I've checked /etc/fstab and saw the following lines

<file system> <mount point>   <type>  <options>       <dump>  <pass>
 / was on /dev/sda1 during installation
UUID=some-hex-appears-here                /               ext4    errors=remount-ro 0       1
 /home was on /dev/sda5 during installation
UUID=another-hex-here                      /home           ext4    defaults        0       2

errors=remount-ro 0 1 concerns me because I would expect defaults instead of errors=remount-ro. Ubuntu runs as normal, but I have reasons to believe that Ubuntu might have being tempered with during the install process.

So what does this mean?

  • 1
    As a Ubuntu user downloaded from the official website, I can say that that is the default argument. – Lawful Lazy Oct 22 '16 at 23:13
up vote 9 down vote accepted

From the man page:

    Define the behavior  when  an  error  is  encountered.   (Either
    ignore  errors  and  just  mark  the  filesystem  erroneous  and
    continue, or remount the filesystem read-only, or panic and halt
    the  system.)   The default is set in the filesystem superblock,
    and can be changed using tune2fs(8).

Essentially, when there is an error mounting the disk with read/write privileges, it will instead mount it as 'read only'.

Whether or not 'defaults' are used in your setup are not necessarily relevant. Yes, you can expect 'defaults' here, but the lack therein doesn't hurt you a ton.

As well, the '0 1' part isn't part of the mount options - everything in an fstab line is space-delimited / tab-delimited - any space between things indicates the 'next argument' to use.

As a security person, though, my advice is that if you believe your system was tampered with during installation outside that of the typical installer, then you should not be using that system, and should install with a known, good ISO and no networking during that installation to rule out network boot installer images causing issues.

  • This is a low value test system that I am using to track the hardwire virus. Whenever infected keyoard and HDD are plugged in they yield a message "overclocking failed, press F2 for setup or F1 to load defaults". If you press those buttons computer stops working. If you don't and change the keyboard - you will be fine. – Alice Dec 8 '15 at 1:32
  • the *hardware virus. I am trying to find out what hardware is compromised and what hardware is ok. I have a collection of infected DVD-RWs, flash drives, keyboards, HDDs, etc. So I am trying to get an Idea if I should try to clean it or just dump those. A simple way would be to buy a new computer, which I will do once I know more about the behavior of this thing. Hence, I asked if these fstab settings are indicating infection or not. I will start a related topic once I gather some info. For now, I've changed the setting to "default" and the error check is gone. Thanks for your reply. – Alice Dec 8 '15 at 1:38
  • @Alice Hardware virus as in BadUSB? That is not fixable or avoidable you know.. – Thomas Ward Dec 8 '15 at 11:56
  • @ThomasWard Good answer. Just edited "fstab" to include my personal data partition with "defaults" options (which, for any reason, wasn't on the fstab list and couldn't be mounted ). – Jose Barakat Dec 13 '16 at 16:51

It means that if any errors occur when trying to mount the device, it will be remount as read-only.

The 0 and 1 on the last columns referring to and from fstab man pages:

The fifth field (fs_freq).

This field is used by dump(8) to determine which filesystems need to be dumped. Defaults to zero (don't dump) if not present.

The sixth field (fs_passno).

This field is used by fsck(8) to determine the order in which filesystem checks are done at boot time. The root filesystem should be specified with a fs_passno of 1. Other filesystems should have a fs_passno of 2. Filesystems within a drive will be checked sequentially, but filesystems on different drives will be checked at the same time to utilize parallelism available in the hardware. Defaults to zero (don't fsck) if not present.

  • 1
    True, but that was not the question. – PerlDuck Sep 1 at 8:21
  • 1
    I just wanted to add description for the remaining columns. – PsSc0rpi0n Sep 2 at 10:18

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