How can we resume the script from where it left off after resume in Linux Ubuntu? Is anyway we can make use of rc.local?

Question

How the rc.local can be used to resume the script after resume?

Some explanation from user's comment:

Boot_desired_kernel() {} 
# after this system will reboot 
Do_task(){} 
Do_task() /*

Using the pasting the file in init.d and updating it is working for script to run after reboot but what I am expecting is the script should start where it left off before reboot

Answer 1

I don't know, how to do it using rc.local, but maybe you will be satisfied with systemd way:

• Create the new systemd service:

  sudo vim.tiny /etc/systemd/system/startscript.service
  

  You could nano instead of vim.tiny or other editor you like
  Paste the next to it:

  [Unit]
  Description=Start script after resume
  After=suspend.target
  
  [Service]
  Type=simple
  ExecStart=/full/path/to/the/script.sh
  
  [Install]
  WantedBy=suspend.target
  

• Enable and start the service:

  sudo systemctl enable startscript && sudo systemctl start startscript
  

Answer 2

I don't know how to resume script execution after reboot, but you could check kernel version and if the kernel version is what you need, you could execute the rest of the script skipping the kernel changing and rebooting part as in the next script. But the script will be executed before the first reboot and after each reboot.

#!/bin/bash

kernel="5.3.0-40-generic"

if [[ $(uname -a) != *$kernel* ]]; then
    kernlist="$(grep -i "menuentry '" /boot/grub/grub.cfg|sed -r "s|--class .*$||g")"
    printf "%s$kernlist\n" | logger
    menuline="$(printf "%s$kernlist\n"|grep -ne $kernel | grep -v recovery | cut -f1 -d":")"
    menunum="$(($menuline-2))"
    grub-reboot "1>$menunum"
    echo "The next grub's menu entry will be choosen after the reboot:\n 1>$menunum" | logger
    reboot
fi

if [[ $(uname -a) == *$kernel* ]];
  then echo "This command is executed after reboot to $kernel" | logger;
fi

echo "Currently running kernel version is: $(uname -r)" | logger

After reboot it skips running kernel selecting part if the current kernel is of required version and echoes "This command is executed after reboot to KERNEL_VERSION_HERE" if you run journalctl -b | grep This or:

$ journalctl -b | grep Currently
Apr 13 17:35:51 lenovo root[1013]: Currently running kernel version is: 5.3.0-40-generic

After adding this to systemd it loads with default kernel and then automatically reboots and boots with 5.3.0-40-generic kernel.

$ cat /etc/systemd/system/resscript.service 
[Unit]
Description=Start script after reboot
After=network.target

[Service]
Type=simple
ExecStart=/home/user/test/resscript.sh

[Install]
WantedBy=multi-user.target