# Major changes:
🔴 Bcachefs → Removed from mainline kernel (Sept. 2025)
🔴 ReiserFS → Permanently removed (Kernel 6.13)
🟠 ext3 → Driver removed, mounted via ext4 only
🟢 btrfs → Consolidated as a modern alternative
🟢 XFS V5 → Mandatory format, V4 deprecated
# Impact: yesterday's choices are no longer valid today

# 1. Kernel Status
Current → Integrated and maintained in the mainline kernel
External → DKMS module / out-of-tree (e.g., ZFS, APFS)
Obsolete → Driver present but deprecated
Removed → Code removed from kernel
# 2. Intrinsic Security Level
🔐 Very High : data+metadata checksums, self-healing
🛡️ High : metadata checksums, robust journaling
🔒 Medium : basic journaling, no data checksums
⚠️ Low : no journaling, known vulnerabilities
# 3. Migration Strategy
→ Exact commands, prerequisites, risks, rollback

# For each filesystem:
✓ Updated kernel status (6.18+)
✓ Updated technical description
✓ EXACT security table (Checksums/Self-healing/Isolation/Level)
✓ Copyable audit commands
✓ Expected result for validation
✓ Usage recommendation
# Navigation:
→ Click an item in the left menu
→ Commands are directly copyable
→ Use the floating table of contents (top right)

# Detect mounted ReiserFS
df -T | grep reiserfs
# Prepare btrfs migration (unmounted partition)
sudo btrfs-convert /dev/sdXY
# Verify conversion
sudo btrfs filesystem show /dev/sdXY

# Detect ext3
df -T | grep ext3
# Mount ext3 via ext4 driver (automatic)
grep ext3 /etc/fstab # replace with ext4
# Convert to ext4 if needed
sudo tune2fs -O extents,uninit_bg,dir_index /dev/sdXY

# Detect ext2
df -T | grep ext2
# Move ext2→ext3 (add journal)
sudo tune2fs -j /dev/sdXY
# Then migrate to ext4
sudo tune2fs -O extents,uninit_bg,dir_index /dev/sdXY

# Detect JFS
df -T | grep jfs
# Verify integrity
sudo jfs_fsck -n /dev/sdXY
# Migration: backup + format ext4/btrfs
sudo mkfs.ext4 /dev/sdXY

# Detect minix
df -T | grep minix
# Urgent migration
sudo umount /dev/sdXYsudo mkfs.ext4 /dev/sdXY

# Verify bcachefs module loaded
lsmod | grep bcachefs
# Installed DKMS version
dkms status | grep bcachefs
# Audit mount
mount | grep bcachefs

# Verify ntfs3 driver (kernel 5.15+)
lsmod | grep ntfs3
# Mount NTFS partition
sudo mount -t ntfs3 /dev/sdXY /mnt/ntfs
# FUSE Alternative (ntfs-3g)
sudo mount -t ntfs-3g /dev/sdXY /mnt/ntfs

# Verify exfat module
lsmod | grep exfat
# Mount
sudo mount -t exfat /dev/sdXY /mnt/exfat
# Verify integrity
sudo fsck.exfat /dev/sdXY

# Install apfs-fuse (Debian/Ubuntu)
sudo apt install apfs-fuse
# Mount APFS partition (read-only)
sudo apfs-fuse -o allow_other /dev/sdXY /mnt/apfs
# Verify mount
mount | grep apfs

# Detect FAT32
df -T | grep vfat
# Mount with security options
sudo mount -t vfat /dev/sdXY /mnt/usb -o uid=1000,gid=1000,umask=077
# Verify
sudo fsck.vfat -n /dev/sdXY

# NFS: active exports
exportfs -v
# NFS mounts client-side
mount | grep nfs
# Service status
systemctl status nfs-server
# Verify NFSv4 version
nfsstat -m

# SMB: mounted shares
mount | grep cifs
# Verify SMB encryption
grep -i encrypt /etc/samba/smb.conf
# Test connection
smbclient -L //server/share -U user

# CephFS client status
ceph status
# CephFS mount
mount -t ceph mon1:6789,mon2:6789:/ /mnt/ceph -o name=admin,secretfile=/etc/ceph/admin.secret
# Verify integrity
ceph fs status

# GlusterFS status
gluster volume status
# Volume information
gluster volume info
# Client mount
mount -t glusterfs server:/volname /mnt/gluster

# /tmp mount options (tmpfs)
findmnt -o OPTIONS /tmp
# Harden tmpfs in /etc/fstab:
# tmpfs /tmp tmpfs defaults,noexec,nosuid,nodev,mode=1777 0 0
# Verify usage
df -h /tmp

# /proc mounted with hidepid?
grep proc /proc/mounts
# Harden in /etc/fstab:
# proc /proc proc defaults,hidepid=2 0 0
# Verify
mount | grep proc

# Verify sysfs mount
mount | grep sysfs
# Explore hardware info
ls /sys/class/net/
# Verify permissions
ls -la /sys/

# Verify if debugfs is mounted
mount | grep debugfs
# Disable in production
sudo umount /sys/kernel/debug
# Prevent auto-mount
# Remove any debugfs line from /etc/fstab

# Verify configfs mount
mount | grep configfs
# Explore
ls /sys/kernel/config/

# Verify configured huge pages
cat /proc/sys/vm/nr_hugepages
# Mount hugetlbfs
mount -t hugetlbfs none /dev/hugepages
# Verify mount
mount | grep hugetlbfs

# Detect mounted overlayfs
findmnt -o TARGET,FSTYPE | grep overlay
# Verify layers (lower/upper)
mount | grep overlay
# Docker usage
docker info | grep -i 'storage driver'

# Verify if ramfs is used
mount | grep ramfs
# Prefer tmpfs instead:
# /etc/fstab : tmpfs /mnt/ram tmpfs size=512M,mode=0700 0 0
# If ramfs detected → migrate to tmpfs
sudo umount /mnt/ramfssudo mount -t tmpfs -o size=512M tmpfs /mnt/ram

# Detect cramfs
findmnt -o TARGET,FSTYPE | grep cramfs
# Migrate to SquashFS (better compression, checksums)
# Recreate image with mksquashfssudo mksquashfs /source/dir new-image.squashfs -comp zstd
# Mount new image
sudo mount -t squashfs new-image.squashfs /mnt/sqfs -o loop

# Detect EROFS
findmnt -o TARGET,FSTYPE | grep erofs
# Verify integrity
fsck.erofs -n /dev/sdXY

# Detect SquashFS
findmnt -o TARGET,FSTYPE | grep squashfs
# Verify image integrity
unsquashfs -l /path/to/image.squashfs | head -10
# Mount
sudo mount -t squashfs image.squashfs /mnt/sqfs -o loop

# Detect ISO9660
findmnt -o TARGET,FSTYPE | grep iso9660
# Mount ISO image
sudo mount -t iso9660 -o loop image.iso /mnt/iso
# Verify
mount | grep iso9660

# Detect UDF
findmnt -o TARGET,FSTYPE | grep udf
# Mount
sudo mount -t udf /dev/sr0 /mnt/udf
# Verify
mount | grep udf

# 1. Full Inventory
lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,UUID
# 2. Critical Mount Options
findmnt -o TARGET,OPTIONS | grep -E 'noexec|nosuid|nodev'
# 3. Filesystems with checksums (security)
for fs in $(df -T | tail -n+2 | awk '{print $2}' | sort -u); doecho -n "$fs: "case $fs inbtrfs|xfs|zfs) echo "check sums" ;;ext4) echo "~ metadata only" ;;*) echo "none" ;;esacdone
# 4. Detect mounted obsolete filesystems
df -T | grep -E 'reiserfs|ext[23]|jfs|minix|cramfs|ramfs' && echo "Migration required"

# btrfs: scrub (data+metadata checksums)
sudo btrfs scrub status /mountpoint
# XFS: metadata verification (V5 format)
sudo xfs_repair -n /dev/sdXY 2>&1 | grep -i error
# ZFS: full scrub
sudo zpool status -t tank
# ext4: preventive fsck (unmounted)
sudo fsck.ext4 -n /dev/sdXY
# F2FS: verification
sudo fsck.f2fs -n /dev/sdXY

# /tmp: noexec,nosuid,nodev
findmnt -o OPTIONS /tmp | grep -q 'noexec' && echo "/tmp secure" || echo "/tmp needs hardening"
# /dev/shm: noexec,nosuid,nodev
findmnt -o OPTIONS /dev/shm | grep -q 'noexec' && echo "/dev/shm secure" || echo "/dev/shm needs hardening"
# /proc: hidepid
grep 'hidepid' /proc/mounts && echo "hidepid active" || echo "hidepid inactive"
# debugfs: must NOT be mounted
mount | grep debugfs && echo "debugfs mounted!" || echo "debugfs absent"

# PREREQUISITE: full backup!
# 1. Unmount ReiserFS partition
sudo umount /dev/sdXY
# 2. In-place conversion to btrfs
sudo btrfs-convert /dev/sdXY
# 3. Mount the new btrfs
sudo mount -t btrfs /dev/sdXY /mnt/new
# 4. Verify and delete rollback image
sudo btrfs subvolume list /mnt/newsudo btrfs subvolume delete /mnt/new/reiserfs_saved

# Step 1: ext3 → ext4 (direct mount)
# /etc/fstab : replace ext3 with ext4, then reboot
# Step 2: ext4 → btrfs (conversion)
sudo umount /dev/sdXYsudo btrfs-convert /dev/sdXYsudo mount -t btrfs /dev/sdXY /mnt/btrfs
# Enable compression (optional)
sudo btrfs property set -ts /mnt/btrfs compression zstd

# ext2 → ext3 (add journal)
sudo tune2fs -j /dev/sdXY
# ext3 → ext4 (extensions, dir_index)
sudo tune2fs -O extents,uninit_bg,dir_index /dev/sdXYsudo e2fsck -f /dev/sdXY
# ext4 → btrfs (conversion)
sudo umount /dev/sdXYsudo btrfs-convert /dev/sdXY

# 1. Full Backup
sudo rsync -aAXv /mnt/old/ /mnt/backup/
# 2. Format to ext4 (or rebuild as SquashFS)
sudo umount /dev/sdXYsudo mkfs.ext4 /dev/sdXY
# 3. Restore
sudo mount /dev/sdXY /mnt/newsudo rsync -aAXv /mnt/backup/ /mnt/new/
# Alternative cramfs → SquashFS:
sudo mksquashfs /mnt/cramfs-contents new.squashfs -comp zstd

# Full reference:
Title : "Linux File Systems Explained: Ext4 Vs Btrfs Vs XFS"
Source : Eagleeyet
Date : January 2026
URL : eagleeyet.net/blog/btrfs-xfs-zfs
# Key points:
→ Sequential and random I/O benchmarks
→ SSD vs HDD performance
→ Production stability (user feedback)
→ Recommendations by scenario (desktop/server/NAS)

# Full reference:
Title : "OpenZFS Release 2.4.1"
Source : OpenZFS Official Documentation
Date : February 2026
URL : openzfs.org/wiki/
# Key points:
→ Compatibility with kernels 4.18 to 6.18
→ RAIDZ expansion (major feature)
→ CVE security fixes
→ Improved NVMe performance
→ Updated DKMS support

# Full reference:
Title : "Key Linux Features Boosting Security Measures for 2026"
Source : LinuxSecurity.com
Date : November 2025
URL : linuxsecurity.com/
# Key points:
→ Impact of FS checksums on security
→ Integrity Measurement Architecture (IMA)
→ Filesystem-level encryption (fscrypt)
→ Integrity controls and corruption detection
→ Hardening recommendations by FS type

# Recommended verification method:
Step 1 → Consult primary source (LWN.net / mailing list)
Step 2 → Check official project website
Step 3 → Cross-check with independent technical media
Step 4 → Test in isolated environment before production
# Example: verifying bcachefs status
1. LWN.net → removal decision
2. kernel.org → status in mainline tree
3. Linux Journal → impact analysis
4. Isolated VM test → verify DKMS behavior

# Article reference:
Title : "OS Security Panorama 2026: Linux, Windows, macOS, BSD"
URL : safeitexperts.com/2026/04/en/complete-os-security-guide-2026.html
# Link with this guide:
→ ext4/XFS/btrfs → Linux filesystems (this guide)
→ NTFS/ReFS → Windows filesystems (comparison)
→ APFS → macOS filesystem (mentioned here)
→ ZFS → common to BSD/Solaris/Linux (OpenZFS)
→ 2026 production table → global context

# Article reference:
Title : "Linux Kernels 2025: Complete Analysis"
URL : safeitexperts.com/en/2026/04/linux-kernels-2025-complete-analysis.html
# Direct link with this guide:
→ Critical CVEs → filesystem vulnerabilities
→ Bcachefs removal → kernel 6.18 removal (this guide)
→ dm-pcache → impact on cached FS
→ Apple Silicon M2 → APFS/FS compatibility
→ Kernel timeline → plan migrations

# Article reference:
Title : "Computer under Linux, Windows, ChromeOS, macOS stolen: security guide"
URL : safeitexperts.com/en/2025/11/computer-under-linux-windows-chromeos-macos-stolen-security-guide.html
# Application to FS migrations:
→ Encryption at rest → protects data during migration
→ Risk analysis → before changing filesystem
→ Recovery strategies → rollback procedures
→ Advanced protection → complements FS hardening

# Access to complete category:
URL : safeitexperts.com/search/security/
# Category content:
→ Security audit guides (filesystems, network, SSH)
→ Hardening tutorials (SELinux, firewall, LUKS)
→ CVE and vulnerability analysis
→ Secure migration methodologies
→ Security monitoring and supervision
# Navigation:
→ Articles sorted by date (newest first)
→ Tags to filter by theme
→ Internal links between related articles