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Suppose that I want my server to sleep on any HTTP request to the path /sleep (i.e. http://hostname/sleep), but also send a complete response (HTTP 200) before sleeping.

Using nginx with FastCGI, I have configured the path in the nginx configuration:

location /sleep {
    fastcgi_pass unix:/path/to/fcgiwrap.socket;
    include fastcgi_params;
    fastcgi_param SCRIPT_FILENAME /path/to/script.sh;
}

This invokes the following script (/path/to/script.sh):

#!/bin/sh
# -*- coding: utf-8 -*-
cat << EOF
Content-Type: text/html

<html><head><title>Sleep</title><meta charset="UTF-8"></head>
<body><p>Sleep: $(date)</p></body></html>
EOF
sleep 1 && sudo systemctl suspend < /dev/null > /dev/null 2>&1 &

Even though this will sleep the system, FastCGI will block until the child process completes, meaning that the web request will not complete before the system sleeps. So, how do I detach that final command from oversight by FastCGI so that the response completes, yet the command continues in the background, in this case ultimately to sleep the system?

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  • It shouldn't matter whether I use nginx or Apache, so I am not looking for an nginx-specific solution like setting the request timeout shorter than the script wait time (i.e. sleep 5 in the script, but kill the request after 2 seconds). Commented Jun 5, 2021 at 5:54

2 Answers 2

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You could decouple the cgi and the suspend by interposing a file used as a systemd trigger. See man systemd.path for this path-based activation of a unit. It has the advantage of not needing to use sudo from the cgi.

Create a unit file /etc/systemd/system/mycgitrigger.path

[Path]
PathModified=/some/writeable/file
[Install]
WantedBy=multi-user.target

and enable it. Change the cgi script to simply write anything into the file /some/writeable/file in order to trigger the shutdown. Put the short timeout and shutdown command in a unit file /etc/systemd/system/mycgitrigger.service (which does not need to be enabled).

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  • 1
    For people who have familiarity with Systemd, they probably don't need the obvious tip that to have this work immediately, before the next boot, you must start the .path Unit explicitly (systemctl start mycgitrigger.path). Commented Jun 8, 2021 at 0:19
0

The obvious solution would be

echo "sleep 1 && sudo systemctl suspend" | at now
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