/usr/sbin/grub-mkconfig: 11: /etc/default/grub: : Permission denied

I ve a problem while updating my system.
I figured out that there is a problem by updating grub during the "sudo apt upgrade".

Removing linux-image-5.4.0-42-generic (5.4.0-42.46) ...
update-initramfs: Deleting /boot/initrd.img-5.4.0-42-generic
Sourcing file `/etc/default/grub'
/usr/sbin/grub-mkconfig: 11: /etc/default/grub: : Permission denied
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 127
dpkg: error processing package linux-image-5.4.0-42-generic (--remove):
 installed linux-image-5.4.0-42-generic package post-removal script subprocess returned error exit status 1
dpkg: too many errors, stopping
Errors were encountered while processing:
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)

than I tried also "sudo update-grub" and got this

Sourcing file `/etc/default/grub'
/usr/sbin/grub-mkconfig: 11: /etc/default/grub: : Permission denied

The grub file (/etc/default/grub) itself looks the following:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)

# Uncomment to disable graphical terminal (grub-pc only)

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
# Uncomment to disable generation of recovery mode menu entries

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

"ls -ldh /etc/default/grub"

-rw-r--r-- 1 root root 1,2K Nov 30 21:41 /etc/default/grub

Does anyone have an idea?

Asked By: EsShark


The error is the space in the assignment in


at line 11 of the /etc/default/grub file. It causes the shell (probably /bin/sh) to parse it as "assign nothing to GRUB_CMDLINE_LINUX and then run a command with no name with GRUB_CMDLINE_LINUX in its environment".

You can replicate the format of the error as follows:

$ sh -c 'GRUB_CMDLINE_LINUX= ""'
sh: 1: : Permission denied

whereas bash reports the somewhat more helpful

$ bash -c 'GRUB_CMDLINE_LINUX= ""'
bash: : command not found

The line should read


although GRUB_CMDLINE_LINUX= should work as well.

Answered By: EsShark
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