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1,821
Votes: 2
✅ Solution
Tags:
boot
grub2
bash
cron
Link:
🔍 See Original Answer on Ask Ubuntu ⧉ 🔗
URL:
https://askubuntu.com/q/885030
Title:
How to cycle through grub background images every boot
ID:
/2017/02/19/How-to-cycle-through-grub-background-images-every-boot
Created:
February 19, 2017
Edited: June 12, 2020
Upload:
September 15, 2024
Layout: post
TOC:
false
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Copy to clipboard: false
Short Answer
#!/bin/bash
CURR_FILE=$(cat /etc/default/grub | grep BACKGROUND) # Get grub current line
CURR_FILE=$(cut -d "=" -f 2 <<< "$CURR_FILE") # File name only
CURR_FILE=$(echo "$CURR_FILE" | tr -d '"') # Remove double quotes
for ALL_FILES in /home/rick/Pictures/Wallpaper/640x480*; do # Loop through every file
if [[ "$FIRST_FILE" == "" ]]; then
FIRST_FILE="$ALL_FILES"
elif [[ "$MATCH_FILE" != "" ]]; then
NEXT_FILE="$ALL_FILES"
break # We've got it!
fi
if [[ "$CURR_FILE" == "$ALL_FILES" ]]; then
MATCH_FILE="$ALL_FILES" # We found our current file entry
fi
done
# If $NEXT_FILE empty we hit end of list so use First file name
if [[ "$NEXT_FILE" == "" ]]; then
NEXT_FILE="$FIRST_FILE"
fi
# replace background file name in grub source file
sed -i "s|$CURR_FILE|$NEXT_FILE|g" /etc/default/grub
# replace background file name in grub configuration file
# Backup... just in case :)
cp /boot/grub/grub.cfg /boot/grub/grub.cfg~
# Short cut so we don't have to run `sudo update-grub`
sed -i "s|$CURR_FILE|$NEXT_FILE|g" /boot/grub/grub.cfg
Credits
After much googling this morning along with trial and error the problem was 90% solved. Then with incredible assistance in chat room from Pilot6, Terdon and Zanna the hardest part for me (using sed) was solved.
Considerate comments were also posted by cl-netbox and Byte Commander making Ask Ubuntu’s chat room the friendliest most homogeneous technical chat room I’ve frequented in my two decades on the net.
Call script every boot with cron
Create the file /etc/cron.d/cycle-grub-background containing:
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
@reboot root /usr/local/bin/cron-reboot-cycle-grub-background
NOTE: create file using sudo powers. No need to mark it as executable but doing so won’t hurt either.
Long Answer with debug and variable declarations
#!/bin/bash
# NAME: cron-reboot-cycle-grub-background
# DATE: February 18, 2017. Modified April 9, 2017.
# PATH: /usr/local/bin/
# DESC: Cycle through available wallpaper for grub background
CURR_FILE=$(cat /etc/default/grub | grep BACKGROUND) # Get grub current line
echo "Grub line: $CURR_FILE"
CURR_FILE=$(cut -d "=" -f 2 <<< "$CURR_FILE") # File name only
CURR_FILE=$(echo "$CURR_FILE" | tr -d '"') # Remove double quotes
echo "Current file: $CURR_FILE"
FIRST_FILE=""
NEXT_FILE=""
MATCH_FILE=""
for ALL_FILES in /home/rick/Pictures/1600x900/*; do # Loop through every file
if [[ "$FIRST_FILE" == "" ]]; then
FIRST_FILE="$ALL_FILES"
fi
if [[ "$MATCH_FILE" != "" ]]; then
NEXT_FILE="$ALL_FILES"
break # We've got it!
fi
if [[ "$CURR_FILE" == "$ALL_FILES" ]]; then
MATCH_FILE="$ALL_FILES" # We found our current file entry
fi
done
# If $NEXT_FILE empty we hit end of list so use First file name
if [[ "$NEXT_FILE" == "" ]]; then
NEXT_FILE="$FIRST_FILE"
fi
echo "First file: $FIRST_FILE"
echo "Match file: $MATCH_FILE"
echo "Next file: $NEXT_FILE"
# replace background file name in grub source file
sed -i "s|$CURR_FILE|$NEXT_FILE|g" /etc/default/grub
# replace background file name in grub control file
# Backup... just in case :)
cp /boot/grub/grub.cfg /boot/grub/grub.cfg~
# Short cut so we don't have to run `sudo update-grub`
sed -i "s|$CURR_FILE|$NEXT_FILE|g" /boot/grub/grub.cfg
# Now next reboot will have new background image
exit 0
A few notes
The long version answer uses a different picture directory name than the short version. In either case you need to update to whatever directory your images are stored in.
sed usually uses / as a delimiter however our path/file names contain / so we use | instead.
The conventional method after changing /etc/default/grub is to run sudo update-grub. However this takes 12 seconds on my machine the machine could be rebooted while this lengthy process was being run. Given that systemd-inhibit would have to be used.
The short cut uses sed to search and replace within /boot/grub/grub.cfg. A backup of the file is made just in case something goes wrong. The way cron reboot is setup on this machine however the process is completed by the time the login password is typed and a terminal window is opened to check on the update.