Similar to this post, the file system on my home partition suddenly became read only. On reboot, my HHD containing this partition would not mount and I had to use fsck to repair it. Now it works fine. I don't recall doing anything particular that day and I was wondering: what can cause this kind of unexpected corruption?
My computer is setup only with one OS: Xubuntu 16.04 and I have an SSD for the OS and an HHD for my home. Note that I am not trying to have an answer specific to my issue. I only want to understand better what are those types of corruption and where they usually come from.
Generally, if there are any issues with I/O, the system will mount as read-only so that further writes don’t damage the file system, but you can attempt to salvage whatever you can before attempting a check/repair (fsck).
I would also have a look at the device’s SMART stats using the Disks utility to see if it is failing. Reallocated sectors and read/write/seek error rates may point to a failing device. But I’ve also had cases where the drives were fine and the motherboard was causing erratic behavior to devices connected to a specific set of SATA ports. Many variables to consider…
Source: Filesystem suddenly read-only? | Unix & Linux Stack Exchange