2.4. Creating a New Partition

Like most other operating systems, LFS is usually installed on a dedicated partition. The recommended approach to building an LFS system is to use an available empty partition or, if you have enough unpartitioned space, to create one.

A minimal system requires a partition of around 10 gigabytes (GB). This is enough to store all the source tarballs and compile the packages. However, if the LFS system is intended to be the primary Linux system, additional software will probably be installed which will require additional space. A 30 GB partition is a reasonable size to provide for growth. The LFS system itself will not take up this much room. A large portion of this requirement is to provide sufficient free temporary storage as well as for adding additional capabilities after LFS is complete. Additionally, compiling packages can require a lot of disk space which will be reclaimed after the package is installed.

Because there is not always enough Random Access Memory (RAM) available for compilation processes, it is a good idea to use a small disk partition as swap space. This is used by the kernel to store seldom-used data and leave more memory available for active processes. The swap partition for an LFS system can be the same as the one used by the host system, in which case it is not necessary to create another one.

Start a disk partitioning program such as cfdisk or fdisk with a command line option naming the hard disk on which the new partition will be created—for example /dev/sda for the primary disk drive. Create a Linux native partition and a swap partition, if needed. Please refer to cfdisk(8) or fdisk(8) if you do not yet know how to use the programs.

Note

For experienced users, other partitioning schemes are possible. The new LFS system can be on a software RAID array or an LVM logical volume. However, some of these options require an initramfs, which is an advanced topic. These partitioning methodologies are not recommended for first time LFS users.

Remember the designation of the new partition (e.g., sda5). This book will refer to this as the LFS partition. Also remember the designation of the swap partition. These names will be needed later for the /etc/fstab file.

2.4.1. Other Partition Issues

Requests for advice on system partitioning are often posted on the LFS mailing lists. This is a highly subjective topic. The default for most distributions is to use the entire drive with the exception of one small swap partition. This is not optimal for LFS for several reasons. It reduces flexibility, makes sharing of data across multiple distributions or LFS builds more difficult, makes backups more time consuming, and can waste disk space through inefficient allocation of file system structures.

2.4.1.1. The Root Partition

A root LFS partition (not to be confused with the /root directory) of twenty gigabytes is a good compromise for most systems. It provides enough space to build LFS and most of BLFS, but is small enough so that multiple partitions can be easily created for experimentation.

2.4.1.2. The Swap Partition

Most distributions automatically create a swap partition. Generally the recommended size of the swap partition is about twice the amount of physical RAM, however this is rarely needed. If disk space is limited, hold the swap partition to two gigabytes and monitor the amount of disk swapping.

If you want to use the hibernation feature (suspend-to-disk) of Linux, it writes out the contents of RAM to the swap partition before turning off the machine. In this case the size of the swap partition should be at least as large as the system's installed RAM.

Swapping is never good. For mechanical hard drives you can generally tell if a system is swapping by just listening to disk activity and observing how the system reacts to commands. For an SSD drive you will not be able to hear swapping but you can tell how much swap space is being used by the top or free programs. Use of an SSD drive for a swap partition should be avoided if possible. The first reaction to swapping should be to check for an unreasonable command such as trying to edit a five gigabyte file. If swapping becomes a normal occurrence, the best solution is to purchase more RAM for your system.

2.4.1.3. Convenience Partitions

There are several other partitions that are not required, but should be considered when designing a disk layout. The following list is not comprehensive, but is meant as a guide.

/boot – Highly recommended. Use this partition to store kernels and other booting information. To minimize potential boot problems with larger disks, make this the first physical partition on your first disk drive. A partition size of 200 megabytes is quite adequate.
/home – Highly recommended. Share your home directory and user customization across multiple distributions or LFS builds. The size is generally fairly large and depends on available disk space.
/usr – In LFS, /bin, /lib, and /sbin are symlinks to their counterpart in /usr. So /usr contains all binaries needed for the system to run. For LFS a separate partition for /usr is normally not needed. If you need it anyway, you should make a partition large enough to fit all programs and libraries in the system. The root partition can be very small (maybe just one gigabyte) in this configuration, so it's suitable for a thin client or diskless workstation (where /usr is mounted from a remote server). However you should take care that an initramfs (not covered by LFS) will be needed to boot a system with separate /usr partition.
/opt – This directory is most useful for BLFS where multiple installations of large packages like Gnome or KDE can be installed without embedding the files in the /usr hierarchy. If used, 5 to 10 gigabytes is generally adequate.
/tmp – A separate /tmp directory is rare, but useful if configuring a thin client. This partition, if used, will usually not need to exceed a couple of gigabytes.
/usr/src – This partition is very useful for providing a location to store BLFS source files and share them across LFS builds. It can also be used as a location for building BLFS packages. A reasonably large partition of 30-50 gigabytes allows plenty of room.

Any separate partition that you want automatically mounted upon boot needs to be specified in the /etc/fstab. Details about how to specify partitions will be discussed in Section 10.2, “Creating the /etc/fstab File”.