Linux Disk, Mount & Filesystem Errors
Linux disk and filesystem failures grouped in one place: a full disk, mounts that fail with the wrong fs-type or a bad superblock, an fstab typo that drops you into emergency mode, a device gone read-only, or a busy umount. Each guide opens with the fix and the `df`, `mount`, `fsck`, and `lsblk` commands to prove it. Pick your error below, or paste it into the assistant.
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Every guide in this cluster
14 guides-
'No space left on device' ENOSPC Disk and Inode Exhaustion
Fix the Linux 'No space left on device' (ENOSPC) error: diagnose full filesystems, inode exhaustion, deleted-but-open files, reserved blocks, and runaway logs.
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'No space left on device' — Fix a Full Disk, Inodes, and Open Files
Fix 'No space left on device' on a full Linux filesystem: reclaim bytes, diagnose exhausted inodes with df -i, and free deleted-but-open files held open.
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'mount: wrong fs type, bad option, bad superblock' — Fix Failed Mounts
Fix Linux mount failures: wrong fs type, bad superblock, missing helper program, device not found, and broken /etc/fstab entries with real diagnostic commands.
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mount: wrong fs type, bad option, bad superblock — Cause, Fix, and Troubleshooting Guide
How to fix the Linux 'mount: wrong fs type, bad option, bad superblock' error: diagnose filesystem type mismatches, corrupt superblocks, missing modules, and bad fstab options.
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'Buffer I/O error on dev sda' — Recover From Read Errors and Bad Blocks
Diagnose Linux disk read I/O errors and 'Buffer I/O error on dev' bad blocks using SMART, badblocks, and ddrescue, then recover data safely and remap sectors.
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'I/O error' on Write — Diagnose a Failing Disk and Bad Sectors
Diagnose disk write I/O errors (blk_update_request, write error: Input/output error) from failing disks, bad sectors, dying SSDs, or bad cabling using SMART.
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'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)' — Rebuild Initramfs and Recover
Resolve the boot-time kernel panic VFS unable to mount root fs. Rebuild initramfs, fix GRUB root= parameters, repair fstab, and recover using rescue mode.
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'Read-only file system' on Write-Protected Media — Clear the Protection
Fix write-protected disks, USB, and SD cards on Linux: physical switches, blockdev/hdparm read-only flags, ro mounts, and worn flash that forces read-only mode.
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'swapon: swapon failed: Invalid argument' — fix the swap file or partition
Fix 'swapon failed: Invalid argument': diagnose an unformatted, wrong-size, holey, or CoW swap file versus a mislabeled partition, rebuild it correctly with mkswap, and enable swap reliably.
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'umount: target is busy' — Free a Busy Mountpoint
Fix 'umount: target is busy' on Linux: find the processes, open files, and bind mounts holding a mountpoint, and unmount cleanly with fuser and lsof.
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'wrong fs type, bad option, bad superblock' — Identify Filesystem and Fix Mount
Fix mount failures caused by wrong filesystem type, corrupt superblocks, missing helpers, or unopened LUKS/LVM devices using blkid, fsck, and dmesg.
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'You are in emergency mode' — Repair a Broken /etc/fstab Boot
Fix 'You are in emergency mode' on Linux after a bad /etc/fstab entry: read journalctl -b, identify the failed mount, comment or add nofail, and restore a clean systemd boot.
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'Dependency failed for /<mountpoint>' — Cause, Fix, and Troubleshooting Guide
How to fix the Linux 'Dependency failed for /<mountpoint>' systemd error: diagnose failed mount units, fstab entries, RequiresMountsFor, and nofail options to boot cleanly.
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Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block — Cause, Fix, and Troubleshooting Guide
How to fix the Linux 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block' error: repair a missing initramfs, wrong root=, or missing storage driver.
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Frequently asked questions
"No space left on device" but df shows free space — why?
df -h shows block usage; run df -i to see inode usage. Millions of tiny files (session caches, mail spools) exhaust inodes while leaving blocks free. See No space left on device.A bad mount dropped my server into emergency mode — how do I recover?
/etc/fstab entry fails at boot and systemd drops to emergency mode. Boot single-user or from rescue media, comment out or fix the offending line, then mount -a to test before rebooting. See fstab emergency mode.What does "wrong fs type, bad option, bad superblock" mean?
blkid, and if the superblock is bad, mount from a backup superblock and run fsck. See bad superblock.