Why systemd-analyze from systemd service at multi-user.target does not output anything

manpreet Best Answer 2 years ago

Having the following script: boot-time-log.sh

#!/usr/bin/env bash

BOOT_TIME=$(systemd-analyze | cut --fields=10 --delimiter=\ )
echo -e "Boot time: $BOOT_TIME\n" > /var/log/boot_time.txt

And the following systemd service (enabled): log_at_boot.service

[Unit]
Description=Log boot time 
User=root
Group=root

[Service]
ExecStart=/usr/bin/boot-time-log.sh

[Install]
Wants=network-online.target
After=network-online.target
Wants=multi-user.target
After=multi-user.target

When I restart the PC the contents of /var/log/boot_time.txt are:

Boot time: 

And if I run the script manually, then the contents are:

Boot time: 29.382s

How can I get the service execution to have the same output than the manual execution?