[Bug 1902103] Re: Ensure default fstab options are sane and consistent across all images

[Gauthier Jolly]

I will revert to the original description and move the SRU template to
LP1881006.

** Description changed:

- [Impact]
- 
-  * In cloud images, the ESP is currently mounted with default (0755)
-    permissions. This means anyone can read the ESP partition. This can
-    cause security issues as sensitive data might be put in this
-    partition[0]
- 
-  * The root filesystem partition uses defaults mount options. In case
-    of filesystem error, it is safer to use `remount-ro`. Also for cloud
-    usage (where storage can be expensive) it makes sense to mount the
-    root filesystem with `discard`. This will also align cloud images
-    fstab with what we have elsewhere.
- 
- [Test Plan]
- 
-  * Build an uefi image from the ubuntu-cpc project in livecd-rootfs
- 
-  * Launch in KVM
- 
-  * Check `/etc/fstab` content
- 
-  * Check that mount options are reflected in 'mount' command output
- 
-  * Ensure a non-root user can not access /boot/efi
- 
-  * Check 'lsblk -D' output to see that there is a non-zero discard block
- size for the root device (this check may be imperfect, the goal is to
- check that discard from fstab is enabled if available from the
- underlying block device)
- 
- [Where problems could occur]
- 
-  * Some users can have automation in place change those defaults. This
-    change might break their automation.
- 
-  * `error=remount-ro` might create issues for certain user. Especially if
-    the filesystem superblock default was set to `error=continue`. For
-    those users, any error that was previously ignored will make the
-    filesystem read-only.
- 
-  * `discard` parameter might have an impact on i/o throughput and reduce
-    read/write speed. Also some particular disk might have issues with
-    TRIM commands[1].
- 
- [original description]
  
  The default fstab entries for ubuntu cloud images are:
  
  LABEL=cloudimg-rootfs / ext4 defaults 0 0
  LABEL=UEFI /boot/efi vfat defaults 0 0
  
  These entries do not align with the defaults that we use elsewhere. We
  should decide on the defaults for fstab, and apply those consistently
  across all Ubuntu images.
  
  --
  
- quoted from ~xnox: I expect [these entries] to be:
+ quoted from ~xnox: the expect [these entries] to be:
  
  LABEL=cloudimg-rootfs / ext4 discard,errors=remount-ro 0 1
  LABEL=UEFI /boot/efi vfat umask=0077 0 1
- 
- [0] https://bugs.launchpad.net/cloud-images/+bug/1881006/comments/11
- [1] https://wiki.debian.org/SSDOptimization#WARNING

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https://bugs.launchpad.net/bugs/1902103

Title:
  Ensure default fstab options are sane and consistent across all images

Status in cloud-images:
  New
Status in curtin package in Ubuntu:
  Confirmed
Status in livecd-rootfs package in Ubuntu:
  Fix Released
Status in maas package in Ubuntu:
  Confirmed
Status in subiquity package in Ubuntu:
  Confirmed
Status in ubiquity package in Ubuntu:
  Confirmed

Bug description:

  The default fstab entries for ubuntu cloud images are:

  LABEL=cloudimg-rootfs / ext4 defaults 0 0
  LABEL=UEFI /boot/efi vfat defaults 0 0

  These entries do not align with the defaults that we use elsewhere. We
  should decide on the defaults for fstab, and apply those consistently
  across all Ubuntu images.

  --

  quoted from ~xnox: the expect [these entries] to be:

  LABEL=cloudimg-rootfs / ext4 discard,errors=remount-ro 0 1
  LABEL=UEFI /boot/efi vfat umask=0077 0 1

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