iPad Is the filesystem ever checked for errors before mounting volumes on iOS/iPadOS?

[brn823]

Hi there!

I own a 5th gen (2017) iPad currently running iPadOS 13.4. I would like to know if fsck is ever automatically run on the user Data volume to check for file system consistency errors, or if there is some other sanity check performed before mounting volumes, either during a normal device restart, a hard reset, or when choosing "Erase all content and settings", etc.

Today I looked at the Analytics logs (under Settings > Privacy) and noticed that my iPad encountered a kernel panic last year. Since the release of iPadOS, I have been frequently using my iPad for file operations, so I am a bit worried if the file system is in consistent state and about my data integrity. Looking at OTA system update log I see that fsck_apfs is executed only on the System volume during an update, so I was wondering how file system ensures data integrity for the user partition.

BTW Currently I am not experiencing any noticeable issues, like device restarts, system crashes, etc. I am more worried about the possibility of some silent corruption occuring on my device.

Thank you in advance!

 

[Lekro]

I’m also very interested in this, I’ve always wondered. I didn’t know about the integrity check on the system partition, thanks for that info.

Hopefully someone will know the answer.

 

[brn823]

I guess the easiest way to find out if the Data volume is ever checked is to take a look inside the fsck_logs file. However, fsck log is not available from the Analytics screen on iOS; as far as I know it can only be extracted using xcode on macOS, which I don't own So, if someone could share the contents of their iOS device's fsck_logs file I would be very grateful!

I attach an excerpt from the OTAUpdate log that can be seen through Analytics, which shows that the System volume is fsck'ed on system update. Unfortunately it seems that no similar check is performed at update time for Data volume.

EDIT: looking at the log again I noticed that fsck is executed on /dev/disk0s1, which I misread as /dev/disk0s1s1 (root volume). Which means that actually all volumes are checked when performing a system update Data volume is
/dev/disk0s1s2 /private/var apfs rw,nosuid,nodev 0 2
which is one of the volumes on disk0s1.
So saying that only System volume is checked on update was a mistake, I apologize for the confusion!

 

[Lekro]

According to this only the fsroot tree check is skipped on the Data partition.

 

[Lekro]

Nice. Does this mean if any corruption is present before the update, it is fixed after the update?

 

[brn823]

Nice. Does this mean if any corruption is present before the update, it is fixed after the update?

My best guess is that if there was any corruption on any of the volumes before the update is run, it would either be repaired by fsck during the update process, which should also leave a trace in logs, or the repair would fail along with the update, requiring recovery

 

[Lekro]

Good find.