ubuntu set boot command

overview

This document mainly records the method of setting the boot command Ubuntufor the system /etc/rc.local.

system version

Ubuntu 20.04

Set boot command

1. View rc-localservice status

sudo systemctl status rc-local

The output is as follows:

root@localhost:~$ systemctl status rc-local
● rc-local.service - /etc/rc.local Compatibility
     Loaded: loaded (/lib/systemd/system/rc-local.service; static; vendor preset: enabled)
    Drop-In: /usr/lib/systemd/system/rc-local.service.d
             └─debian.conf
     Active: inactive (dead)
       Docs: man:systemd-rc-local-generator(8)

2. Set rc-localthe service to start at boot

sudo systemctl enable rc-local

Note: Ubuntu 20.04 cannot directly enable rc-localthe service, an error will be reported, and rc-localthe service file needs to be created manually. The command error is as follows:

root@localhost:~$ sudo systemctl enable rc-local
[sudo] password for simple:
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled using systemctl.

Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
  .wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
  a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
  D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
  instance name specified.

3. Manually create system self-starting services

sudo vim /etc/systemd/system/rc-local.service

Enter the following:

[Unit]
 Description=/etc/rc.local Compatibility
 ConditionPathExists=/etc/rc.local
[Service]
 Type=forking
 ExecStart=/etc/rc.local start
 TimeoutSec=0
 StandardOutput=tty
 RemainAfterExit=yes
 SysVStartPriority=99
[Install]
 WantedBy=multi-user.target

4. Create rc.localthe file

sudo vim /etc/rc.local

Enter the following:

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
# Print the IP address
# _IP=$(hostname -I) || true
# if [ "$_IP" ]; then
#   printf "My IP address is %s\n" "$_IP"
# fi
exit 0

5. Set rc.localfile permissions

sudo chmod +x /etc/rc.local

6. Add boot command

Take deleting a redundant static route as an example. For example, there is a dual network card environment. One of the network cards needs to be used for intranet data transmission, and the other network card is used for accessing Internet data transmission. However, after the configuration is completed, it is found that The internal network data transmission is normal, but the Internet data transmission is abnormal. After investigation, it is found that the default gateway of the internal network card is set to the internal network gateway by mistake when configuring the internal network card, resulting in abnormal Internet data transmission. Therefore, this item needs to be deleted. Redundant static routes. The command to delete is sudo route del -net 0.0.0.0 dev enp0s8, and now I want to automatically execute this command when booting, so I need to add this command to rc.localthe file.

sudo vim /etc/rc.local

exit 0Add the following before

sudo route del -net 0.0.0.0 dev enp0s8

7. Enable rc-localservice

sudo systemctl start rc-local
sudo systemctl enable rc-local

8. View rc-localservice status

sudo systemctl status rc-local

9. Restart the system

sudo reboot

After the system restarts, you can check the routing table and find that the redundant static route has been deleted.