systemctl start service does not work in SPEC file

I met a problem that the command "sudo systemctl start xxx.service" in my SPEC file does not work when upgrading my RPM package, following is my %post script in SPEC file,

%post
echo "---------------------------- post $1 -------------------------------"
# refresh installation
if [ $1 == 1 ]; then
  sudo echo "Installation finished."
# upgrade installation
elif [ $1 -gt 1 ]; then
  sudo echo "Starting service xxx.service..."
  sudo /usr/bin/systemctl enable xxx.service > /dev/null 2>&1
  sudo /usr/bin/systemctl start xxx.service
  sleep 10
  sudo echo "Finished."
fi
exit 0

I'm sure that the service file already exists in directory /usr/lib/systemd/system, and I can start it manually using the command "sudo systemctl start xxx.service".

And I found that the "sleep 10" command does not work too.

Very appreciated if there is any suggestion about this issue, thanks.

Solution

Few issues:

You're not supposed to use sudo in scriplets, because 1) it may not be installed 2) rpm installation runs as superuser anyway
You should use the standard RPM macros for SystemD as opposed to reinventing the wheel.

Essentially that simply goes down to:

%{?systemd_requires}
BuildRequires: systemd

# ...

%post
%systemd_post %{name}.service

%preun
%systemd_preun %{name}.service

%postun
%systemd_postun_with_restart %{name}.service

# ...

Take note that the SystemD macros for CentOS/RHEL are within systemd package, while in Fedora they are now in systemd-rpm-macros.