to appear asking you to confirm the deletion.

• OK -- Confirm that changes made to your system's partitions to be written to disk. You will be asked to confirm the changes before Disk Druid rewrites your hard disk partition table(s). In addition, any mount points you've defined are passed to the installation program, and will eventually be used by your Red Hat Linux system to define the filesystem layout.

• Back -- Abort without saving any changes you've made. When this button is selected, the installation program will take you back to the previous screen, so you can start over.

Handy Function Keys

Use the F5 (Reset) function key to discard all changes you may have made while in Disk Druid, and return the list of partitions to those read from the partition table(s) on your hard disk(s). When selected, you'll be asked to confirm whether you want to discard the changes. Note that any mount points you've specified will be lost, and will need to be reentered.

	Please Note
	You will need to dedicate at least one partition to Red Hat Linux, and optionally more. This is discussed more completely in the section called How Many Partitions? in Appendix B.

Adding a Partition

To add a new partition, select the Add button and press Space or Enter. The Edit New Partition dialog (Figure 14-16) appears.

The screen contains the following fields:

• Mount Point -- Highlight this field and enter the partition's mount point. For example, if this partition should be the root partition, enter /; enter /usr for the /usr partition, and so on.

• Size (Megs) -- In this field, enter the size (in megabytes) of the partition. Note that this field starts with a "1" in it, meaning that unless you change it, you'll end up with a 1 MB partition. Delete it using the Backspace key, and enter the desired partition size.

• Grow to fill disk? -- This check box indicates whether the size you entered in the previous field is to be considered the partition's exact size, or its minimum size. Press Space to select this option. When selected, the partition will grow to fill all available space on the hard disk. In this case, the partition's size will expand and contract as other partitions are modified. If you make more than one partition growable, the partitions will compete for the available free space on the disk.

• Type -- This field contains a list of different partition types. Select the appropriate partition type by using the Up and Down arrow keys.

• Allowable Drives -- This field contains a list of the hard disks installed on your system, with a check box for each. If a hard disk's box is checked, then this partition may be created on that hard disk. By using different check box settings, you can direct Disk Druid to place partitions as you see fit, or let Disk Druid decide where partitions should go.

• OK -- Select this button and press Space when you are satisfied with the partition's settings, and wish to create it.

• Cancel -- Select this button and press Space when you don't want to create the partition.

Recommended Partitioning Scheme

Unless you have a reason for doing otherwise, we recommend that you create the following partitions:

• A swap partition (at least 16MB) -- Swap partitions are used to support virtual memory. In other words, data is written to a swap partition when there is not enough RAM to store the data your system is processing. If your computer has 16MB of RAM or less, you must create a swap partition. Even if you have more memory, a swap partition is still recommended. The minimum size of your swap partition should be equal to your computer's RAM, or 16MB (whichever is larger). In Disk Druid, the partition field for swap should look similar to:

  <Swap> hda2 125M 125M Linux swap

• A /boot partition (16MB, maximum) -- The partition mounted on /boot contains the operating system kernel (which allows your system to boot Red Hat Linux), along with files used during the bootstrap process. Due to the limitations of most PC BIOSes, creating a small partition to hold these files is a good idea. This partition should be no larger than 16MB. In Disk Druid, the partition field for /boot should look similar to:

  /boot hda1 16M 19M Linux native

• A root partition (900MB-1.7GB) -- This is where "/" (the root directory) resides. In this setup, all files (except those stored in /boot) reside on the root partition. A 850MB root partition will permit the equivalent of a workstation-class installation (with very little free space), while a 1.7GB root partition will let you install every package. In Disk Druid, the partition field for / should look similar to:

  / hda2 900M 3669M Linux native

Problems When Adding a Partition

	Please Note
	If you are having problems adding a partition, turn to Appendix B, An Introduction to Disk Partitions, to find a solution.

If you attempt to add a partition and Disk Druid can't carry out your request, you'll see a dialog box listing any partitions that are currently unallocated, along with the reason they could not be allocated, as in Figure 14-17. Select the OK button, and press Space to continue. Note that the unallocated partition(s) are also displayed on Disk Druid's main screen (though you may have to scroll the Current Disk Partitions section to see them).

Editing a Partition

To change a partition's mount point, highlight the partition in the Current Disk Partitions section, select the Edit button, and press Space. The Edit Partition dialog is similar to the one shown in Figure 14-16. The difference here is that all fields except the mount point are read-only. To modify any other value, delete the partition and add it again with the new values.

Deleting a Partition

To delete a partition, highlight the partition in the Current Disk Partitions section, select the Delete button, and press Space. You will be asked to confirm the deletion.

When You're Finished

Once you've configured your partitions and entered your mount points, you screen should look something like Figure 14-19.

Choose Partitions to Format Dialog

Next, select which partitions you want to format (Figure 14-20). You must format all newly created partitions and other partitions that contain old data (assuming they don't contain data you wish to keep).

	Caution
	If partitions such as /home or /usr/local already exist and contain data you wish to keep, do not select these for formatting.

When you have selected the partitions to format, press Space. If you wish to check for bad blocks while formatting each filesystem (recommended for those with older disk drives), select Check for bad blocks during format. Select OK, and press Space.

	Please Note
	Selecting check for bad blocks may dramatically increase your total installation time. Since most newer hard drives are quite large in size, checking for bad blocks may take a while depending on the size of your hard drive.

Using fdisk

If you chose a custom-class installation, you also chose which disk partitioning application to use. This section only applies if you opted to use fdisk.

Once you've selected fdisk, you'll be presented with the Partition Disks dialog box (Figure 14-21). In this box is a list of every disk on your computer.

Using Tab, and the Up and Down arrow keys, highlight the disk you'd like to partition, select Edit, and press Space.

You will then enter fdisk and can partition the disk you selected. Repeat this process for each disk you want to partition. When you're finished, select Done.

An Overview of fdisk

fdisk includes online help which is terse but useful. Here are a few tips:

• The command for help is m.

• To list the current partition table, use the p command (see Figure 14-22).

• To add a new partition, use n.

• Linux fdisk creates partitions of type Linux native by default. When you create a swap partition, don't forget to change it to type Linux swap using the t command. The value for the Linux swap type is 82. For other partition types, use the l command to see a list of partition types and values.

• Linux allows up to four (4) partitions on one disk. If you wish to create more than that, one (and only one) of the four may be an extended partition, which acts as a container for one or more logical partitions. Since it acts as a container, the extended partition must be at least as large as the total size of all the logical partitions it is to contain.

• It's a good idea to write down which partitions (e.g., /dev/hda2) are meant for which filesystems (e.g., /usr) as you create each one.

	Please Note
	None of the changes you make take effect until you save them and exit fdisk using the w command. You can quit fdisk at any time without saving changes by using the q command.

Figure 14-22. Sample Output from fdisk