tune2fs

**tune2fs** is a command-line utility in Linux used to adjust various tunable filesystem parameters on ext2, ext3, and ext4 filesystems. This tool is part of the e2fsprogs package and is commonly used by system administrators to modify filesystem attributes after the filesystem has been created.

Overview of tune2fs

Basic Syntax

tune2fs [options] <device>

  • <device>: The device or partition containing the filesystem to be modified (e.g., /dev/sda1).

Commonly Used Options

Adjusting Filesystem Parameters

  • -l : Lists the current parameters of the filesystem.

  • -c max-mount-counts : Sets the number of times the filesystem can be mounted before a consistency check is forced.

  • -i interval-between-checks[d|m|w] : Sets the interval between forced filesystem checks.

  • -r reserved-blocks-count : Sets the number of reserved filesystem blocks.

  • -m reserved-blocks-percentage : Sets the percentage of the filesystem blocks reserved for the super-user.

  • -e errors-behavior : Sets the behavior when an error is detected (continue, remount-ro, or panic).

  • -L volume-label : Sets the volume label for the filesystem.

  • -U UUID : Sets the universally unique identifier (UUID) for the filesystem.

  • -o mount-options : Sets default mount options for the filesystem.

  • -E extended-options : Sets extended options like stripe, resize, etc.

Example Usage

Listing Filesystem Parameters

To list all current parameters of the filesystem on /dev/sda1:

sudo tune2fs -l /dev/sda1

Setting Maximum Mount Count

To set the maximum mount count to 50 for /dev/sda1:

sudo tune2fs -c 50 /dev/sda1

Setting Interval Between Checks

To set the interval between forced filesystem checks to 30 days:

sudo tune2fs -i 30d /dev/sda1

Setting Reserved Blocks Count

To set the number of reserved blocks to 5000:

sudo tune2fs -r 5000 /dev/sda1

Setting Reserved Blocks Percentage

To set the reserved blocks percentage to 1%:

sudo tune2fs -m 1 /dev/sda1

Setting Error Behavior

To set the filesystem to remount as read-only on error:

sudo tune2fs -e remount-ro /dev/sda1

Setting Volume Label

To set the volume label to "MY_LABEL":

sudo tune2fs -L MY_LABEL /dev/sda1

Setting UUID

To set a new UUID for the filesystem:

sudo tune2fs -U random /dev/sda1

Setting Default Mount Options

To set default mount options to noatime and nodiratime:

sudo tune2fs -o noatime,nodiratime /dev/sda1

Setting Extended Options

To set an extended option such as resize (resize inode size):

sudo tune2fs -E resize=256 /dev/sda1

Advanced Examples

Reducing Reserved Space

By default, ext2/3/4 filesystems reserve 5% of the space for the root user. This is useful on root filesystems to avoid running out of space completely, but on large storage partitions, you might want to reduce this:

To set the reserved blocks percentage to 1% on a large storage partition:

sudo tune2fs -m 1 /dev/sdb1

Setting Filesystem Check Intervals

You might want to ensure that your filesystem is checked for consistency every 3 months:

sudo tune2fs -i 3m /dev/sda1

Modifying Error Behavior

Setting the filesystem to panic on error can be useful for critical systems where data integrity is paramount:

sudo tune2fs -e panic /dev/sda1

Summary

**tune2fs** is a versatile tool that allows administrators to optimize and control various aspects of ext2, ext3, and ext4 filesystems. Understanding and using tune2fs can help in maintaining filesystem integrity, optimizing performance, and ensuring efficient use of disk space.

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