e2fsck: file system check

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Partitions

To be safe a regular file system check should be regularly performed on every partition of every hard disk that you own.

Before using e2fsck, the partition should be unmounted. This is easy to do with an external drive used for backup, but it requires a special procedure when you want to check the partition where root (/) /usr or /home reside. Thus, we shall consider those scenarios separately.

External device

Internal device (/, /usr, /home)

Interactive

# e2fsck -vfFC0 /dev/sdc1                      
e2fsck 1.41.9 (22-Aug-2009)                                   
Pass 1: Checking inodes, blocks, and sizes                    
Error reading block 34308186 (Attempt to read block from filesystem resulted in short read) while getting next inode from scan.  Ignore error? 

Answering yes will delete the inode, i.e. data will be lost. Answering no will leave the bad block in place and the problem will remain.

Non interactive

The -y option should not be placed after the -C option, as it would be understood as being an argument of the latter. Instead, put it in front.
I.e.
Wrong: e2fsck -vfFC0y /dev/sdc1
Right: e2fsck -yvfFC0 /dev/sdc1

Errors

Free blocks count wrong

# fsck -f /dev/sda2
fsck from util-linux 2.25.2
e2fsck 1.42.12 (29-Aug-2014)
/dev/sda2: recovering journal
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Free blocks count wrong (191550189, counted=192989110).
Fix?


Questions for which we are seeking answers:
- What can cause the above error?
- What to answer to the question "Fix?" What are the implications of answering yes or no?

External resources

http://en.wikipedia.org/wiki/E2fsprogs
http://en.wikipedia.org/wiki/Fsck
http://adminschoice.com/repairing-unix-file-system-fsck
http://lwn.net/Articles/248180/

e2fsck -vfFC0
complete check with maximum output.

Issues related to this page:

ProjectSummaryStatusPriorityCategoryLast updatedAssigned to
Linux softwareBest use of e2fsckactivecriticaltask7 years 17 weeks
Linux softwaree2fsck: non-desctructive, informative mode only?activenormalfeature request5 years 11 weeks
Linux softwareRunning e2fsck twice gives the same / differen…activenormalsupport request7 years 13 weeks
Linux software0 bad blocks ???activenormalsupport request7 years 13 weeks
Linux hardwarefsck: different scenarios for useactivenormaltask5 years 43 weeks
Linux hardwareWhat is a bad block?activenormaltask5 years 10 weeks