Manage storage and filesystems on Azure Linux

Azure Linux virtual machines (VMs) are commonly deployed with ext4 as the root filesystem. Other filesystems, such as xfs and btrfs, are available for extra disks or non-root volumes when your workload requires them.

This article shows you how to identify the filesystem on your Azure Linux system, discover the filesystem packages that are available for installation, use the standard utilities for managing ext4 and other filesystems, and force a filesystem check on the next boot.

Prerequisites

• An Azure Linux system that you can authenticate to with shell access.
• A user account with sudo privileges, which is required to create or repair filesystems, modify partitions, and force a filesystem check on boot.

Identify the root filesystem

Identify the filesystem type that's currently in use for the root volume (/) using the following command:

df -T /

The following example shows typical output on an Azure Linux VM that uses ext4 for the root filesystem:

Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sda2 ext4 30681648 1870824 27231892 7% /

The Type column shows the filesystem type, and the Mounted on column confirms that the filesystem is mounted at /.

Discover available filesystem packages

Azure Linux ships with ext4 support out of the box. To discover other filesystem-related packages that are available for installation, such as xfsprogs and btrfs-progs, use the following command:

dnf search filesystem | grep -Ei "fs|ext4|xfs|btrfs"

The output lists packages whose name or summary mentions a filesystem, which provides a starting point for choosing the right filesystem and tooling for additional disks.

Filesystem management utilities

Azure Linux includes the standard Linux filesystem utilities for creating, inspecting, repairing, and tuning filesystems.

ext4 utilities (e2fsprogs)

The e2fsprogs package provides the standard suite of utilities for managing ext4 filesystems. Key commands include:

• mkfs.ext4: Creates a new ext4 filesystem on a disk or partition.
• fsck.ext4: Checks and repairs the integrity of an ext4 filesystem.
• tune2fs: Adjusts ext4 parameters such as reserved-block percentage and journaling options.

General disk and filesystem utilities

The following utilities work with any filesystem and are useful for managing disks, partitions, and mounts:

• parted: Partition management tool that supports GPT and MBR layouts, including creating and resizing partitions.
• gdisk: Interactive GPT partition table editor.
• lsblk: Lists block devices and their relationships in a tree view.
• blkid: Displays the filesystem type and UUID for each block device.
• df: Shows disk space usage for mounted filesystems.
• du: Shows disk space usage for files and directories.
• mount: Mounts a filesystem at a specified mount point.
• umount: Unmounts a previously mounted filesystem.
• fsck: Generic filesystem check wrapper that calls the appropriate filesystem-specific checker, such as fsck.ext4.

Force a filesystem check on the next boot

If you need to recover from suspected corruption or verify the integrity of the root filesystem, you can ask the system to run fsck on / the next time it boots before the root filesystem is mounted.

Force a filesystem check at the next boot using the following commands:

sudo touch /forcefsck
sudo reboot

When the system boots, it detects the /forcefsck flag file, runs fsck against the root filesystem, and then removes the flag file automatically. This is useful for recovering from suspected corruption or for verifying filesystem integrity after an unexpected shutdown.

Related content

For more information, see the following upstream resources:

• ext4 filesystem documentation: Upstream Linux kernel documentation for the ext4 filesystem, including features, tuning options, and on-disk format.