Fstab mounts root as read only, what could be the problem?

Question

linux

Good afternoon!
In general, I have such a problem - ubuntu mounts the root in read only.
The pc has a kingstone ssd 120gb divided into 5 partitions. And seagate 1tb divided into 3 sections.
Kingstone - sdb
sdb1 - win10 boot partition
sdb2 - win10 itself
sdb3 - /boot
sdb4 - /
sdb5 - swap
Seagate sda
​​sda1 ntfs
sda2 /var
sda3 /home
When booting with fstab
/dev/sdb4 / discard,errors=remount-ro 0 1
sdb4 is mounted to the root but only in read only
Replacing discard,errors=remount-ro with defaults solves the problem.
The standard ubuntu disk check utility says that the disk is in order fsck does not solve the problem either.
Who faced similar tell in which direction to dig to solve this problem?
If it weren’t for the update to 16.04, I wouldn’t have remembered about it, but it still started on 15.04, so the version doesn’t play a role here. ssd after that has been working for more than six months without problems.

Answer 1

> When booting with the rule fstab
> /dev/sdb4 / discard,errors=remount-ro 0 1
> sdb4 is mounted to the root but only in read only
> Replacing discard,errors=remount-ro with defaults solves the problem.
Did you try to check? In your line it is said IN ERRORS TO MOUNT IN RO. And with this line it is mounted in ro. What could be the matter? Here is a riddle!
> If not for the update to 16.10
, return the time machine to its place! 16.10 will be released only in six months.

Answer 2

Try removing the "discard" parameter. It is deprecated and slows down the removal, it is recommended to just do "fstrim --all" once a week.
Well, it would be nice to look in dmesg to see how the mount is going.