CentOS

I have just performed a fresh install of CentOS 6.9.
Everything went well, but the files on a mounted 1T external disk become readonly very easily and suddenly.

Could it be due to the fact that /
is left with 184M?

I am going to use gparted to increase the size and see if the problem goes away.

Much more likely that you're getting an i/o error on the drive and the whole thing is set r/o. Check your logs for errors.

run the command: and see what's there. As Trevor suggested, most likely, you will see an indication that the whole filesystem is readonly.

Before I read the two replies, I have increased / to 50GB to minimize weird behavior.

If / size is not a problem then I can't think of a good reason why this thing happen.

This external 1TB disk is being used almost everyday on two other CentOS machines 6.6 or 6..1 and these two
do not have this problem at all (as far as I can remember).

Usually when there is an I/O error, there will be I/O error on the
prompt line (or screeen) indicating bad things have happened. ( I use rsync a lot and I have seen this)
In this case, the error is obvious and I know what to do (reformat the disk or retire the faulty disk)

The recent readonly problem happens a few times as I was editing a file on the mounted disk when I am setting up things
in the new CentOS 6.9.

If / size is not an issue, then the best guess I have right now is that the external hard drive goes to sleep due to inactivity (no reading or saving) and
somehow the power saving kicks in that confuses the OS thinking that the disk is unstable? Or the USB slot is problematic?

Anyway, I will report back when there is a new thing.

Just this moment I have copied some 200 GB files from the external disk to a internal disk of
the computer successfully.

Just to report back. readonly seems to go away after I increased the size of / to 50 GB. Also I place the magnetic hard drive away from
a bunch of wires that comes with the AC adapter (who knows if the strayed magnetic fields are playing some tricks here).

Just to report back again:

I have plugged in a USB port that made the mounted file system readonly very soon. Observed on CentOS 6.9 and CentOS 7.
This is a new computer, I notice the port has a label called SS (SuperSpeed). Not sure if that is the reason.
Do I need to test other SS USB ports. I have to be very systematic in my testing if needed.

Is the stability of the SS USB port well tested on CentOS 6.9 or Centos 7.3?

Right now I am using a port (at the back of computer) that is not labelled SS. I used it yesterday and I did not see any instability (
ie., I cannot write the disk since it is readony).

I believe USB SS is the same as USB 3.0.
Do you know which USB 3.0 chipset your motherboard uses?

I googled about SS and it seems USB 3.0. I have 4 ports that are not labeled under SS. I use one of them right now and never have I had any issue.

Anyway, since I am on this topic, I do not understand booting messages:

usb-4-4: device not acceptinng address 3, error -62
usb 3-0:1.0: unable to enumerate USB device on port 4

Reason is that the usb support is not up-to-date on CentOS 6.9?