Add support for systemd's systemctl reboot for passwordless reboots

[matkeith]

I want to suggest some general feature

Topgrade should allow for reboot without requiring a sudo password by using command "systemctl reboot" if the system is running systemd.

More information

If the linux system uses systemd you do not need to reboot using sudo, which requires typing in a password. Instead use the command "systemctl reboot" which will just reboot the system without further user action

https://www.freedesktop.org/software/systemd/man/latest/sd_booted.html
"Internally, this function checks whether the directory /run/systemd/system/ exists. A simple check like this can also be implemented trivially in shell or any other language."

Seems like you can check for this folder in rust and then execute the alternate command "systemctl reboot" instead in the below function

pub fn reboot() -> Result<()> { print!("Rebooting..."); Command::new("sudo").arg("reboot").status_checked() }

I do not know how to test this from a side branch, as I am using bazzite, an immutable desktop. I'm willing to give it a try though if there are instructions somewhere.

[SteveLauC]

Thanks for the report!

Does the reboot command on your Linux box need sudo, from this answer, reboot since Ubuntu 16 does not need sudo, and I started using Fedora since 36, I don't remember sudo is ever needed. Are they due to the switch to the systemd init program?

Though the reboot on my macOS machine does need sudo.

[matkeith]

@SteveLauC yeah it looks like typing "reboot" without sudo works as well for me on bazzite as well

[SteveLauC]

I found that this root-less reboot only works if you have local access to your machine, i.e., not ssh, when you do it via ssh:

$ reboot
Call to Reboot failed: Interactive authentication required.

See also: Getting errors whenever I try to reboot or shutdown through terminal

[matkeith]

Bummer. I found some additional info from ubuntu's forum as well
https://askubuntu.com/questions/1005884/sudo-reboot-vs-reboot-what-is-the-difference

specifically these criteria:

On Ubuntu 14.10 and older, sudo is required.

The introduction of Systemd in 15.04 changed the way Ubuntu handles shutdown and reboot:

When a single user is logged in, sudo isn't necessary. When more than one user is logged in then sudo is required.

Applications can inhibit shutdown and reboot. You override these inhibitions with sudo.

A single user logged in via ssh still requires sudo.

so it seems there are more nuances involved than simply using ssh. reboot would fail on a multiuser system or if an application were to prevent it.

matkeith@mattlaptop:~$ ls -al $(which reboot)
lrwxrwxrwx. 19 root root 16 Jul  5 15:30 /usr/sbin/reboot -> ../bin/systemctl

reboot is just pointed at systemctl reboot anyhow. I don't see a way around this intelligently. oh well =/

[SteveLauC]

So, it seems that:

• If we are running Topgrade through SSH, then sudo is needed
• Otherwise, check if there are more than one user is logged in, if so, sudo is also needed.

Let me implement this.