# Can crash be caused by read only root partition?



## Marcin Solski (Apr 7, 2016)

Hello All.

This is my first post here. I'm using FreeBSD for quite a long time but I'm still amateur. Currently I'm using it on a home machine to handle NFS mainly.

Yesterday I have installed 10.3-R. Configured all as usual with minimal kernel (removed unnecessary drivers, debugging, tracing and INET6). After all config has been completed I set root partition as read only (var, tmp, home are read-write on separate partitions).

After a day I was trying to remount / rw with command 'mount -u -w /' but it failed. System accepted command but it did not cause any effect (mount was still showing / as ro). After three tries system crashed suddenly. No panic, no logs, no dump. Hard, immediate restart. As this issue is hard to replicate I didn't try to run generic kernel. No compiler flags were used during kernel build and usb, sound and nic are loaded as modules.

Before it I was using 10.2-R with the very same kernel config file (same hardware, too) and i didn't experience it for more than half year. 

Please share what in your opinion could be the problem here. How to troubleshoot?


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## Terry_Kennedy (Apr 7, 2016)

Marcin Solski said:


> Please share what in your opinion could be the problem here. How to troubleshoot?


The only thing that comes to mind is that reroot support was added to 10.3:


			
				10.3 Release Notes said:
			
		

> •The initial implementation of reroot support has has been added to the reboot(8) utility, allowing the root file system to be mounted from a temporary source file system without requiring a full system reboot.


It might be some interaction with that code. I'd suggest asking on freebsd-stable@ as you're more likely to catch the attention of a developer there.


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