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Thread: Access to /boot/grub and /boot/efi

  1. #1
    Join Date
    Oct 2020
    Beans
    110

    Access to /boot/grub and /boot/efi

    Code:
    https://unix.stackexchange.com/questions/524622/what-is-the-relation-between-uefi-and-grub
    The above reference touches on relations between grub and efi.
    The relation between grub (file) and grub,cfg are known.

    The relation between system UEFI (firmware) and efi - starting with EFI partitions are somewhat
    foggy.

    My questions are:
    1. why /boot/grub contents is fully accessible and /boot/efi is not?
    2. What Linux security is in jeopardy , therefore "permission" to access is denied ?
    3. How do I bypass this "security" without screwing things up ?

    Note
    This is a single user , ME, system no community access is involved.


    Code:
    a@a-desktop://boot$ ls
    config-4.15.0-120-generic      memtest86+.elf
    config-4.15.0-122-generic      memtest86+_multiboot.bin
    efi                            System.map-4.15.0-120-generic
    grub                           System.map-4.15.0-122-generic
    initrd.img-4.15.0-120-generic  vmlinuz-4.15.0-120-generic
    initrd.img-4.15.0-122-generic  vmlinuz-4.15.0-122-generic
    memtest86+.bin
    a@a-desktop://boot$

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  2. #2
    Join Date
    Jun 2009
    Location
    SW Forida
    Beans
    Hidden!
    Distro
    Ubuntu

    Re: Access to /boot/grub and /boot/efi

    1 Secuity
    2. Windows formats like FAT32 & NTFS allows everyone to write into system. Mount of Windows type partitions is default for all files. Linux sets ownership & permission by file, so access can be limited and some script in a spreadsheet or word doc cannot modify it.
    3. So for improved security it is changed. I do change mine back to older setting to allow use, now, but may change again to 0077.

    14.04 fstab entry defaults allows access
    UUID=FD76-E33D /boot/efi vfat defaults 0 1
    16.04 & later fstab entry umask=0077 totally restricts access
    UUID=68CD-3368 /boot/efi vfat umask=0077 0 1

    I found the standard remount after editing fstab, does not immediately give access.
    I have had to reboot.

    sudo nano /etc/fstab
    Also add noatime (SSD or flash drive)) or relatime(HDD)
    #Typical fstab entry:
    UUID=d65e4ad3-6315-4838-97a1-ec574cb8575f / ext4 noatime,errors=remount-ro 0 1
    #UUID=D966-440A /boot/efi vfat umask=0077 0 1
    UUID=D966-440A /boot/efi vfat defaults 0 1
    tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0
    # confirm entries work, if just return then ok
    sudo mount -a
    For more info on UEFI boot install & repair - Regularly Updated :
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

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