Translations:Handbook:X86/Installation/Disks/1/en
Introduction to block devices
Block devices
Let's take a good look at disk-oriented aspects of Gentoo Linux and Linux in general, including block devices, partitions, and Linux filesystems. Once the ins and outs of disks are understood, partitions and filesystems can be established for installation.
To begin, let's look at block devices. SCSI and Serial ATA drives are both labeled under device handles such as: /dev/sda, /dev/sdb, /dev/sdc, etc. On more modern machines, PCI Express based NVMe solid state disks have device handles such as /dev/nvme0n1, /dev/nvme0n2, etc.
The following table will help readers determine where to find a certain type of block device on the system:
| Type of device | Default device handle | Editorial notes and considerations |
|---|---|---|
| IDE, SATA, SAS, SCSI, or USB flash | /dev/sda | Found on hardware from roughly 2007 until the present, this device handle is perhaps the most commonly used in Linux. These types of devices can be connected via the SATA bus, SCSI, USB bus as block storage. As example, the first partition on the first SATA device is called /dev/sda1. |
| NVM Express (NVMe) | /dev/nvme0n1 | The latest in solid state technology, NVMe drives are connected to the PCI Express bus and have the fastest transfer block speeds on the market. Systems from around 2014 and newer may have support for NVMe hardware. The first partition on the first NVMe device is called /dev/nvme0n1p1. |
| MMC, eMMC, and SD | /dev/mmcblk0 | embedded MMC devices, SD cards, and other types of memory cards can be useful for data storage. That said, many systems may not permit booting from these types of devices. It is suggested to not use these devices for active Linux installations; rather consider using them to transfer files, which is their typical design intention. Alternatively this storage type could be useful for short-term file backups or snapshots. |
The block devices above represent an abstract interface to the disk. User programs can use these block devices to interact with the disk without worrying about whether the drives are SATA, SCSI, or something else. The program can simply address the storage on the disk as a bunch of contiguous, randomly-accessible 4096-byte (4K) blocks.
Introduction to block devices
Block devices
Placeholder for introduction to block devices specific to the relative architecture.
Designing a partition scheme
Placeholder for designing a partition scheme specific to the relative architecture.
Creating file systems
When using SSD or NVMe drive, it is wise to check for firmware upgrades. Some Intel SSDs in particular (600p and 6000p) require a firmware upgrade for possible data corruption induced by XFS I/O usage patterns. The problem is at the firmware level and not any fault of the XFS filesystem. The smartctl utility can help check the device model and firmware version.
Introduction
Now that the partitions have been created, it is time to place a filesystem on them. In the next section the various file systems that Linux supports are described. Readers that already know which filesystem to use can continue with Applying a filesystem to a partition. The others should read on to learn about the available filesystems...
Filesystems
Linux supports several dozen filesystems, although many of them are only wise to deploy for specific purposes. Only certain filesystems may be found stable on the architecture - it is advised to read up on the filesystems and their support state before selecting a more experimental one for important partitions. XFS is the recommended all-purpose, all-platform filesystem. The below is a non-exhaustive list:
- XFS
- Filesystem with metadata journaling which comes with a robust feature-set and is optimized for scalability. It has been continuously upgraded to include modern features. The only downside is that XFS partitions cannot yet be shrunk, although this is being worked on. XFS notably supports reflinks and Copy on Write (CoW) which is particularly helpful on Gentoo systems because of the amount of compiles users complete. XFS is the recommended modern all-purpose all-platform filesystem. Requires a partition to be at least 300MB.
- ext4
- Ext4 is a reliable, all-purpose all-platform filesystem, although it lacks modern features like reflinks.
- VFAT
- Also known as FAT32, is supported by Linux but does not support standard UNIX permission settings. It is mostly used for interoperability/interchange with other operating systems (Microsoft Windows or Apple's macOS) but is also a necessity for some system bootloader firmware (like UEFI). Users of UEFI systems will need an EFI System Partition formatted with VFAT in order to boot.
- btrfs
- Newer generation filesystem. Provides advanced features like snapshotting, self-healing through checksums, transparent compression, subvolumes, and integrated RAID. Kernels prior to 5.4.y are not guaranteed to be safe to use with btrfs in production because fixes for serious issues are only present in the more recent releases of the LTS kernel branches. RAID 5/6 and quota groups unsafe on all versions of btrfs.
- F2FS
- The Flash-Friendly File System was originally created by Samsung for the use with NAND flash memory. It is a decent choice when installing Gentoo to microSD cards, USB drives, or other flash-based storage devices.
- NTFS
- This "New Technology" filesystem is the flagship filesystem of Microsoft Windows since Windows NT 3.1. Similarly to VFAT, it does not store UNIX permission settings or extended attributes necessary for BSD or Linux to function properly, therefore it should not be used as a root filesystem for most cases. It should only be used for interoperability or data interchange with Microsoft Windows systems (note the emphasis on only).
- ZFS Important: ZFS pools can only be created on the admincd and LiveGUI ISOs, for further information, refer to ZFS/rootfs
- Next generation file system created by Matthew Ahrens and Jeff Bonwick. It was designed around a few key ideas: Administration of storage should be simple, redundancy should be handled by the filesystem, file systems should never be taken offline for repair, automated simulations of worst case scenarios before shipping code is important, and data integrity is paramount.
More extensive information on filesystems can be found in the community maintained Filesystem article.
Applying a filesystem to a partition
Please make sure to emerge the relevant user space utilities package for the chosen filesystem before rebooting. There will be a reminder to do so near the end of the installation process.
To create a filesystem on a partition or volume, there are user space utilities available for each possible filesystem. Click the filesystem's name in the table below for additional information on each filesystem:
| Filesystem | Creation command | Within the live environment? | Package |
|---|---|---|---|
| XFS | mkfs.xfs | Yes | sys-fs/xfsprogs |
| ext4 | mkfs.ext4 | Yes | sys-fs/e2fsprogs |
| VFAT (FAT32, ...) | mkfs.vfat | Yes | sys-fs/dosfstools |
| btrfs | mkfs.btrfs | Yes | sys-fs/btrfs-progs |
| F2FS | mkfs.f2fs | Yes | sys-fs/f2fs-tools |
| NTFS | mkfs.ntfs | Yes | sys-fs/ntfs3g |
| ZFS | zpool create ... | No | sys-fs/zfs |
The handbook recommends new partitions as part of the installation process, but it is important to note running any mkfs command will erase any data contained within the partition. When necessary, ensure any data that exists within is appropriately backed up before creating a new filesystem.
For instance, to have the root partition () as as used in the example partition structure, the following commands would be used:
root #mkfs.
Legacy BIOS boot partition filesystem
Systems booting via legacy BIOS with a MBR/DOS disklabel can use any filesystem format supported by the bootloader.
For example, to format with XFS:
root #mkfs.xfs Small ext4 partitions
When using the ext4 filesystem on a small partition (less than 8 GiB), the filesystem should be created with the proper options to reserve enough inodes. This can specified using the -T small option:
root #mkfs.ext4 -T small /dev/<device>Doing so will quadruple the number of inodes for a given filesystem, since its "bytes-per-inode" reduces from one every 16kB to one every 4kB.
Activating the swap partition
mkswap is the command that is used to initialize swap partitions:
root #mkswap To activate the swap partition, use swapon:
root #swapon This 'activation' step is only necessary because the swap partition is newly created within the live environment. Once the system has been rebooted, as long as the swap partition is properly defined within fstab or other mount mechanism, swap space will activate automatically.
Mounting the root partition
Installations which were previously started, but did not finish the installation process can resume the installation from this point in the handbook. Use this link as the permalink: Resumed installations start here.
Certain live environments may be missing the suggested mount point for Gentoo's root partition (), or mount points for additional partitions created in the partitioning section:
root #mkdir --parents Continue creating additional mount points necessary for any additional (custom) partition(s) created during previous steps by using the mkdir command.
With mount points created, it is time to make the partitions accessible via mount command.
Mount the root partition:
root #mount
Continue mounting additional (custom) partitions as necessary using the mount command.
If /tmp/ needs to reside on a separate partition, be sure to change its permissions after mounting:
root #chmod 1777 /tmpLater in the instructions, the proc filesystem (a virtual interface with the kernel) as well as other kernel pseudo-filesystems will be mounted. But first the Gentoo stage file must be extracted.