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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?

  • 1
    hardware. Most likely a bad drive or faulty cable. – jordanm Dec 16 '16 at 20:03
  • Could have been the filesystem got mounted read-only. – DopeGhoti Dec 16 '16 at 20:59
  • @DopeGhoti It might, but that would have been a consequence of the same I/O problem, not a cause of these messages. – Gilles Dec 18 '16 at 22:32
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Next step would probably involve looking at your dmesg | tail -40 output. Then again, it would probably answer with an other Input/output error. I guess you had to physically reboot this machine/commands were failing as well?

Looks like your root filesystem is gone. Could be a problem with a disk, some sata cable, or a faulty RAID array.

  • Yes, I had to physically reboot. So, you eliminate security risk? Or I can focus on something to be more sure? – xralf Dec 16 '16 at 19:56
  • By focus, I mean, use the command with grep, to get more precise information related to the situation before reboot. – xralf Dec 16 '16 at 20:00
  • From my experiences, these kind of messages are related to some hardware issue. You could try configuring rsyslog to forward messages to some remote logger: missing disks/broken root doesn't mean your running processes are necessarily broken too. – SYN Dec 16 '16 at 20:03
  • If file input/output errors, my bet is grep won't work any better. – SYN Dec 16 '16 at 20:03
  • dmesg shouldn't fail with an input/output error because dmesg info is stored in memory, not on disk. – jordanm Dec 16 '16 at 20:04

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