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Chapter 30. Getting started with an ext3 file system

As a system administrator, you can create, mount, resize, backup, and restore an ext3 file system. The ext3 file system is essentially an enhanced version of the ext2 file system.

30.1. Features of an ext3 file system

Following are the features of an ext3 file system:

  • Availability: After an unexpected power failure or system crash, file system check is not required due to the journaling provided. The default journal size takes about a second to recover, depending on the speed of the hardware

    Note

    The only supported journaling mode in ext3 is data=ordered (default). For more information, see Is the EXT journaling option "data=writeback" supported in RHEL? Knowledgebase article.

  • Data Integrity: The ext3 file system prevents loss of data integrity during an unexpected power failure or system crash.
  • Speed: Despite writing some data more than once, ext3 has a higher throughput in most cases than ext2 because ext3’s journaling optimizes hard drive head motion.
  • Easy Transition: It is easy to migrate from ext2 to ext3 and gain the benefits of a robust journaling file system without reformatting.

Additional resources

  • ext3 man page.

30.2. Creating an ext3 file system

As a system administrator, you can create an ext3 file system on a block device using mkfs.ext3 command.

Prerequisites

.

+ Alternatively, use an LVM or MD volume.

Procedure

  1. To create an ext3 file system:

    • For a regular-partition device, an LVM volume, an MD volume, or a similar device, use the following command: 

      # mkfs.ext3 /dev/block_device

      Replace /dev/block_device with the path to a block device.

      For example, /dev/sdb1, /dev/disk/by-uuid/05e99ec8-def1-4a5e-8a9d-5945339ceb2a, or /dev/my-volgroup/my-lv. In general, the default options are optimal for most usage scenarios.

    • For striped block devices (for example, RAID5 arrays), the stripe geometry can be specified at the time of file system creation. Using proper stripe geometry enhances the performance of an ext3 file system. For example, to create a file system with a 64k stride (that is, 16 x 4096) on a 4k-block file system, use the following command: 

      # mkfs.ext3 -E stride=16,stripe-width=64 /dev/block_device

      In the given example:

      • stride=value: Specifies the RAID chunk size
      • stripe-width=value: Specifies the number of data disks in a RAID device, or the number of stripe units in the stripe.
    Note

    • To specify a UUID when creating a file system: 

      # mkfs.ext3 -U UUID /dev/block_device

      Replace UUID with the UUID you want to set: for example, 7cd65de3-e0be-41d9-b66d-96d749c02da7.

      Replace /dev/block_device with the path to an ext3 file system to have the UUID added to it: for example, /dev/sda8.

    • To specify a label when creating a file system: 

      # mkfs.ext3 -L label-name /dev/block_device

  2. To view the created ext3 file system: 

    # blkid

Additional resources

  • ext3 man page.
  • mkfs.ext3 man page.

30.3. Mounting an ext3 file system

As a system administrator, you can mount an ext3 file system using the mount utility.

Prerequisites

Procedure

  1. To create a mount point to mount the file system: 

    # mkdir /mount/point

    Replace /mount/point with the directory name where mount point of the partition must be created.

  2. To mount an ext3 file system:

    • To mount an ext3 file system with no extra options: 

      # mount /dev/block_device /mount/point
    • To mount the file system persistently, see Persistently mounting file systems.

  3. To view the mounted file system: 

    # df -h

Additional resources

30.4. Resizing an ext3 file system

As a system administrator, you can resize an ext3 file system using the resize2fs utility. The resize2fs utility reads the size in units of file system block size, unless a suffix indicating a specific unit is used. The following suffixes indicate specific units:

  • s (sectors) - 512 byte sectors
  • K (kilobytes) - 1,024 bytes
  • M (megabytes) - 1,048,576 bytes
  • G (gigabytes) - 1,073,741,824 bytes
  • T (terabytes) - 1,099,511,627,776 bytes

Prerequisites

  • An ext3 file system. For information about creating an ext3 file system, see Creating an ext3 file system.
  • An underlying block device of an appropriate size to hold the file system after resizing.

Procedure

  1. To resize an ext3 file system, take the following steps:

    • To shrink and grow the size of an unmounted ext3 file system: 

      # umount /dev/block_device
# e2fsck -f /dev/block_device
# resize2fs /dev/block_device size

      Replace /dev/block_device with the path to the block device, for example /dev/sdb1.

      Replace size with the required resize value using s, K, M, G, and T suffixes.

    • An ext3 file system may be grown while mounted using the resize2fs command: 

      # resize2fs /mount/device size
      Note

      The size parameter is optional (and often redundant) when expanding. The resize2fs automatically expands to fill the available space of the container, usually a logical volume or partition.

  2. To view the resized file system: 

    # df -h

Additional resources

  • resize2fs man page.
  • e2fsck man page.
  • ext3 man page.