At certain time, various commands started to give various error messages.
I catched a few of them and then rebooted the system and these commands were working.
$ mkdir x mkdir: cannot create directory `x': $ file x.txt bash: /usr/bin/file: Input/output error $ touch x.txt Segmentation fault
There were other commands giving the same error messages. ls, px was working. Some command output "read/only filesystem".
Now it's OK after reboot.
What could I try (to measure or diagnose) to know more about what was happening? If it's rather relating to hardware or security?