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Chapter 16. Mounting file systems

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As a system administrator, you can mount file systems on your system to access data on them.

16.1. The Linux mount mechanism

These are the basic concepts of mounting file systems on Linux.

On Linux, UNIX, and similar operating systems, file systems on different partitions and removable devices (CDs, DVDs, or USB flash drives for example) can be attached to a certain point (the mount point) in the directory tree, and then detached again. While a file system is mounted on a directory, the original content of the directory is not accessible.

Note that Linux does not prevent you from mounting a file system to a directory with a file system already attached to it.

When mounting, you can identify the device by:

  • a universally unique identifier (UUID): for example, UUID=34795a28-ca6d-4fd8-a347-73671d0c19cb
  • a volume label: for example, LABEL=home
  • a full path to a non-persistent block device: for example, /dev/sda3

When you mount a file system using the mount command without all required information, that is without the device name, the target directory, or the file system type, the mount utility reads the content of the /etc/fstab file to check if the given file system is listed there. The /etc/fstab file contains a list of device names and the directories in which the selected file systems are set to be mounted as well as the file system type and mount options. Therefore, when mounting a file system that is specified in /etc/fstab, the following command syntax is sufficient:

  • Mounting by the mount point:

    # mount directory
  • Mounting by the block device:

    # mount device

Additional resources

16.2. Listing currently mounted file systems

List all currently mounted file systems on the command line by using the findmnt utility.

Procedure

  • To list all mounted file systems, use the findmnt utility:

    $ findmnt
  • To limit the listed file systems only to a certain file system type, add the --types option:

    $ findmnt --types fs-type

    For example:

    Example 16.1. Listing only XFS file systems

    $ findmnt --types xfs
    
    TARGET  SOURCE                                                FSTYPE OPTIONS
    /       /dev/mapper/luks-5564ed00-6aac-4406-bfb4-c59bf5de48b5 xfs    rw,relatime
    ├─/boot /dev/sda1                                             xfs    rw,relatime
    └─/home /dev/mapper/luks-9d185660-7537-414d-b727-d92ea036051e xfs    rw,relatime

Additional resources

  • findmnt(8) man page on your system

16.3. Mounting a file system with mount

Mount a file system by using the mount utility.

Prerequisites

  • Verify that no file system is already mounted on your chosen mount point:

    $ findmnt mount-point

Procedure

  1. To attach a certain file system, use the mount utility:

    # mount device mount-point

    Example 16.2. Mounting an XFS file system

    For example, to mount a local XFS file system identified by UUID:

    # mount UUID=ea74bbec-536d-490c-b8d9-5b40bbd7545b /mnt/data
  2. If mount cannot recognize the file system type automatically, specify it using the --types option:

    # mount --types type device mount-point

    Example 16.3. Mounting an NFS file system

    For example, to mount a remote NFS file system:

    # mount --types nfs4 host:/remote-export /mnt/nfs

Additional resources

  • mount(8) man page on your system

16.4. Moving a mount point

Change the mount point of a mounted file system to a different directory by using the mount utility.

Procedure

  1. To change the directory in which a file system is mounted:

    # mount --move old-directory new-directory

    Example 16.4. Moving a home file system

    For example, to move the file system mounted in the /mnt/userdirs/ directory to the /home/ mount point:

    # mount --move /mnt/userdirs /home
  2. Verify that the file system has been moved as expected:

    $ findmnt
    $ ls old-directory
    $ ls new-directory

Additional resources

  • mount(8) man page on your system

16.5. Unmounting a file system with umount

Unmount a file system by using the umount utility.

Procedure

  1. Try unmounting the file system using either of the following commands:

    • By mount point:

      # umount mount-point
    • By device:

      # umount device

    If the command fails with an error similar to the following, it means that the file system is in use because of a process is using resources on it:

    umount: /run/media/user/FlashDrive: target is busy.
  2. If the file system is in use, use the fuser utility to determine which processes are accessing it. For example:

    $ fuser --mount /run/media/user/FlashDrive
    
    /run/media/user/FlashDrive: 18351

    Afterwards, stop the processes using the file system and try unmounting it again.

16.6. Mounting and unmounting file systems in the web console

To be able to use partitions on RHEL systems, you need to mount a file system on the partition as a device.

Note

You also can unmount a file system and the RHEL system will stop using it. Unmounting the file system enables you to delete, remove, or re-format devices.

Prerequisites

  • The cockpit-storaged package is installed on your system.
  • You have installed the RHEL 8 web console.

    For instructions, see Installing and enabling the web console.

  • If you want to unmount a file system, ensure that the system does not use any file, service, or application stored in the partition.

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Click the Storage tab.
  3. In the Storage table, select a volume from which you want to delete the partition.
  4. In the GPT partitions section, click the menu button, next to the partition whose file system you want to mount or unmount.
  5. Click Mount or Unmount.

16.7. Common mount options

The following table lists the most common options of the mount utility. You can apply these mount options using the following syntax:

# mount --options option1,option2,option3 device mount-point
Table 16.1. Common mount options
OptionDescription

async

Enables asynchronous input and output operations on the file system.

auto

Enables the file system to be mounted automatically using the mount -a command.

defaults

Provides an alias for the async,auto,dev,exec,nouser,rw,suid options.

exec

Allows the execution of binary files on the particular file system.

loop

Mounts an image as a loop device.

noauto

Default behavior disables the automatic mount of the file system using the mount -a command.

noexec

Disallows the execution of binary files on the particular file system.

nouser

Disallows an ordinary user (that is, other than root) to mount and unmount the file system.

remount

Remounts the file system in case it is already mounted.

ro

Mounts the file system for reading only.

rw

Mounts the file system for both reading and writing.

user

Allows an ordinary user (that is, other than root) to mount and unmount the file system.

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