10.0 2010-07-19
Introduction to Block Devices Partitions and Slices

Although it is theoretically possible to use a full disk to house your Linux system, this is almost never done in practice. Instead, full disk block devices are split up in smaller, more manageable block devices. On most systems, these are called partitions. Other architectures use a similar technique, called slices.

Designing a Partitioning Scheme How Many and How Big?

The number of partitions is highly dependent on your environment. For instance, if you have lots of users, you will most likely want to have your /home separate as it increases security and makes backups easier. If you are installing Gentoo to perform as a mailserver, your /var should be separate as all mails are stored inside /var. A good choice of filesystem will then maximise your performance. Gameservers will have a separate /opt as most gaming servers are installed there. The reason is similar for /home: security and backups. You will definitely want to keep /usr big: not only will it contain the majority of applications, the Portage tree alone takes around 500 Mbyte excluding the various sources that are stored in it.

As you can see, it very much depends on what you want to achieve. Separate partitions or volumes have the following advantages:

  • You can choose the best performing filesystem for each partition or volume
  • Your entire system cannot run out of free space if one defunct tool is continuously writing files to a partition or volume
  • If necessary, file system checks are reduced in time, as multiple checks can be done in parallel (although this advantage is more with multiple disks than it is with multiple partitions)
  • Security can be enhanced by mounting some partitions or volumes read-only, nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.

However, multiple partitions have one big disadvantage: if not configured properly, you might result in having a system with lots of free space on one partition and none on another. There is also a 15-partition limit for SCSI and SATA.

Using fdisk on HPPA to Partition your Disk

Use fdisk to create the partitions you want: 

# fdisk /dev/sda

HPPA machines use the PC standard DOS partition tables. To create a new DOS partition table, simply use the o command. 

# fdisk /dev/sda

Command (m for help): o
Building a new DOS disklabel.

PALO (the HPPA bootloader) needs a special partition to work. You have to create a partition of at least 16MB at the beginning of your disk. The partition type must be of type f0 (Linux/PA-RISC boot).

If you ignore this and continue without a special PALO partition, your system will stop loving you and fail to start. Also, if your disk is larger than 2GB, make sure that the boot partition is in the first 2GB of your disk. PALO is unable to read a kernel after the 2GB limit. 
# cat /etc/fstab
/dev/sda2    /boot   ext3    noauto,noatime   1 1
/dev/sda3    none    swap    sw               0 0
/dev/sda4    /       ext3    noatime          0 0

# fdisk /dev/sda

Command (m for help): p

Disk /dev/sda: 4294 MB, 4294816768 bytes
133 heads, 62 sectors/track, 1017 cylinders
Units = cylinders of 8246 * 512 = 4221952 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1           8       32953   f0  Linux/PA-RISC boot
/dev/sda2               9          20       49476   83  Linux
/dev/sda3              21          70      206150   82  Linux swap
/dev/sda4              71        1017     3904481   83  Linux

Now that your partitions are created, you can continue with Creating Filesystems.

Creating Filesystems Introduction

Now that your partitions are created, it is time to place a filesystem on them. If you don't care about what filesystem to choose and are happy with what we use as default in this handbook, continue with Applying a Filesystem to a Partition. Otherwise read on to learn about the available filesystems...

Applying a Filesystem to a Partition

To create a filesystem on a partition or volume, there are tools available for each possible filesystem:

ext2mke2fsext3mke2fs -jreiserfsmkreiserfsxfsmkfs.xfsjfsmkfs.jfs
Filesystem Creation Command

For instance, to have the boot partition (/dev/sda2 in our example) in ext2 and the root partition (/dev/sda4 in our example) in ext3 (as in our example), you would use: 

# mke2fs /dev/sda2
# mke2fs -j /dev/sda4

Now create the filesystems on your newly created partitions (or logical volumes).

Activating the Swap Partition

mkswap is the command that is used to initialize swap partitions: 

# mkswap /dev/sda3

To activate the swap partition, use swapon: 

# swapon /dev/sda3

Create and activate the swap with the commands mentioned above.

Mounting

Now that your partitions are initialized and are housing a filesystem, it is time to mount those partitions. Use the mount command. Don't forget to create the necessary mount directories for every partition you created. As an example we mount the root and boot partition: 

# mount /dev/sda4 /mnt/gentoo
# mkdir /mnt/gentoo/boot
# mount /dev/sda2 /mnt/gentoo/boot
If you want your /tmp to reside on a separate partition, be sure to change its permissions after mounting: chmod 1777 /mnt/gentoo/tmp. This also holds for /var/tmp.

We will also have to mount the proc filesystem (a virtual interface with the kernel) on /proc. But first we will need to place our files on the partitions.

Continue with Installing the Gentoo Installation Files.