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Chapter 36. Managing storage devices

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36.1. Setting up Stratis file systems

Stratis runs as a service to manage pools of physical storage devices, simplifying local storage management with ease of use while helping you set up and manage complex storage configurations.

Important

Stratis is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

36.1.1. What is Stratis

Stratis is a local storage-management solution for Linux. It is focused on simplicity and ease of use, and gives you access to advanced storage features.

Stratis makes the following activities easier:

  • Initial configuration of storage
  • Making changes later
  • Using advanced storage features

Stratis is a hybrid user-and-kernel local storage management system that supports advanced storage features. The central concept of Stratis is a storage pool. This pool is created from one or more local disks or partitions, and volumes are created from the pool.

The pool enables many useful features, such as:

  • File system snapshots
  • Thin provisioning
  • Tiering

Additional resources

36.1.2. Components of a Stratis volume

Learn about the components that comprise a Stratis volume.

Externally, Stratis presents the following volume components in the command-line interface and the API:

blockdev
Block devices, such as a disk or a disk partition.
pool

Composed of one or more block devices.

A pool has a fixed total size, equal to the size of the block devices.

The pool contains most Stratis layers, such as the non-volatile data cache using the dm-cache target.

Stratis creates a /dev/stratis/my-pool/ directory for each pool. This directory contains links to devices that represent Stratis file systems in the pool.

filesystem

Each pool can contain one or more file systems, which store files.

File systems are thinly provisioned and do not have a fixed total size. The actual size of a file system grows with the data stored on it. If the size of the data approaches the virtual size of the file system, Stratis grows the thin volume and the file system automatically.

The file systems are formatted with XFS.

Important

Stratis tracks information about file systems created using Stratis that XFS is not aware of, and changes made using XFS do not automatically create updates in Stratis. Users must not reformat or reconfigure XFS file systems that are managed by Stratis.

Stratis creates links to file systems at the /dev/stratis/my-pool/my-fs path.

Note

Stratis uses many Device Mapper devices, which show up in dmsetup listings and the /proc/partitions file. Similarly, the lsblk command output reflects the internal workings and layers of Stratis.

36.1.3. Block devices usable with Stratis

Storage devices that can be used with Stratis.

Supported devices

Stratis pools have been tested to work on these types of block devices:

  • LUKS
  • LVM logical volumes
  • MD RAID
  • DM Multipath
  • iSCSI
  • HDDs and SSDs
  • NVMe devices
Unsupported devices

Because Stratis contains a thin-provisioning layer, Red Hat does not recommend placing a Stratis pool on block devices that are already thinly-provisioned.

36.1.4. Installing Stratis

Install the required packages for Stratis.

Procedure

  1. Install packages that provide the Stratis service and command-line utilities: 

    # yum install stratisd stratis-cli

  2. Verify that the stratisd service is enabled: 

    # systemctl enable --now stratisd

36.1.5. Creating an unencrypted Stratis pool

You can create an unencrypted Stratis pool from one or more block devices.

Prerequisites

  • Stratis is installed. For more information, see Installing Stratis.
  • The stratisd service is running.
  • The block devices on which you are creating a Stratis pool are not in use and are not mounted.
  • Each block device on which you are creating a Stratis pool is at least 1 GB.
  • On the IBM Z architecture, the /dev/dasd* block devices must be partitioned. Use the partition in the Stratis pool.

For information on partitioning DASD devices, see Configuring a Linux instance on IBM Z.

Note

You cannot encrypt an unencrypted Stratis pool.

Procedure

  1. Erase any file system, partition table, or RAID signatures that exist on each block device that you want to use in the Stratis pool: 

    # wipefs --all block-device

    where block-device is the path to the block device; for example, /dev/sdb.

  2. Create the new unencrypted Stratis pool on the selected block device: 

    # stratis pool create my-pool block-device

    where block-device is the path to an empty or wiped block device.

    Note

    Specify multiple block devices on a single line: 

    # stratis pool create my-pool block-device-1 block-device-2

  3. Verify that the new Stratis pool was created: 

    # stratis pool list

36.1.6. Creating an encrypted Stratis pool

To secure your data, your can create an encrypted Stratis pool from one or more block devices.

When you create an encrypted Stratis pool, the kernel keyring is used as the primary encryption mechanism. After subsequent system reboots this kernel keyring is used to unlock the encrypted Stratis pool.

When creating an encrypted Stratis pool from one or more block devices, note the following:

  • Each block device is encrypted using the cryptsetup library and implements the LUKS2 format.
  • Each Stratis pool can either have a unique key or share the same key with other pools. These keys are stored in the kernel keyring.
  • The block devices that comprise a Stratis pool must be either all encrypted or all unencrypted. It is not possible to have both encrypted and unencrypted block devices in the same Stratis pool.
  • Block devices added to the data tier of an encrypted Stratis pool are automatically encrypted.

Prerequisites

  • Stratis v2.1.0 or later is installed. For more information, see Installing Stratis.
  • The stratisd service is running.
  • The block devices on which you are creating a Stratis pool are not in use and are not mounted.
  • The block devices on which you are creating a Stratis pool are at least 1GB in size each.
  • On the IBM Z architecture, the /dev/dasd* block devices must be partitioned. Use the partition in the Stratis pool.

For information on partitioning DASD devices, see Configuring a Linux instance on IBM Z.

Procedure

  1. Erase any file system, partition table, or RAID signatures that exist on each block device that you want to use in the Stratis pool: 

    # wipefs --all block-device

    where block-device is the path to the block device; for example, /dev/sdb.

  2. If you have not created a key set already, run the following command and follow the prompts to create a key set to use for the encryption. 

    # stratis key set --capture-key key-description

    where key-description is a reference to the key that gets created in the kernel keyring.

  3. Create the encrypted Stratis pool and specify the key description to use for the encryption. You can also specify the key path using the --keyfile-path option instead instead of using the key-description option. 

    # stratis pool create --key-desc key-description my-pool block-device

    where

    key-description
    References the key that exists in the kernel keyring, which you created in the previous step.
    my-pool
    Specifies the name of the new Stratis pool.
    block-device

    Specifies the path to an empty or wiped block device.

    Note

    Specify multiple block devices on a single line: 

    # stratis pool create --key-desc key-description my-pool block-device-1 block-device-2

  4. Verify that the new Stratis pool was created: 

    # stratis pool list

36.1.7. Setting up a thin provisioning layer in Stratis filesystem

A storage stack can reach a state of overprovision. If the file system size becomes bigger than the pool backing it, the pool becomes full. To prevent this, disable overprovisioning, which ensures that the size of all filesystems on the pool does not exceed the available physical storage provided by the pool. If you use Stratis for critical applications or the root filesystem, this mode prevents certain failure cases.

If you enable overprovisioning, an API signal notifies you when your storage has been fully allocated. The notification serves as a warning to the user to inform them that when all the remaining pool space fills up, Stratis has no space left to extend to.

Prerequisites

Procedure

To set up the pool correctly, you have two possibilities:

  1. Create a pool from one or more block devices: 

    # stratis pool create --no-overprovision pool-name /dev/sdb
    • By using the --no-overprovision option, the pool cannot allocate more logical space than actual available physical space.

  2. Set overprovisioning mode in the existing pool: 

    # stratis pool overprovision pool-name <yes|no>
    • If set to "yes", you enable overprovisioning to the pool. This means that the sum of the logical sizes of the Stratis filesystems, supported by the pool, can exceed the amount of available data space.

Verification

  1. Run the following to view the full list of Stratis pools: 

    # stratis pool list

Name          Total Physical                    Properties     UUID                                   Alerts
pool-name     1.42 TiB / 23.96 MiB / 1.42 TiB   ~Ca,~Cr,~Op    cb7cb4d8-9322-4ac4-a6fd-eb7ae9e1e540
  2. Check if there is an indication of the pool overprovisioning mode flag in the stratis pool list output. The " ~ " is a math symbol for "NOT", so ~Op means no-overprovisioning.

  3. Optional: Run the following to check overprovisioning on a specific pool: 

    # stratis pool overprovision pool-name yes

# stratis pool list

Name          Total Physical                    Properties     UUID                                   Alerts
pool-name     1.42 TiB / 23.96 MiB / 1.42 TiB   ~Ca,~Cr,~Op    cb7cb4d8-9322-4ac4-a6fd-eb7ae9e1e540

Additional resources

36.1.8. Binding a Stratis pool to NBDE

Binding an encrypted Stratis pool to Network Bound Disk Encryption (NBDE) requires a Tang server. When a system containing the Stratis pool reboots, it connects with the Tang server to automatically unlock the encrypted pool without you having to provide the kernel keyring description.

Note

Binding a Stratis pool to a supplementary Clevis encryption mechanism does not remove the primary kernel keyring encryption.

Prerequisites

Procedure

  • Bind an encrypted Stratis pool to NBDE: 

    # stratis pool bind nbde --trust-url my-pool tang-server

    where

    my-pool
    Specifies the name of the encrypted Stratis pool.
    tang-server
    Specifies the IP address or URL of the Tang server.

Additional resources

36.1.9. Binding a Stratis pool to TPM

When you bind an encrypted Stratis pool to the Trusted Platform Module (TPM) 2.0, when the system containing the pool reboots, the pool is automatically unlocked without you having to provide the kernel keyring description.

Prerequisites

Procedure

  • Bind an encrypted Stratis pool to TPM: 

    # stratis pool bind tpm my-pool key-description

    where

    my-pool
    Specifies the name of the encrypted Stratis pool.
    key-description
    References the key that exists in the kernel keyring, which was generated when you created the encrypted Stratis pool.

36.1.10. Unlocking an encrypted Stratis pool with kernel keyring

After a system reboot, your encrypted Stratis pool or the block devices that comprise it might not be visible. You can unlock the pool using the kernel keyring that was used to encrypt the pool.

Prerequisites

Procedure

  1. Re-create the key set using the same key description that was used previously: 

    # stratis key set --capture-key key-description

    where key-description references the key that exists in the kernel keyring, which was generated when you created the encrypted Stratis pool.

  2. Unlock the Stratis pool and the block device that comprise it: 

    # stratis pool unlock keyring

  3. Verify that the Stratis pool is visible: 

    # stratis pool list

36.1.11. Unlocking an encrypted Stratis pool with Clevis

After a system reboot, your encrypted Stratis pool or the block devices that comprise it might not be visible. You can unlock an encrypted Stratis pool with the supplementary encryption mechanism that the pool is bound to.

Prerequisites

or Binding an encrypted Stratis pool to TPM.

Procedure

  1. Unlock the Stratis pool and the block devices that comprise it: 

    # stratis pool unlock clevis

  2. Verify that the Stratis pool is visible: 

    # stratis pool list

36.1.12. Unbinding a Stratis pool from supplementary encryption

When you unbind an encrypted Stratis pool from a supported supplementary encryption mechanism, the primary kernel keyring encryption remains in place.

Prerequisites

  • Stratis v2.3.0 or later is installed on your system. For more information, see Installing Stratis.
  • You have created an encrypted Stratis pool. For more information, see Creating an encrypted Stratis pool.
  • The encrypted Stratis pool is bound to a supported supplementary encryption mechanism.

Procedure

  • Unbind an encrypted Stratis pool from a supplementary encryption mechanism: 

    # stratis pool unbind clevis my-pool

    where

    my-pool specifies the name of the Stratis pool you want to unbind.

Additional resources

36.1.13. Starting and stopping Stratis pool

You can start and stop Stratis pools. This gives you the option to dissasemble or bring down all the objects that were used to construct the pool, such as filesystems, cache devices, thin pool, and encrypted devices. Note that if the pool actively uses any device or filesystem, it might issue a warning and not be able to stop.

Stopped pools record their stopped state in their metadata. These pools do not start on the following boot, until the pool receives a start command.

If not encrypted, previously started pools automatically start on boot. Encrypted pools always need a pool start command on boot, as pool unlock is replaced by pool start in this version of Stratis.

Prerequisites

or Creating an encrypted Stratis pool.

Procedure

  • Use the following command to start the Stratis pool. The --unlock-method option specifies the method of unlocking the pool if it is encrypted: 

    # stratis pool start pool-uuid --unlock-method <keyring|clevis>

  • Alternatively, use the following command to stop the Stratis pool. This tears down the storage stack but leaves all metadata intact: 

    # stratis pool stop pool-name

Verification steps

  • Use the following command to list all pools on the system: 

    # stratis pool list

  • Use the following command to list all not previously started pools. If the UUID is specified, the command prints detailed information about the pool corresponding to the UUID: 

    # stratis pool list --stopped --uuid UUID

36.1.14. Creating a Stratis file system

Create a Stratis file system on an existing Stratis pool.

Prerequisites

or Creating an encrypted Stratis pool.

Procedure

  1. To create a Stratis file system on a pool, use: 

    # stratis filesystem create --size number-and-unit my-pool my-fs

    where

    number-and-unit
    Specifies the size of a file system. The specification format must follow the standard size specification format for input, that is B, KiB, MiB, GiB, TiB or PiB.
    my-pool
    Specifies the name of the Stratis pool.
    my-fs

    Specifies an arbitrary name for the file system.

    For example:

    Example 36.1. Creating a Stratis file system

    # stratis filesystem create --size 10GiB pool1 filesystem1

Verification steps

  • List file systems withing the pool to check if the Stratis filesystem is created: 

    # stratis fs list my-pool

Additional resources

36.1.15. Mounting a Stratis file system

Mount an existing Stratis file system to access the content.

Prerequisites

Procedure

  • To mount the file system, use the entries that Stratis maintains in the /dev/stratis/ directory: 

    # mount /dev/stratis/my-pool/my-fs mount-point

The file system is now mounted on the mount-point directory and ready to use.

Additional resources

36.1.16. Persistently mounting a Stratis file system

This procedure persistently mounts a Stratis file system so that it is available automatically after booting the system.

Prerequisites

Procedure

  1. Determine the UUID attribute of the file system: 

    $ lsblk --output=UUID /dev/stratis/my-pool/my-fs

    For example:

    Example 36.2. Viewing the UUID of Stratis file system

    $ lsblk --output=UUID /dev/stratis/my-pool/fs1

UUID
a1f0b64a-4ebb-4d4e-9543-b1d79f600283

  2. If the mount point directory does not exist, create it: 

    # mkdir --parents mount-point

  3. As root, edit the /etc/fstab file and add a line for the file system, identified by the UUID. Use xfs as the file system type and add the x-systemd.requires=stratisd.service option.

    For example:

    Example 36.3. The /fs1 mount point in /etc/fstab

    UUID=a1f0b64a-4ebb-4d4e-9543-b1d79f600283 /fs1 xfs defaults,x-systemd.requires=stratisd.service 0 0

  4. Regenerate mount units so that your system registers the new configuration: 

    # systemctl daemon-reload

  5. Try mounting the file system to verify that the configuration works: 

    # mount mount-point

Additional resources

36.1.17. Setting up non-root Stratis filesystems in /etc/fstab using a systemd service

You can manage setting up non-root filesystems in /etc/fstab using a systemd service.

Prerequisites

Procedure

  • For all non-root Stratis filesystems, use: 

    # /dev/stratis/[STRATIS_SYMLINK] [MOUNT_POINT] xfs defaults, x-systemd.requires=stratis-fstab-setup@[POOL_UUID].service,x-systemd.after=stratis-stab-setup@[POOL_UUID].service <dump_value> <fsck_value>

Additional resources

36.2. Extending a Stratis volume with additional block devices

You can attach additional block devices to a Stratis pool to provide more storage capacity for Stratis file systems.

Important

Stratis is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

36.2.1. Components of a Stratis volume

Learn about the components that comprise a Stratis volume.

Externally, Stratis presents the following volume components in the command-line interface and the API:

blockdev
Block devices, such as a disk or a disk partition.
pool

Composed of one or more block devices.

A pool has a fixed total size, equal to the size of the block devices.

The pool contains most Stratis layers, such as the non-volatile data cache using the dm-cache target.

Stratis creates a /dev/stratis/my-pool/ directory for each pool. This directory contains links to devices that represent Stratis file systems in the pool.

filesystem

Each pool can contain one or more file systems, which store files.

File systems are thinly provisioned and do not have a fixed total size. The actual size of a file system grows with the data stored on it. If the size of the data approaches the virtual size of the file system, Stratis grows the thin volume and the file system automatically.

The file systems are formatted with XFS.

Important

Stratis tracks information about file systems created using Stratis that XFS is not aware of, and changes made using XFS do not automatically create updates in Stratis. Users must not reformat or reconfigure XFS file systems that are managed by Stratis.

Stratis creates links to file systems at the /dev/stratis/my-pool/my-fs path.

Note

Stratis uses many Device Mapper devices, which show up in dmsetup listings and the /proc/partitions file. Similarly, the lsblk command output reflects the internal workings and layers of Stratis.

36.2.2. Adding block devices to a Stratis pool

This procedure adds one or more block devices to a Stratis pool to be usable by Stratis file systems.

Prerequisites

  • Stratis is installed. See Installing Stratis.
  • The stratisd service is running.
  • The block devices that you are adding to the Stratis pool are not in use and not mounted.
  • The block devices that you are adding to the Stratis pool are at least 1 GiB in size each.

Procedure

  • To add one or more block devices to the pool, use: 

    # stratis pool add-data my-pool device-1 device-2 device-n

Additional resources

  • stratis(8) man page

36.2.3. Additional resources

36.3. Monitoring Stratis file systems

As a Stratis user, you can view information about Stratis volumes on your system to monitor their state and free space.

Important

Stratis is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

36.3.1. Stratis sizes reported by different utilities

This section explains the difference between Stratis sizes reported by standard utilities such as df and the stratis utility.

Standard Linux utilities such as df report the size of the XFS file system layer on Stratis, which is 1 TiB. This is not useful information, because the actual storage usage of Stratis is less due to thin provisioning, and also because Stratis automatically grows the file system when the XFS layer is close to full.

Important

Regularly monitor the amount of data written to your Stratis file systems, which is reported as the Total Physical Used value. Make sure it does not exceed the Total Physical Size value.

Additional resources

  • stratis(8) man page.

36.3.2. Displaying information about Stratis volumes

This procedure lists statistics about your Stratis volumes, such as the total, used, and free size or file systems and block devices belonging to a pool.

Prerequisites

Procedure

  • To display information about all block devices used for Stratis on your system: 

    # stratis blockdev

Pool Name  Device Node    Physical Size   State  Tier
my-pool    /dev/sdb            9.10 TiB  In-use  Data

  • To display information about all Stratis pools on your system: 

    # stratis pool

Name    Total Physical Size  Total Physical Used
my-pool            9.10 TiB              598 MiB

  • To display information about all Stratis file systems on your system: 

    # stratis filesystem

Pool Name  Name  Used     Created            Device
my-pool    my-fs 546 MiB  Nov 08 2018 08:03  /dev/stratis/my-pool/my-fs

Additional resources

  • stratis(8) man page.

36.3.3. Additional resources

36.4. Using snapshots on Stratis file systems

You can use snapshots on Stratis file systems to capture file system state at arbitrary times and restore it in the future.

Important

Stratis is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

36.4.1. Characteristics of Stratis snapshots

In Stratis, a snapshot is a regular Stratis file system created as a copy of another Stratis file system. The snapshot initially contains the same file content as the original file system, but can change as the snapshot is modified. Whatever changes you make to the snapshot will not be reflected in the original file system.

The current snapshot implementation in Stratis is characterized by the following:

  • A snapshot of a file system is another file system.
  • A snapshot and its origin are not linked in lifetime. A snapshotted file system can live longer than the file system it was created from.
  • A file system does not have to be mounted to create a snapshot from it.
  • Each snapshot uses around half a gigabyte of actual backing storage, which is needed for the XFS log.

36.4.2. Creating a Stratis snapshot

This procedure creates a Stratis file system as a snapshot of an existing Stratis file system.

Prerequisites

Procedure

  • To create a Stratis snapshot, use: 

    # stratis fs snapshot my-pool my-fs my-fs-snapshot

Additional resources

  • stratis(8) man page.

36.4.3. Accessing the content of a Stratis snapshot

This procedure mounts a snapshot of a Stratis file system to make it accessible for read and write operations.

Prerequisites

Procedure

  • To access the snapshot, mount it as a regular file system from the /dev/stratis/my-pool/ directory: 

    # mount /dev/stratis/my-pool/my-fs-snapshot mount-point

Additional resources

36.4.4. Reverting a Stratis file system to a previous snapshot

This procedure reverts the content of a Stratis file system to the state captured in a Stratis snapshot.

Prerequisites

Procedure

  1. Optionally, back up the current state of the file system to be able to access it later: 

    # stratis filesystem snapshot my-pool my-fs my-fs-backup

  2. Unmount and remove the original file system: 

    # umount /dev/stratis/my-pool/my-fs
# stratis filesystem destroy my-pool my-fs

  3. Create a copy of the snapshot under the name of the original file system: 

    # stratis filesystem snapshot my-pool my-fs-snapshot my-fs

  4. Mount the snapshot, which is now accessible with the same name as the original file system: 

    # mount /dev/stratis/my-pool/my-fs mount-point

The content of the file system named my-fs is now identical to the snapshot my-fs-snapshot.

Additional resources

  • stratis(8) man page.

36.4.5. Removing a Stratis snapshot

This procedure removes a Stratis snapshot from a pool. Data on the snapshot are lost.

Prerequisites

Procedure

  1. Unmount the snapshot: 

    # umount /dev/stratis/my-pool/my-fs-snapshot

  2. Destroy the snapshot: 

    # stratis filesystem destroy my-pool my-fs-snapshot

Additional resources

  • stratis(8) man page.

36.4.6. Additional resources

36.5. Removing Stratis file systems

You can remove an existing Stratis file system, or a Stratis pool, by destroying data on them.

Important

Stratis is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.

36.5.1. Components of a Stratis volume

Learn about the components that comprise a Stratis volume.

Externally, Stratis presents the following volume components in the command-line interface and the API:

blockdev
Block devices, such as a disk or a disk partition.
pool

Composed of one or more block devices.

A pool has a fixed total size, equal to the size of the block devices.

The pool contains most Stratis layers, such as the non-volatile data cache using the dm-cache target.

Stratis creates a /dev/stratis/my-pool/ directory for each pool. This directory contains links to devices that represent Stratis file systems in the pool.

filesystem

Each pool can contain one or more file systems, which store files.

File systems are thinly provisioned and do not have a fixed total size. The actual size of a file system grows with the data stored on it. If the size of the data approaches the virtual size of the file system, Stratis grows the thin volume and the file system automatically.

The file systems are formatted with XFS.

Important

Stratis tracks information about file systems created using Stratis that XFS is not aware of, and changes made using XFS do not automatically create updates in Stratis. Users must not reformat or reconfigure XFS file systems that are managed by Stratis.

Stratis creates links to file systems at the /dev/stratis/my-pool/my-fs path.

Note

Stratis uses many Device Mapper devices, which show up in dmsetup listings and the /proc/partitions file. Similarly, the lsblk command output reflects the internal workings and layers of Stratis.

36.5.2. Removing a Stratis file system

This procedure removes an existing Stratis file system. Data stored on it are lost.

Prerequisites

Procedure

  1. Unmount the file system: 

    # umount /dev/stratis/my-pool/my-fs

  2. Destroy the file system: 

    # stratis filesystem destroy my-pool my-fs

  3. Verify that the file system no longer exists: 

    # stratis filesystem list my-pool

Additional resources

  • stratis(8) man page.

36.5.3. Removing a Stratis pool

This procedure removes an existing Stratis pool. Data stored on it are lost.

Prerequisites

Procedure

  1. List file systems on the pool: 

    # stratis filesystem list my-pool

  2. Unmount all file systems on the pool: 

    # umount /dev/stratis/my-pool/my-fs-1 \
         /dev/stratis/my-pool/my-fs-2 \
         /dev/stratis/my-pool/my-fs-n

  3. Destroy the file systems: 

    # stratis filesystem destroy my-pool my-fs-1 my-fs-2

  4. Destroy the pool: 

    # stratis pool destroy my-pool

  5. Verify that the pool no longer exists: 

    # stratis pool list

Additional resources

  • stratis(8) man page.

36.5.4. Additional resources

36.6. Getting started with swap

Use the swap space to provide temporary storage for inactive processes and data, and prevent out-of-memory errors when physical memory is full. The swap space acts as an extension to the physical memory and allows the system to continue running smoothly even when physical memory is exhausted. Note that using swap space can slow down system performance, so optimizing the use of physical memory, before relying on swap space, can be more favorable.

36.6.1. Overview of swap space

Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM.

Swap space is located on hard drives, which have a slower access time than physical memory. Swap space can be a dedicated swap partition (recommended), a swap file, or a combination of swap partitions and swap files.

In years past, the recommended amount of swap space increased linearly with the amount of RAM in the system. However, modern systems often include hundreds of gigabytes of RAM. As a consequence, recommended swap space is considered a function of system memory workload, not system memory.

Adding swap space

The following are the different ways to add a swap space:

Removing swap space

The following are the different ways to remove a swap space:

36.6.3. Extending swap on an LVM2 logical volume

This procedure describes how to extend swap space on an existing LVM2 logical volume. Assuming /dev/VolGroup00/LogVol01 is the volume you want to extend by 2 GB.

Prerequisites

  • You have sufficient disk space.

Procedure

  1. Disable swapping for the associated logical volume: 

    # swapoff -v /dev/VolGroup00/LogVol01

  2. Resize the LVM2 logical volume by 2 GB: 

    # lvresize /dev/VolGroup00/LogVol01 -L +2G

  3. Format the new swap space: 

    # mkswap /dev/VolGroup00/LogVol01

  4. Enable the extended logical volume: 

    # swapon -v /dev/VolGroup00/LogVol01

Verification

  • To test if the swap logical volume was successfully extended and activated, inspect active swap space by using the following command: 

    $ cat /proc/swaps
$ free -h

36.6.4. Creating an LVM2 logical volume for swap

This procedure describes how to create an LVM2 logical volume for swap. Assuming /dev/VolGroup00/LogVol02 is the swap volume you want to add.

Prerequisites

  • You have sufficient disk space.

Procedure

  1. Create the LVM2 logical volume of size 2 GB: 

    # lvcreate VolGroup00 -n LogVol02 -L 2G

  2. Format the new swap space: 

    # mkswap /dev/VolGroup00/LogVol02

  3. Add the following entry to the /etc/fstab file: 

    /dev/VolGroup00/LogVol02 none swap defaults 0 0

  4. Regenerate mount units so that your system registers the new configuration: 

    # systemctl daemon-reload

  5. Activate swap on the logical volume: 

    # swapon -v /dev/VolGroup00/LogVol02

Verification

  • To test if the swap logical volume was successfully created and activated, inspect active swap space by using the following command: 

    $ cat /proc/swaps
$ free -h

36.6.5. Creating a swap file

This procedure describes how to create a swap file.

Prerequisites

  • You have sufficient disk space.

Procedure

  1. Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 64 MB swap file is 65536.

  2. Create an empty file: 

    # dd if=/dev/zero of=/swapfile bs=1024 count=65536

    Replace 65536 with the value equal to the desired block size.

  3. Set up the swap file with the command: 

    # mkswap /swapfile

  4. Change the security of the swap file so it is not world readable. 

    # chmod 0600 /swapfile

  5. Edit the /etc/fstab file with the following entries to enable the swap file at boot time: 

    /swapfile none swap defaults 0 0

    The next time the system boots, it activates the new swap file.

  6. Regenerate mount units so that your system registers the new /etc/fstab configuration: 

    # systemctl daemon-reload

  7. Activate the swap file immediately: 

    # swapon /swapfile

Verification

  • To test if the new swap file was successfully created and activated, inspect active swap space by using the following command: 

    $ cat /proc/swaps
$ free -h

36.6.6. Reducing swap on an LVM2 logical volume

This procedure describes how to reduce swap on an LVM2 logical volume. Assuming /dev/VolGroup00/LogVol01 is the volume you want to reduce.

Procedure

  1. Disable swapping for the associated logical volume: 

    # swapoff -v /dev/VolGroup00/LogVol01

  2. Reduce the LVM2 logical volume by 512 MB: 

    # lvreduce /dev/VolGroup00/LogVol01 -L -512M

  3. Format the new swap space: 

    # mkswap /dev/VolGroup00/LogVol01

  4. Activate swap on the logical volume: 

    # swapon -v /dev/VolGroup00/LogVol01

Verification

  • To test if the swap logical volume was successfully reduced, inspect active swap space by using the following command: 

    $ cat /proc/swaps
$ free -h

36.6.7. Removing an LVM2 logical volume for swap

This procedure describes how to remove an LVM2 logical volume for swap. Assuming /dev/VolGroup00/LogVol02 is the swap volume you want to remove.

Procedure

  1. Disable swapping for the associated logical volume: 

    # swapoff -v /dev/VolGroup00/LogVol02

  2. Remove the LVM2 logical volume: 

    # lvremove /dev/VolGroup00/LogVol02

  3. Remove the following associated entry from the /etc/fstab file: 

    /dev/VolGroup00/LogVol02 none swap defaults 0 0

  4. Regenerate mount units so that your system registers the new configuration: 

    # systemctl daemon-reload

Verification

  • To test if the logical volume was successfully removed, inspect active swap space by using the following command: 

    $ cat /proc/swaps
$ free -h

36.6.8. Removing a swap file

This procedure describes how to remove a swap file.

Procedure

  1. At a shell prompt, execute the following command to disable the swap file, where /swapfile is the swap file: 

    # swapoff -v /swapfile
  2. Remove its entry from the /etc/fstab file accordingly.

  3. Regenerate mount units so that your system registers the new configuration: 

    # systemctl daemon-reload

  4. Remove the actual file: 

    # rm /swapfile
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