What is linux boot partition

Ubuntu Documentation

The goal of this page is to offer advice and strategy on partitioning a Linux system.

Overview

The easiest partitioning scheme, on a non-GPT disk, is simply a root partition and a swap partition.

Name

Size

size of RAM

the rest of the disk

If the disk is GPT type (this can be checked via the «sudo parted -l» command), you must also add a BIOS-Boot or an EFI partition depending on the boot mode of your BIOS.

Name

Size

BIOS-boot or EFI

see below

size of RAM

the rest of the disk

On some computers, a separate /boot partition may also be required.

See paragraphs below.

Root partition (always required)

• Mount point: /
• Type: Linux type (generally EXT4)
• Description: the root partition contains by default all your system files, program settings and documents.
• Size: minimum is 8 GB. It is recommended to make it at least 15 GB. Warning: your system will be blocked if the root partition is full.

Swap (very recommended)

Description: see SwapFaq.

Size: size of your RAM.

Separate /boot (sometimes required)

Some computers can’t see boot files (/boot) if located far (>100GB) from the start of the disk. This is why it is sometimes necessary to create a separate /boot partition at the start of the disk. Remark: don’t use the same /boot for several Linux distributions, as it may mix up their kernels. See this tutorial if you want to create a separate /boot after installing Ubuntu.

Name

Size

at least size of RAM

minimum 8 GB, at least 15 GB recommended

BIOS-Boot or EFI partition (required on GPT disks)

If you want to install Ubuntu on a GPT disk (you can check it via the ‘sudo parted -l’ command), you will need either an EFI partition (if your BIOS is set up in EFI mode) or a BIOS-Boot partition (if your BIOS is set up in Legacy mode).

BIOS-Boot partition:

• Mount point: none
• Type: no filesystem
• Description: the BIOS-boot partition contains GRUB 2’s core. It is necessary if you install Ubuntu on a GPT disk, and if the firmware (BIOS) is set up in Legacy (not EFI) mode. It must be located at the start of a GPT disk, and have a «bios_grub» flag.
• Size: 1MB.

EFI partition:

• Mount point: /boot/efi (no need to set up this mount point as the installer will do it automatically)
• Type: FAT (generally FAT32)

Description: the EFI partition (also called ESP) contains some boot files. It is necessary if the firmware (BIOS) is set up to boot the HDD in EFI mode (which is default on more and more modern, > year 2011 computers). It must be located at the start of a GPT disk, and have a «boot» flag.
Size: 100

Optional partitions

Optionally, some other partitions can be created for specific usages. Be careful, these partitions reduce the flexibility of your disk space, they must be considered only if you are sure not to fill completely your root partition (which would block your system).

Partition for sharing data with Windows, MacOS. (optional)

• Mount point: /media/thenameyouwish
• Type: to share data with Windows, choose NTFS. To share data with MacOS, choose HFS+. To share data with another Linux system, choose EXT4.
• Description: other operating systems (Windows, MacOS..) cannot read nor write in the Ubuntu partitions, but Ubuntu can read and write in any partition. If you want to share files between Ubuntu and the other systems, it is recommended to create a data partition. It is not recommended to share files directly into the Windows system partition (eg files may be overwritten by hibernation).
• Size: as you wish

Separate /home (optional)

• Mount point: /home
• Type: Linux type (generally EXT4)

Description: see HomeFolder. When your hard disk is big enough, a separate /home allows to separate your settings (and also your data if you don’t use a data partition, see previous paragraph) from the rest of the system. A separate /home does not allow to share data with Windows nor MacOS (see previous paragraph).

Size: as you wish

More Complex Schemes

For more information on what various directories are used for, see The Linux Filesystem Hierarchy.

More complex schemes could involve creating a separate partition for any number of the default folders used by Ubuntu. System critical folders are important to protect, and since drives, and / or partitions do fail, it is often useful to have your file system broken down into as many small parts as possible. This can be over done however. Installing every core directory to its own partition could cause a noticeable degradation of performance.
Bearing that in mind, the following directories should NEVER be placed in their own separate partitions:

Name

Description

This directory stores the system wide executables that are accessible by most users.

This directory holds the executables used for core system functions, and used by the system administrator
to maintain the system. See Note Below

This is a system use directory containing process information. Almost never accessed by a user.

This directory contains system created links to your installed hardware, and like /proc is almost never accessed directly.

Note about /sbin

It can be argued, and reasonably so, that moving this directory to its own partition is a wise choice. If any of your partitions or drives should fail, then this directory / partition will be the one that most likely contains the tools you will need to repair it. So while moving this would decrease performance marginally, it could also be considered a wise move.

Sizes For Alternative Schemes

On a six month old installation of Ubuntu 10.04.3 LTS the disk usage could resemble something like this: (examples taken from my own system with many extra packages installed)

Actual

Name

Size

Recommended Partition Size

Everything not used elsewhere, or separate drive.

500 MB to 5 GB This directory is not used by mainline software packages, but mostly from packages coming from the universe repositories. If you do not use the universe repositories often, you probably will not need much space here.

DO NOT PARTITION

Unless you plan on installing web served data here, or are using a Server version of Ubuntu, this will not often need to be larger than 100 MB. If you are running a server, or plan to expand it yourself, plan ahead when sizing this.

This can get fairly large, but not larger than your swap space as a rule, so size this to match /swap

8 kB (do not partition)

This is just an empty directory that serves as a mount point for temporary file systems, e.g. a rarely used network filesystem.

8 kB (do not partition)

This contains subdirectories that are mount points for removable media like CDs and USB flash drives.

The above recommendations assume you are using large modern hard drives and can afford the space.

Space Requirements

Absolute Requirements

The required disk space for an out-of-the-box Ubuntu installation is said to be 15 GB. However, that does not take into account the space needed for a file-system or a swap partition.

It is more realistic to give yourself a little bit more than 15 GB of space. Give yourself 15-25 GB to have some space left for actually doing things. If your file-system is full to the brim, you will feel some performance loss.

A certain percentage of an ext3 file-system is dedicated to root, as a way of preventing a rogue process from filling the disk to the point that the system is unusable. This dedicated portion is 5% by default. Also, the anti-fragmentation strategies used by Linux file-systems require that the disk is not close to full. A rule of thumb is to keep them less than 90% full.

Installation on a small disk

(This section is out-of-date & may need research for sizes) During a normal install, the installer copies the packages from the CD to the hard drive (in addition to actually installing them). If you are short on disk space before you install, you can tell the installer not to use extra disk space. The packages take up about xxx Mb. You will be able to install a full Ubuntu system with less than xx GB of hard drive space.

At the installation prompt (just after you boot from CD) type:

DiskSpace (последним исправлял пользователь ckimes 2017-09-02 19:35:04)

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Partitioning

Disk partitioning or disk slicing is the creation of one or more regions on secondary storage, so that each region can be managed separately.

An entire disk may be allocated to a single partition, or multiple ones for cases such as dual-booting, maintaining a swap partition, or to logically separate data such as audio and video files. The partitioning scheme is stored in a partition table such as Master Boot Record (MBR) or GUID Partition Table (GPT).

Partition tables are created and modified using one of many partitioning tools. The tools available for Arch Linux are listed in the #Partitioning tools section.

Partitions usually contain a file system directly which is accomplished by creating a file system on (a.k.a. formatting) the partition. Alternatively, partitions can contain LVM, block device encryption or RAID, which ultimately provide device files on which a file system can be placed (or the devices can be stacked further).

Any block device (e.g. disk, partition, LUKS device, LVM logical volume or RAID array) that directly contains a mountable file system is called a volume.

Contents

Partition table

There are two main types of partition table available. These are described below in the #Master Boot Record (MBR) and #GUID Partition Table (GPT) sections along with a discussion on how to choose between the two. A third, less common alternative is using a partitionless disk, which is also discussed.

Use a partitioning tool to view the partition table of a block device.

Master Boot Record

The Master Boot Record (MBR) is the first 512 bytes of a storage device. It contains an operating system bootloader and the storage device’s partition table. It plays an important role in the boot process under BIOS systems. See Wikipedia:Master boot record#Disk partitioning for the MBR structure.

Master Boot Record (bootstrap code)

The first 440 bytes of MBR are the bootstrap code area. On BIOS systems it usually contains the first stage of the boot loader. The bootstrap code can be backed up, restored from backup or erased using dd.

Master Boot Record (partition table)

In the MBR partition table (also known as DOS or MS-DOS partition table) there are 3 types of partitions:

Primary partitions can be bootable and are limited to four partitions per disk or RAID volume. If the MBR partition table requires more than four partitions, then one of the primary partitions needs to be replaced by an extended partition containing logical partitions within it.

Extended partitions can be thought of as containers for logical partitions. A hard disk can contain no more than one extended partition. The extended partition is also counted as a primary partition so if the disk has an extended partition, only three additional primary partitions are possible (i.e. three primary partitions and one extended partition). The number of logical partitions residing in an extended partition is unlimited. A system that dual boots with Windows will require for Windows to reside in a primary partition.

The customary numbering scheme is to create primary partitions sda1 through sda3 followed by an extended partition sda4. The logical partitions on sda4 are numbered sda5, sda6, etc.

GUID Partition Table

GUID Partition Table (GPT) is a partitioning scheme that is part of the Unified Extensible Firmware Interface specification; it uses globally unique identifiers (GUIDs), or UUIDs in the Linux world, to define partitions and partition types. It is designed to succeed the Master Boot Record partitioning scheme method.

At the start of a GUID Partition Table disk there is a protective Master Boot Record (PMBR) to protect against GPT-unaware software. This protective MBR just like an ordinary MBR has a bootstrap code area which can be used for BIOS/GPT booting with boot loaders that support it.

Choosing between GPT and MBR

GUID Partition Table (GPT) is an alternative, contemporary, partitioning style; it is intended to replace the old Master Boot Record (MBR) system. GPT has several advantages over MBR which has quirks dating back to MS-DOS times. With the recent developments to the formatting tools, it is equally easy to get good dependability and performance for GPT or MBR.

Some points to consider when choosing:

• To dual-boot with Windows (both 32-bit and 64-bit) using Legacy BIOS, the MBR scheme is required.
• To dual-boot Windows 64-bit using UEFI mode instead of BIOS, the GPT scheme is required.
• If you are installing on older hardware, especially on old laptops, consider choosing MBR because its BIOS might not support GPT (but see below how to fix it).
• If you are partitioning a disk that is larger than 2 TiB, you need to use GPT.
• It is recommended to always use GPT for UEFI boot, as some UEFI implementations do not support booting to the MBR while in UEFI mode.
• If none of the above apply, choose freely between GPT and MBR. Since GPT is more modern, it is recommended in this case.

Some advantages of GPT over MBR are:

• Provides a unique disk GUID and unique partition GUID (PARTUUID) for each partition — A good filesystem-independent way of referencing partitions and disks.
• Provides a filesystem-independent partition name (PARTLABEL).
• Arbitrary number of partitions — depends on space allocated for the partition table — No need for extended and logical partitions. By default the GPT table contains space for defining 128 partitions. However if you want to define more partitions, you can allocate more space to the partition table (currently only gdisk is known to support this feature).
• Uses 64-bit LBA for storing Sector numbers — maximum addressable disk size is 2 ZiB. MBR is limited to addressing 2 TiB of space per drive.[1]
• Stores a backup header and partition table at the end of the disk that aids in recovery in case the primary ones are damaged.
• CRC32 checksums to detect errors and corruption of the header and partition table.

The section on #Partitioning tools contains a table indicating which tools are available for creating and modifying GPT and MBR tables.

Partitionless disk

This article or section needs expansion.

Partitionless disk a.k.a. superfloppy refers to a storage device without a partition table, having one file system occupying the whole storage device. The boot sector present on a partitionless device is called a volume boot record (VBR).

Btrfs partitioning

Btrfs can occupy an entire data storage device and replace the MBR or GPT partitioning schemes. See the Btrfs#Partitionless Btrfs disk instructions for details.

Partition scheme

This article or section needs expansion.

There are no strict rules for partitioning a hard drive, although one may follow the general guidance given below. A disk partitioning scheme is determined by various issues such as desired flexibility, speed, security, as well as the limitations imposed by available disk space. It is essentially personal preference. If you would like to dual boot Arch Linux and a Windows operating system please see Dual boot with Windows.

Single root partition

This scheme is the simplest and should be enough for most use cases. A swapfile can be created and easily resized as needed. It usually makes sense to start by considering a single / partition and then separate out others based on specific use cases like RAID, encryption, a shared media partition, etc.

Discrete partitions

This article or section needs expansion.

Separating out a path as a partition allows for the choice of a different filesystem and mount options. In some cases like a media partition, they can also be shared between operating systems.

Below are some example layouts that can be used when partitioning, and the following subsections detail a few of the directories which can be placed on their own separate partition and then mounted at mount points under / . See file-hierarchy(7) for a full description of the contents of these directories.

The root directory is the top of the hierarchy, the point where the primary filesystem is mounted and from which all other filesystems stem. All files and directories appear under the root directory / , even if they are stored on different physical devices. The contents of the root filesystem must be adequate to boot, restore, recover, and/or repair the system. Therefore, certain directories under / are not candidates for separate partitions.

The / partition or root partition is necessary and it is the most important. The other partitions can be replaced by it.

/ traditionally contains the /usr directory, which can grow significantly depending upon how much software is installed. 15–20 GiB should be sufficient for most users with modern hard disks. If you plan to store a swap file here, you might need a larger partition size.

The /boot directory contains the kernel and ramdisk images as well as the boot loader configuration file and boot loader stages. It also stores data that is used before the kernel begins executing user-space programs. /boot is not required for normal system operation, but only during boot and kernel upgrades (when regenerating the initial ramdisk).

A suggested size for /boot is 200 MiB unless you are using EFI system partition as /boot , in which case at least 260 MiB is recommended.

The /home directory contains user-specific configuration files, caches, application data and media files.

Separating out /home allows / to be re-partitioned separately, but note that you can still reinstall Arch with /home untouched even if it is not separate—the other top-level directories just need to be removed, and then pacstrap can be run.

You should not share home directories between users on different distributions, because they use incompatible software versions and patches. Instead, consider sharing a media partition or at least using different home directories on the same /home partition. The size of this partition varies.

The /var directory stores variable data such as spool directories and files, administrative and logging data, pacman’s cache, etc. It is used, for example, for caching and logging, and hence frequently read or written. Keeping it in a separate partition avoids running out of disk space due to flunky logs, etc.

It exists to make it possible to mount /usr as read-only. Everything that historically went into /usr that is written to during system operation (as opposed to installation and software maintenance) must reside under /var .

/var will contain, among other data, the pacman cache. Retaining these packages is helpful in case a package upgrade causes instability, requiring a downgrade to an older, archived package. The pacman cache will grow as the system is expanded and updated, but it can be safely cleared if space becomes an issue. 8–12 GiB on a desktop system should be sufficient for /var , depending on how much software will be installed.

One can consider mounting a «data» partition to cover various files to be shared by all users. Using the /home partition for this purpose is fine as well. The size of this partition varies.

A swap is a file or partition that provides disk space used as virtual memory. Swap files and swap partitions are equally performant, but swap files are much easier to resize as needed. A swap partition can potentially be shared between operating systems, but not if hibernation is used.

Historically, the general rule for swap partition size was to allocate twice the amount of physical RAM. As computers have gained ever larger memory capacities, this rule is outdated. For example, on average desktop machines with up to 512 MiB RAM, the 2× rule is usually adequate; if a sufficient amount of RAM (more than 1024 MiB) is available, it may be possible to have a smaller swap partition.

To use hibernation (a.k.a suspend to disk) it is advised to create the swap partition at the size of RAM. Although the kernel will try to compress the suspend-to-disk image to fit the swap space there is no guarantee it will succeed if the used swap space is significantly smaller than RAM. See Power management/Suspend and hibernate#Hibernation for more information.

Example layouts

This article or section needs expansion.

The following examples use /dev/sda as the example disk with /dev/sda1 as the first partition. The block device naming scheme will differ if you are partitioning a NVMe disk (e.g. /dev/nvme0n1 with partitions starting from /dev/nvme0n1p1 ) or an SD card or eMMC disk (e.g. /dev/mmcblk0 with partitions starting from /dev/mmcblk0p1 ). See Device file#Block device names for more information.

UEFI/GPT layout example

Mount point on the installed system	Partition	Partition type GUID	Partition attributes	Suggested size
/boot or /efi 1	/dev/sda1	C12A7328-F81F-11D2-BA4B-00A0C93EC93B : EFI system partition	At least 260 MiB
[SWAP]	/dev/sda2	0657FD6D-A4AB-43C4-84E5-0933C84B4F4F : Linux swap	More than 512 MiB
/	/dev/sda3	4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709 : Linux x86-64 root (/)	Remainder of the device

BIOS/MBR layout example

Mount point on the installed system	Partition	Partition type ID	Boot flag	Suggested size
[SWAP]	/dev/sda1	82 : Linux swap	No	More than 512 MiB
/	/dev/sda2	83 : Linux	Yes	Remainder of the device
N/A	Unallocated space 2	N/A	N/A	At least 16.5 KiB at the end of the disk

BIOS/GPT layout example

Mount point on the installed system	Partition	Partition type GUID	Partition attributes	Suggested size
None	/dev/sda1	21686148-6449-6E6F-744E-656564454649 : BIOS boot partition 3	1 MiB
[SWAP]	/dev/sda2	0657FD6D-A4AB-43C4-84E5-0933C84B4F4F : Linux swap	More than 512 MiB
/	/dev/sda3	4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709 : Linux x86-64 root (/)	Remainder of the device

1. The ESP can be mounted to /efi if the used boot loader is capable of accessing the file system (and everything above it) on which the kernel and initramfs images are located. See EFI system partition#Typical mount points and the warning in Arch boot process#Boot loader for details.
2. An unpartitioned space of at least 33 512-byte sectors (16.5 KiB) at the end of the disk to allow converting to GPT in the future. The space will be required for the backup GPT header. The recommendation to preserve an unpartitioned space applies to all MBR partitioned disks.
3. A BIOS boot partition is only required when using GRUB for BIOS booting from a GPT disk. The partition has nothing to do with /boot , and it must not be formatted with a file system or mounted.

Tools

Partitioning tools

The following programs are used to create and/or manipulate device partition tables and partitions. See the linked articles for the exact commands to be used.

This table will help you to choose utility for your needs:

MBR	GPT
Dialog	fdisk parted	fdisk gdisk parted
Pseudo-graphics	cfdisk	cfdisk cgdisk
Non-interactive	sfdisk parted	sfdisk sgdisk parted
Graphical	GParted gnome-disk-utility partitionmanager	GParted gnome-disk-utility partitionmanager

fdisk

fdisk and its related utilities are described in the fdisk article.

• fdisk ( util-linux )
  • fdisk(8) – Dialog-driven program for creation and manipulation of partition tables.
  • cfdisk(8) – Curses-based variant of fdisk.
  • sfdisk(8) – Scriptable variant of fdisk.

GPT fdisk

gdisk and its related utilities are described in the gdisk article.

GNU Parted

These group of tools are described in the GNU Parted article.

Backup

• fdisk can create a backup of the partitions table. See fdisk#Backup and restore partition table.
• GPT fdisk can create a binary backup consisting of the protective MBR, the main GPT header, the backup GPT header, and one copy of the partition table. See GPT fdisk#Backup and restore partition table.

Recovery

• gpart — A utility that guesses the contents of a destroyed MBR partition table. Its usage is explained in the gpart(8) man page.

https://github.com/baruch/gpart || gpart

• GPT fdisk — A partitioning tool that can restore the primary GPT header (located at the start of the disk) from the secondary GPT header (located at the end of the disk) or vice versa.

https://www.rodsbooks.com/gdisk/ || gptfdisk

• TestDisk — A utility that supports recovering lost partitions on both MBR and GPT.

https://www.cgsecurity.org/index.html?testdisk.html || testdisk

Partition alignment

fdisk, gdisk and parted handle alignment automatically. See GNU Parted#Check alignment if you want to verify your alignment after partitioning.

For certain drives Advanced Format might be able to provide a better-performing alignment.

GPT kernel support

The CONFIG_EFI_PARTITION option in the kernel config enables GPT support in the kernel (despite the name, EFI PARTITION). This option must be built in the kernel and not compiled as a loadable module. This option is required even if GPT disks are used only for data storage and not for booting. This option is enabled by default in all Arch’s officially supported kernels. In case of a custom kernel, enable this option by doing CONFIG_EFI_PARTITION=y .

Troubleshooting

This article or section needs expansion.

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