Tag: lvm

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Choose between Btrfs and LVM-ext4

Fedora 33 introduced a new default filesystem in desktop variants, Btrfs. After years of Fedora using ext4 on top of Logical Volume Manager (LVM) volumes, this is a big shift. Changing the default file system requires compelling reasons. While Btrfs is an exciting next-generation file system, ext4 on LVM is well established and stable. This guide aims to explore the high-level features of each and make it easier to choose between Btrfs and LVM-ext4.

In summary

The simplest advice is to stick with the defaults. A fresh Fedora 33 install defaults to Btrfs and upgrading a previous Fedora release continues to use whatever was initially installed, typically LVM-ext4. For an existing Fedora user, the cleanest way to get Btrfs is with a fresh install. However, a fresh install is much more disruptive than a simple upgrade. Unless there is a specific need, this disruption could be unnecessary. The Fedora development team carefully considered both defaults, so be confident with either choice.

What about all the other file systems?

There are a large number of file systems for Linux systems. The number explodes after adding in combinations of volume managers, encryption methods, and storage mechanisms . So why focus on Btrfs and LVM-ext4? For the Fedora audience these two setups are likely to be the most common. Ext4 on top of LVM became the default disk layout in Fedora 11, and ext3 on top of LVM came before that.

Now that Btrfs is the default for Fedora 33, the vast majority of existing users will be looking at whether they should stay where they are or make the jump forward. Faced with a fresh Fedora 33 install, experienced Linux users may wonder whether to use this new file system or fall back to what they are familiar with. So out of the wide field of possible storage options, many Fedora users will wonder how to choose between Btrfs and LVM-ext4.

Commonalities

Despite core differences between the two setups, Btrfs and LVM-ext4 actually have a lot in common. Both are mature and well-tested storage technologies. LVM has been in continuous use since the early days of Fedora Core and ext4 became the default in 2009 with Fedora 11. Btrfs merged into the mainline Linux kernel in 2009 and Facebook uses it widely. SUSE Linux Enterprise 12 made it the default in 2014. So there is plenty of production run time there as well.

Both systems do a great job preventing file system corruption due to unexpected power outages, even though the way they accomplish it is different. Supported configurations include single drive setups as well as spanning multiple devices, and both are capable of creating nearly instant snapshots. A variety of tools exist to help manage either system, both with the command line and graphical interfaces. Either solution works equally well on home desktops and on high-end servers.

Advantages of LVM-ext4

Show the relationship of LVM-ext4 filesystem to hard-drive partitions and mounted directories.
Structure of ext4 on LVM

The ext4 file system focuses on high-performance and scalability, without a lot of extra frills. It is effective at preventing fragmentation over extended periods of time and provides nice tools for when it does happen. Ext4 is rock solid because it built on the previous ext3 file system, bringing with it all the years of in-system testing and bug fixes.

Most of the advanced capabilities in the LVM-ext4 setup come from LVM itself. LVM sits “below” the file system, which means it supports any file system. Logical volumes (LV) are generic block devices so virtual machines can use them directly. This flexibility allows each logical volume to use the right file system, with the right options, for a variety of situations. This layered approach also honors the Unix philosophy of small tools working together.

The volume group (VG) abstraction from the hardware allows LVM to create flexible logical volumes. Each LV pulls from the same storage pool but has its own configuration. Resizing volumes is a lot easier than resizing physical partitions as there are no limitation of ordered placement of the data. LVM physical volumes (PV) can be any number of partitions and can even move between devices while the system is running.

LVM supports read-only and read-write snapshots, which make it easy to create consistent backups from active systems. Each snapshot has a defined size, and a change to the source or snapshot volume use space from there. Alternately, logical volumes can also be part of a thinly provisioned pool. This allows snapshots to automatically use data from a pool instead of consuming fixed sized chunks defined at volume creation.

Multiple devices with LVM

LVM really shines when there are multiple devices. It has native support for most RAID levels and each logical volume can have a different RAID level. LVM will automatically choose appropriate physical devices for the RAID configuration or the user can specify it directly. Basic RAID support includes data striping for performance (RAID0) and mirroring for redundancy (RAID1). Logical volumes can also use advanced setups like RAID5, RAID6, and RAID10. LVM RAID support is mature because under the hood LVM uses the same device-mapper (dm) and multiple-device (md) kernel support used by mdadm.

Logical volumes can also be cached volumes for systems with both fast and slow drives. A classic example is a combination of SSD and spinning-disk drives. Cached volumes use faster drives for more frequently accessed data (or as a write cache), and the slower drive for bulk data.

The large number of stable features in LVM and the reliable performance of ext4 are a testament to how long they have been in use. Of course, with more features comes complexity. It can be challenging to find the right options for the right feature when configuring LVM. For single drive desktop systems, features of LVM like RAID and cache volumes don’t apply. However, logical volumes are more flexible than physical partitions and snapshots are useful. For normal desktop use, the complexity of LVM can also be a barrier to recovering from issues a typical user might encounter.

Advantages of Btrfs

Show the relationship of Btrfs filesystem to hard-drive partitions and mounted directories.
Btrfs Structure

Lessons learned from previous generations guided the features built into Btrfs. Unlike ext4, it can directly span multiple devices, so it brings along features typically found only in volume managers. It also has features that are unique in the Linux file system space (ZFS has a similar feature set, but don’t expect it in the Linux kernel).

Key Btrfs features

Perhaps the most important feature is the checksumming of all data. Checksumming, along with copy-on-write, provides the key method of ensuring file system integrity after unexpected power loss. More uniquely, checksumming can detect errors in the data itself. Silent data corruption, sometimes referred to as bitrot, is more common that most people realize. Without active validation, corruption can end up propagating to all available backups. This leaves the user with no valid copies. By transparently checksumming all data, Btrfs is able to immediately detect any such corruption. Enabling the right dup or raid option allows the file system to transparently fix the corruption as well.

Copy-on-write (COW) is also a fundamental feature of Btrfs, as it is critical in providing file system integrity and instant subvolume snapshots. Snapshots automatically share underlying data when created from common subvolumes. Additionally, after-the-fact deduplication uses the same technology to eliminate identical data blocks. Individual files can use COW features by calling cp with the reflink option. Reflink copies are especially useful for copying large files, such as virtual machine images, that tend to have mostly identical data over time.

Btrfs supports spanning multiple devices with no volume manager required. Multiple device support unlocks data mirroring for redundancy and striping for performance. There is also experimental support for more advanced RAID levels, such as RAID5 and RAID6. Unlike standard RAID setups, the Btrfs raid1 option actually allows an odd number of devices. For example, it can use 3 devices, even if they are are different sizes.

All RAID and dup options are specified at the file system level. As a consequence, individual subvolumes cannot use different options. Note that using the RAID1 option with multiple devices means that all data in the volume is available even if one device fails and the checksum feature maintains the integrity of the data itself. That is beyond what current typical RAID setups can provide.

Additional features

Btrfs also enables quick and easy remote backups. Subvolume snapshots can be sent to a remote system for storage. By leveraging the inherent COW meta-data in the file system, these transfers are efficient by only sending incremental changes from previously sent snapshots. User applications such as snapper make it easy to manage these snapshots.

Additionally, a Btrfs volume can have transparent compression and chattr +c will mark individual files or directories for compression. Not only does compression reduce the space consumed by data, but it helps extend the life of SSDs by reducing the volume of write operations. Compression certainly introduces additional CPU overhead, but a lot of options are available to dial in the right trade-offs.

The integration of file system and volume manager functions by Btrfs means that overall maintenance is simpler than LVM-ext4. Certainly this integration comes with less flexibility, but for most desktop, and even server, setups it is more than sufficient.

Btrfs on LVM

Btrfs can convert an ext3/ext4 file system in place. In-place conversion means no data to copy out and then back in. The data blocks themselves are not even modified. As a result, one option for an existing LVM-ext4 systems is to leave LVM in place and simply convert ext4 over to Btrfs. While doable and supported, there are reasons why this isn’t the best option.

Some of the appeal of Btrfs is the easier management that comes with a file system integrated with a volume manager. By running on top of LVM, there is still some other volume manager in play for any system maintenance. Also, LVM setups typically have multiple fixed sized logical volumes with independent file systems. While Btrfs supports multiple volumes in a given computer, many of the nice features expect a single volume with multiple subvolumes. The user is still stuck manually managing fixed sized LVM volumes if each one has an independent Btrfs volume. Though, the ability to shrink mounted Btrfs filesystems does make working with fixed sized volumes less painful. With online shrink there is no need to boot a live image.

The physical locations of logical volumes must be carefully considered when using the multiple device support of Btrfs. To Btrfs, each LV is a separate physical device and if that is not actually the case, then certain data availability features might make the wrong decision. For example, using raid1 for data typically provides protection if a single drive fails. If the actual logical volumes are on the same physical device, then there is no redundancy.

If there is a strong need for some particular LVM feature, such as raw block devices or cached logical volumes, then running Btrfs on top of LVM makes sense. In this configuration, Btrfs still provides most of its advantages such as checksumming and easy sending of incremental snapshots. While LVM has some operational overhead when used, it is no more so with Btrfs than with any other file system.

Wrap up

When trying to choose between Btrfs and LVM-ext4 there is no single right answer. Each user has unique requirements, and the same user may have different systems with different needs. Take a look at the feature set of each configuration, and decide if there is something compelling about one over the other. If not, there is nothing wrong with sticking with the defaults. There are excellent reasons to choose either setup.

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Add storage to your Fedora system with LVM

Sometimes there is a need to add another disk to your system. This is where Logical Volume Management (LVM) comes in handy. The cool thing about LVM is that it’s fairly flexible. There are several ways to add a disk. This article describes one way to do it.

Heads up!

This article does not cover the process of physically installing a new disk drive into your system. Consult your system and disk documentation on how to do that properly.

Important: Always make sure you have backups of important data. The steps described in this article will destroy data if it already exists on the new disk.

Good to know

This article doesn’t cover every LVM feature deeply; the focus is on adding a disk. But basically, LVM has volume groups, made up of one or more partitions and/or disks. You add the partitions or disks as physical volumes. A volume group can be broken down into many logical volumes. Logical volumes can be used as any other storage for filesystems, ramdisks, etc. More information can be found here.

Think of the physical volumes as forming a pool of storage (a volume group) from which you then carve out logical volumes for your system to use directly.

Preparation

Make sure you can see the disk you want to add. Use lsblk prior to adding the disk to see what storage is already available or in use.

$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
zram0 251:0 0 989M 0 disk [SWAP]
vda 252:0 0 20G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 19G 0 part
└─fedora_fedora-root 253:0 0 19G 0 lvm /

This article uses a virtual machine with virtual storage. Therefore the device names start with vda for the first disk, vdb for the second, and so on. The name of your device may be different. Many systems will see physical disks as sda for the first disk, sdb for the second, and so on.

Once the new disk has been connected and your system is back up and running, use lsblk again to see the new block device.

$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
zram0 251:0 0 989M 0 disk [SWAP]
vda 252:0 0 20G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 19G 0 part
└─fedora_fedora-root 253:0 0 19G 0 lvm /
vdb 252:16 0 10G 0 disk

There is now a new device named vdb. The location for the device is /dev/vdb.

$ ls -l /dev/vdb
brw-rw----. 1 root disk 252, 16 Nov 24 12:56 /dev/vdb

We can see the disk, but we cannot use it with LVM yet. If you run blkid you should not see it listed. For this and following commands, you’ll need to ensure your system is configured so you can use sudo:

$ sudo blkid
/dev/vda1: UUID="4847cb4d-6666-47e3-9e3b-12d83b2d2448" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="830679b8-01"
/dev/vda2: UUID="k5eWpP-6MXw-foh5-Vbgg-JMZ1-VEf9-ARaGNd" TYPE="LVM2_member" PARTUUID="830679b8-02"
/dev/mapper/fedora_fedora-root: UUID="f8ab802f-8c5f-4766-af33-90e78573f3cc" BLOCK_SIZE="4096" TYPE="ext4"
/dev/zram0: UUID="fc6d7a48-2bd5-4066-9bcf-f062b61f6a60" TYPE="swap"

Add the disk to LVM

Initialize the disk using pvcreate. You need to pass the full path to the device. In this example it is /dev/vdb; on your system it may be /dev/sdb or another device name.

$ sudo pvcreate /dev/vdb
Physical volume "/dev/vdb" successfully created.

You should see the disk has been initialized as an LVM2_member when you run blkid:

$ sudo blkid
/dev/vda1: UUID="4847cb4d-6666-47e3-9e3b-12d83b2d2448" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="830679b8-01"
/dev/vda2: UUID="k5eWpP-6MXw-foh5-Vbgg-JMZ1-VEf9-ARaGNd" TYPE="LVM2_member" PARTUUID="830679b8-02"
/dev/mapper/fedora_fedora-root: UUID="f8ab802f-8c5f-4766-af33-90e78573f3cc" BLOCK_SIZE="4096" TYPE="ext4"
/dev/zram0: UUID="fc6d7a48-2bd5-4066-9bcf-f062b61f6a60" TYPE="swap"
/dev/vdb: UUID="4uUUuI-lMQY-WyS5-lo0W-lqjW-Qvqw-RqeroE" TYPE="LVM2_member"

You can list all physical volumes currently available using pvs:

$ sudo pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 fedora_fedora lvm2 a-- <19.00g 0
/dev/vdb lvm2 --- 10.00g 10.00g

/dev/vdb is listed as a PV (phsyical volume), but it isn’t assigned to a VG (Volume Group) yet.

Add the pysical volume to a volume group

You can find a list of available volume groups using vgs:

$ sudo vgs
VG #PV #LV #SN Attr VSize VFree
fedora_fedora 1 1 0 wz--n- 19.00g 0

In this example, there is only one volume group available. Next, add the physical volume to fedora_fedora:

$ sudo vgextend fedora_fedora /dev/vdb
Volume group "fedora_fedora" successfully extended

You should now see the physical volume is added to the volume group:

$ sudo pvs PV VG Fmt Attr PSize PFree
/dev/vda2 fedora_fedora lvm2 a– <19.00g 0
/dev/vdb fedora_fedora lvm2 a– <10.00g <10.00g

Look at the volume groups:

$ sudo vgs
VG #PV #LV #SN Attr VSize VFree
fedora_fedora 2 1 0 wz–n- 28.99g <10.00g

You can get a detailed list of the specific volume group and physical volumes as well:

$ sudo vgdisplay fedora_fedora
--- Volume group ---
VG Name fedora_fedora
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 2
Act PV 2
VG Size 28.99 GiB
PE Size 4.00 MiB
Total PE 7422
Alloc PE / Size 4863 / 19.00 GiB
Free PE / Size 2559 / 10.00 GiB
VG UUID C5dL2s-dirA-SQ15-TfQU-T3yt-l83E-oI6pkp

Look at the PV:

$ sudo pvdisplay /dev/vdb --- Physical volume --- PV Name /dev/vdb VG Name fedora_fedora PV Size 10.00 GiB / not usable 4.00 MiB Allocatable yes PE Size 4.00 MiB Total PE 2559 Free PE 2559 Allocated PE 0 PV UUID 4uUUuI-lMQY-WyS5-lo0W-lqjW-Qvqw-RqeroE

Now that we have added the disk, we can allocate space to logical volumes (LVs):

$ sudo lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root fedora_fedora -wi-ao---- 19.00g

Look at the logical volumes. Here’s a detailed look at the root LV:

$ sudo lvdisplay fedora_fedora/root
--- Logical volume ---
LV Path /dev/fedora_fedora/root
LV Name root
VG Name fedora_fedora
LV UUID yqc9cw-AvOw-G1Ni-bCT3-3HAa-qnw3-qUSHGM
LV Write Access read/write
LV Creation host, time fedora, 2020-11-24 11:44:36 -0500
LV Status available
LV Size 19.00 GiB
Current LE 4863
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0

Look at the size of the root filesystem and compare it to the logical volume size.

$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/fedora_fedora-root 19G 1.4G 17G 8% /

The logical volume and the filesystem both agree the size is 19G. Let’s add 5G to the root logical volume:

$ sudo lvresize -L +5G fedora_fedora/root
Size of logical volume fedora_fedora/root changed from 19.00 GiB (4863 extents) to 24.00 GiB (6143 extents).
Logical volume fedora_fedora/root successfully resized.

We now have 24G available to the logical volume. Look at the / filesystem.

$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/fedora_fedora-root 19G 1.4G 17G 8% /

We are still showing only 19G free. This is because the logical volume is not the same as the filesytem. To use the new space added to the logical volume, resize the filesystem.

$ sudo resize2fs /dev/fedora_fedora/root
resize2fs 1.45.6 (20-Mar-2020)
Filesystem at /dev/fedora_fedora/root is mounted on /; on-line resizing required
old_desc_blocks = 3, new_desc_blocks = 3
The filesystem on /dev/fedora_fedora/root is now 6290432 (4k) blocks long.

Look at the size of the filesystem.

$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/fedora_fedora-root 24G 1.4G 21G 7% /

As you can see, the root file system (/) has taken all of the space available on the logical volume and no reboot was needed.

You have now initialized a disk as a physical volume, and extended the volume group with the new physical volume. After that you increased the size of the logical volume, and resized the filesystem to use the new space from the logical volume.

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Reclaim hard-drive space with LVM

LVM is a tool for logical volume management which includes allocating disks, striping, mirroring and resizing logical volumes. It is commonly used on Fedora installations (prior to BTRFS as default it was LVM+Ext4). But have you ever started up your system to find a message like the image above, after you logged in? Uh oh, Gnome just said the home volume is almost out of space! Luckily, there is likely some space sitting around in another volume, unused and ready to re-alocate. Here’s how to reclaim hard-drive space with LVM.

The key to easily re-alocate space between volumes is the Logical Volume Manager (LVM). Fedora 32 and before use LVM to divide disk space by default. This technology is similar to standard hard-drive partitions, but LVM is a lot more flexible. LVM enables not only flexible volume size management, but also advanced capabilities such as read-write snapshots, striping or mirroring data across multiple drives, using a high-speed drive as a cache for a slower drive, and much more. All of these advanced options can get a bit overwhelming, but resizing a volume is straight-forward.

LVM basics

The volume group serves as the main container in the LVM system. By default Fedora only defines a single volume group, but there can be as many as needed. Actual hard-drive and hard-drive partitions are added to the volume group as physical volumes. Physical volumes add available free space to the volume group. A typical Fedora install has one formatted boot partition, and the rest of the drive is a partition configured as an LVM physical volume.

Out of this pool of available space, the volume group allocates one or more logical volumes. These volumes are similar to hard-drive partitions, but without the limitation of contiguous space on the disk. LVM logical volumes can even span multiple devices! Just like hard-drive partitions, logical volumes have a defined size and can contain any filesystem which can then be mounted to specific directories.

What’s needed

Confirm the system uses LVM with the gnome-disks application, and make sure there is free space available in some other volume. Without space to reclaim from another volume, this guide isn’t useful. A Fedora live CD/USB is also needed. Any file system that needs to shrink must be unmounted. Running from a live image allows all the volumes on the hard-disk to remain unmounted, even important directories like / and /home.

Use gnome-disks to verify free space.
Use gnome-disks to verify free space

A word of warning

No data should be lost by following this guide, but it does muck around with some very low-level and powerful commands. One mistake could destroy all data on the hard-drive. So backup all the data on the disk first!

Resizing LVM volumes

To begin, boot the Fedora live image and select Try Fedora at the dialog. Next, use the Run Command to launch the blivet-gui application (accessible by pressing Alt-F2, typing blivet-gui, then pressing enter). Select the volume group on the left under LVM. The logical volumes are on the right.

Explore logical volumes in blivet gui.
Explore logical volumes in blivet-gui

The logical volume labels consist of both the volume group name and the logical volume name. In the example, the volume group is “fedora_localhost-live” and there are “home”, “root”, and “swap” logical volumes allocated. To find the full volume, select each one, click on the gear icon, and choose resize. The slider in the resize dialog indicates the allowable sizes for the volume. The minimum value on the left is the space already in use within the file system, so this is the minimum possible volume size (without deleting data). The maximum value on the right is the greatest size the volume can have based on available free space in the volume group.

Use the resize dialog in blivet-gui to set the new volume sizes.
Resize dialog in blivet-gui

A grayed out resize option means the volume is full and there is no free space in the volume group. It’s time to change that! Look through all of the volumes to find one with plenty of extra space, like in the screenshot above. Move the slider to the left to set the new size. Free up enough space to be useful for the full volume, but still leave plenty of space for future data growth. Otherwise, this volume will be the next to fill up.

Click resize and note that a new item appears in the volume listing: free space. Now select the full volume that started this whole endeavor, and move the slider all the way to the right. Press resize and marvel at the new improved volume layout. However, nothing has changed on the hard drive yet. Click on the check-mark to commit the changes to disk.

Review the changes in blivet-gui and then accept to reclaim hard-drive space.
Review changes in blivet-gui

Review the summary of the changes, and if everything looks right, click Ok to proceed. Wait for blivet-gui to finish. Now reboot back into the main Fedora install and enjoy all the new space in the previously full volume.

Planning for the future

It is challenging to know how much space any particular volume will need in the future. Instead of immediately allocating all available free space, consider leaving it free in the volume group. In fact, Fedora Server reserves space in the volume group by default. Extending a volume is possible while it is online and in use. No live image or reboot needed. When a volume is almost full, easily extend the volume using part of the available free space and keep working. Unfortunately the default disk manager, gnome-disks, does not support LVM volume resizing, so install blivet-gui for a graphical management tool. Alternately, there is a simple terminal command to extend a volume:

lvresize -r -L +1G /dev/fedora_localhost-live/root

Wrap-up

Reclaiming hard-drive space with LVM just scratches the surface of LVM capabilities. Most people, especially on the desktop, probably don’t need the more advanced features. However, LVM is there when the need arises, though it can get a bit complex to implement. BTRFS is the default filesystem, without LVM, starting with Fedora 33. BTRFS can be easier to manage while still flexible enough for most common usages. Check out the recent Fedora Magazine articles on BTRFS to learn more.

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Learning about Partitions and How to Create Them for Fedora

Operating system distributions try to craft a one size fits all partition layout for their file systems. Distributions cannot know the details about how your hardware is configured or how you use your system though. Do you have more than one storage drive? If so, you might be able to get a performance benefit by putting the write-heavy partitions (var and swap for example) on a separate drive from the others that tend to be more read-intensive since most drives cannot read and write at the same time. Or maybe you are running a database and have a small solid-state drive that would improve the database’s performance if its files are stored on the SSD.

The following sections attempt to describe in brief some of the historical reasons for separating some parts of the file system out into separate partitions so that you can make a more informed decision when you install your Linux operating system.

If you know more (or contradictory) historical details about the partitioning decisions that shaped the Linux operating systems used today, contribute what you know below in the comments section!

Common partitions and why or why not to create them

The boot partition

One of the reasons for putting the /boot directory on a separate partition was to ensure that the boot loader and kernel were located within the first 1024 cylinders of the disk. Most modern computers do not have the 1024 cylinder restriction. So for most people, this concern is no longer relevant. However, modern UEFI-based computers have a different restriction that makes it necessary to have a separate partition for the boot loader. UEFI-based computers require that the boot loader (which can be the Linux kernel directly) be on a FAT-formatted file system. The Linux operating system, however, requires a POSIX-compliant file system that can designate access permissions to individual files. Since FAT file systems do not support access permissions, the boot loader must be on a separate file system than the rest of the operating system on modern UEFI-based computers. A single partition cannot be formatted with more than one type of file system.

The var partition

One of the historical reasons for putting the /var directory on a separate partition was to prevent files that were frequently written to (/var/log/* for example) from filling up the entire drive. Since modern drives tend to be much larger and since other means like log rotation and disk quotas are available to manage storage utilization, putting /var on a separate partition may not be necessary. It is much easier to change a disk quota than it is to re-partition a drive.

Another reason for isolating /var was that file system corruption was much more common in the original version of the Linux Extended File System (EXT). The file systems that had more write activity were much more likely to be irreversibly corrupted by a power outage than those that did not. By partitioning the disk into separate file systems, one could limit the scope of the damage in the event of file system corruption. This concern is no longer as significant because modern file systems support journaling.

The home partition

Having /home on a separate partition makes it possible to re-format the other partitions without overwriting your home directories. However, because modern Linux distributions are much better at doing in-place operating system upgrades, re-formatting shouldn’t be needed as frequently as it might have been in the past.

It can still be useful to have /home on a separate partition if you have a dual-boot setup and want both operating systems to share the same home directories. Or if your operating system is installed on a file system that supports snapshots and rollbacks and you want to be able to rollback your operating system to an older snapshot without reverting the content in your user profiles. Even then, some file systems allow their descendant file systems to be rolled back independently, so it still may not be necessary to have a separate partition for /home. On ZFS, for example, one pool/partition can have multiple descendant file systems.

The swap partition

The swap partition reserves space for the contents of RAM to be written to permanent storage. There are pros and cons to having a swap partition. A pro of having swap memory is that it theoretically gives you time to gracefully shutdown unneeded applications before the OOM killer takes matters into its own hands. This might be important if the system is running mission-critical software that you don’t want abruptly terminated. A con might be that your system runs so slow when it starts swapping memory to disk that you’d rather the OOM killer take care of the problem for you.

Another use for swap memory is hibernation mode. This might be where the rule that the swap partition should be twice the size of your computer’s RAM originated. Ideally, you should be able to put a system into hibernation even if nearly all of its RAM is in use. Beware that Linux’s support for hibernation is not perfect. It is not uncommon that after a Linux system is resumed from hibernation some hardware devices are left in an inoperable state (for example, no video from the video card or no internet from the WiFi card).

In any case, having a swap partition is more a matter of taste. It is not required.

The root partition

The root partition (/) is the catch-all for all directories that have not been assigned to a separate partition. There is always at least one root partition. BIOS-based systems that are new enough to not have the 1024 cylinder limit can be configured with only a root partition and no others so that there is never a need to resize a partition or file system if space requirements change.

The EFI system partition

The EFI System Partition (ESP) serves the same purpose on UEFI-based computers as the boot partition did on the older BIOS-based computers. It contains the boot loader and kernel. Because the files on the ESP need to be accessible by the computer’s firmware, the ESP has a few restrictions that the older boot partition did not have. The restrictions are:

  1. The ESP must be formatted with a FAT file system (vfat in Anaconda)
  2. The ESP must have a special type-code (EF00 when using gdisk)

Because the older boot partition did not have file system or type-code restrictions, it is permissible to apply the above properties to the boot partition and use it as your ESP. Note, however, that the GRUB boot loader does not support combining the boot and ESP partitions. If you use GRUB, you will have to create a separate partition and mount it beneath the /boot directory.

The Boot Loader Specification (BLS) lists several reasons why it is ideal to use the legacy boot partition as your ESP. The reasons include:

  1. The UEFI firmware should be able to load the kernel directly. Having a separate, non-ESP compliant boot partition for the kernel prevents the UEFI firmware from being able to directly load the kernel.
  2. Nesting the ESP mount point three mount levels deep increases the likelihood that an intermediate mount could fail or otherwise be unavailable when needed. That is, requiring root (/), then boot (/boot), then efi (/efi) to be consecutively mounted is unnecessarily complex and prone to error.
  3. Requiring the boot loader to be able to read other partitions/disks which may be formatted with arbitrary file systems is non-trivial. Even when the boot loader does contain such code, the code that works at installation time can become outdated and fail to access the kernel/initrd after a file system update. This is currently true of GRUB’s ZFS file system driver, for example. You must be careful not to update your ZFS file system if you use the GRUB boot loader or else your system may not come back up the next time you reboot.

Besides the concerns listed above, it is a good idea to have your startup environment — up to and including your initramfs — on a single self-contained file system for recovery purposes. Suppose, for example, that you need to rollback your root file system because it has become corrupted or it has become infected with malware. If your kernel and initramfs are on the root file system, you may be unable to perform the recovery. By having the boot loader, kernel, and initramfs all on a single file system that is rarely accessed or updated, you can increase your chances of being able to recover the rest of your system.

In summary, there are many ways that you can layout your partitions and the type of hardware (BIOS or UEFI) and the brand of boot loader (GRUB, Syslinux or systemd-boot) are among the factors that will influence which layouts will work.

Other considerations

MBR vs. GPT

GUID Partition Table (GPT) is the newer partition format that supports larger disks. GPT was designed to work with the newer UEFI firmware. It is backward-compatible with the older Master Boot Record (MBR) partition format but not all boot loaders support the MBR boot method. GRUB and Syslinux support both MBR and UEFI, but systemd-boot only supports the newer UEFI boot method.

By using GPT now, you can increase the likelihood that your storage device, or an image of it, can be transferred over to a newer computer in the future should you wish to do so. If you have an older computer that natively supports only MBR-partitioned drives, you may need to add the inst.gpt parameter to Anaconda when starting the installer to get it to use the newer format. How to add the inst.gpt parameter is shown in the below video titled “Partitioning a BIOS Computer”.

If you use the GPT partition format on a BIOS-based computer, and you use the GRUB boot loader, you must additionally create a one megabyte biosboot partition at the start of your storage device. The biosboot partition is not needed by any other brand of boot loader. How to create the biosboot partition is demonstrated in the below video titled “Partitioning a BIOS Computer”.

LVM

One last thing to consider when manually partitioning your Linux system is whether to use standard partitions or logical volumes. Logical volumes are managed by the Logical Volume Manager (LVM). You can setup LVM volumes directly on your disk without first creating standard partitions to hold them. However, most computers still require that the boot partition be a standard partition and not an LVM volume. Consequently, having LVM volumes only increases the complexity of the system because the LVM volumes must be created within standard partitions.

The main features of LVM — online storage resizing and clustering — are not really applicable to the typical end user. Most laptops do not have hot-swappable drive bays for adding or reconfiguring storage while the system is running. And not many laptop or desktop users have clvmd configured so they can access a centralized storage device concurrently from multiple client computers.

LVM is great for servers and clusters. But it adds extra complexity for the typical end user. Go with standard partitions unless you are a server admin who needs the more advanced features.

Video demonstrations

Now that you know which partitions you need, you can watch the sort video demonstrations below to see how to manually partition a Fedora Linux computer from the Anaconda installer.

These videos demonstrate creating only the minimally required partitions. You can add more if you choose.

Because the GRUB boot loader requires a more complex partition layout on UEFI systems, the below video titled “Partitioning a UEFI Computer” additionally demonstrates how to install the systemd-boot boot loader. By using the systemd-boot boot loader, you can reduce the number of needed partitions to just two — boot and root. How to use a boot loader other than the default (GRUB) with Fedora’s Anaconda installer is officially documented here.

Partitioning a UEFI Computer
Partitioning a BIOS Computer