Linux supports many filesystem implementations with different on-disk formats, network protocols, consistency models, features, and operational tools. The right choice depends on distribution support, workload, recovery requirements, storage topology, and administrator experience.
The Filesystem · Lesson 2
Filesystem Types
Learn how Linux VFS presents local, network, and virtual filesystems through one interface.
The Virtual Filesystem Layer
The kernel's Virtual Filesystem layer, or VFS, provides common operations such as open, read, write, rename, and permission checks. Filesystem implementations connect those operations to their own data structures and backing stores.
This lets one process access ext4, XFS, NFS, tmpfs, and procfs through a shared pathname and file-descriptor model. It does not make every filesystem feature or behavior identical: case sensitivity, locking, permissions, rename guarantees, extended attributes, and error handling can differ.
What is the primary role of Linux VFS?
Journaling and Crash Consistency
A journaling filesystem records selected updates in a journal so it can replay or discard incomplete transactions after a crash. Journaling is primarily about restoring filesystem structural consistency more quickly than a full scan.
It does not guarantee that the latest application data survived, that multi-file application transactions are valid, or that storage hardware honored every completed write. Filesystems offer different data modes and ordering guarantees, while applications must use appropriate flush and atomic-update patterns. A journal is not a backup and does not protect against deletion, malware, or device failure.
What does filesystem journaling primarily help recover after a crash?
Common Local Filesystems
- ext4 is a mature journaling filesystem widely supported by Linux distributions and recovery tools.
- XFS is a scalable journaling filesystem commonly chosen for large filesystems and parallel I/O workloads.
- Btrfs is a copy-on-write filesystem with checksums, subvolumes, snapshots, and integrated multi-device features.
Features require operational context. A Btrfs snapshot initially shares storage with its source and is not an independent backup when it remains on the same failing device. XFS and ext4 have different grow, shrink, repair, and tuning capabilities. Confirm support for the installed kernel, boot environment, and recovery tooling before choosing or changing a root filesystem.
Why is a Btrfs snapshot on the same device not a complete backup?
Interoperability, Network, and Virtual Filesystems
Linux can mount interoperability formats such as FAT variants, exFAT, and NTFS, but their Unix ownership, permissions, links, and filename semantics differ. Mount options and driver implementation determine how Linux presents missing features.
Network filesystems such as NFS and SMB depend on a server and network protocol, with distinct caching and identity rules. Virtual filesystems such as tmpfs, procfs, and sysfs do not use a normal persistent disk format: tmpfs stores volatile data in memory-backed pages, while procfs and sysfs expose kernel interfaces.
Which description best fits procfs?
Discovering Active Types
Show mounted filesystem types with:
$ findmnt -o TARGET,SOURCE,FSTYPE,OPTIONS
Alternative views include df -T for mounted space accounting, lsblk -f for block devices and detected filesystem signatures, and /proc/filesystems for types supported or known by the running kernel. These answer different questions; an unmounted filesystem will not appear in an ordinary mounted-filesystem listing.
Which command directly lists mounted targets with source, type, and options in the shown lesson?
Use Manage Linux Partitions and Filesystems on disposable storage to compare types, mount options, and discovery views.
Lesson complete
You finished Filesystem Types
You can now compare filesystem categories without assuming identical semantics.
Relate VFS to common operations across implementations.
Treat journaling as crash-consistency support, not backup.
Compare ext4, XFS, and Btrfs by supported operations and workload.
Distinguish local disk, network, interoperability, and virtual filesystems.
Use mount and block-device tools to answer different inventory questions.
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