[arch-general] Mounting root according to fstab the first time (fstab in initrd)?

[Garmine 42]

(Yes, I use grub2.) Actually, grub-mkconfig is just a bunch of
scripts, I should be able to grep and cut fstab and generate rootflags
from that, shouldn't I? :)

Is the cmdline size still limited to 255 characters?

On 20 January 2016 at 21:48, Garmine 42 <mikro001 at gmail.com> wrote:
> I would like to avoid modifying rootflags inside grub config so if I
> change anything in fstab I don't have to change that in other places
> as well. Unless grub-mkconfig can somehow be taught to parse fstab and
> set the rootflags according to it.
>
> On 20 January 2016 at 21:43, Devon Smith <devo8604 at gmail.com> wrote:
>> Garmine,
>>     If you are using grub2 you should be able to add that option in
>> your grub config, then regenerate it, that will make that option
>> permanent and you wont have to add it every time at boot. Also, if
>> 'ro' is in your kernel params at boot, then im pretty sure masking the
>> remount service will ensure that your root remains mounted ro...
>>
>> Devon
>>
>> On Wed, Jan 20, 2016 at 1:34 PM, Garmine 42 <mikro001 at gmail.com> wrote:
>>> On 20 January 2016 at 21:18, Leonid Isaev
>>> <leonid.isaev at jila.colorado.edu> wrote:
>>>> On Wed, Jan 20, 2016 at 09:01:22PM +0100, Garmine 42 wrote:
>>>>> There was a discussion on the linux-btrfs mailing list about this, and
>>>>> for example the btrfs space_cache option can not be changed with a
>>>>> remount - this causes the fstab file's space_cache option to be
>>>>> basically ignored. I want to eliminate this kind of issue on my setup,
>>>>> that's why I need to avoid root being remounted. Instead I want root
>>>>> to be mounted with the options specified in fstab the first (and only)
>>>>> time.
>>>>
>>>> Why is it ignored?
>>>> /dev/sda4 on / type btrfs (ro,nodev,relatime,compress=zlib,ssd,space_cache,autodefrag,subvolid=257,subvol=/_root)
>>>>                                                                ^^^^^^^^^^^
>>>
>>> The linux-btrfs discussion suggests that some mount options might be
>>> unchanged after a remount even if it should change based on the fstab.
>>>
>>> Although that particular discussion's exact problem was something else
>>> in my opinion, so they might be wrong on that. The fix for that
>>> problem was including the problematic option (space_cache=v2) in the
>>> rootflags parameter. Considering the cmdline size is limited and I
>>> want to avoid modifying that all the time, I want to mount the root
>>> volume with the correct flags in the first place.
>>>
>>>> Also, there is fstab in the initramfs:
>>>> $ lsinitcpio /boot/initramfs-linux.img | grep fstab
>>>> etc/fstab
>>>
>>> That fstab is an empty file (ran in an uncompreseed initrd):
>>> % wc -c etc/fstab
>>> 0 etc/fstab
>>>
>>>> Have you tried masking the systemd-remount-fs.service?
>>>
>>> First I will try to exclude root= and rootflags= parameters from the
>>> cmdline and include the fstab via mkinitcpio and see if it finds the
>>> root. Do I want to mask remount-fs in this case?
>>>
>>>> Cheers,
>>>> --
>>>> Leonid Isaev
>>>> GPG fingerprints: DA92 034D B4A8 EC51 7EA6  20DF 9291 EE8A 043C B8C4
>>>>                   C0DF 20D0 C075 C3F1 E1BE  775A A7AE F6CB 164B 5A6D