Centos7: Starting xinetd service with systemd

Question

I have a xinetd service from Centos6 and I want to port to Centos7 ie create a systemd service

# cat /etc/xinetd.d/br_rsh 
# default: on
# description: The rshd server is the server for the rcmd(3) routine and, \
#   consequently, for the rsh(1) program.  The server provides \
#   remote execution facilities with authentication based on \
#   privileged port numbers from trusted hosts.
service brshell
{
    port            = 591
    socket_type     = stream
    wait            = no
    user            = root
    log_on_success      += USERID
    log_on_failure      += USERID
    server          = /usr/sbin/in.br_rshd
    disable         = no
}

If i understood correctly, i need to break down the above file to two parts: one for brshell.socket and another for brshell.service. Then, I need to execute systemctl enable brshell.socket (what about brshell.service?)

What would these files look like and Where would these files go under?

Thank you

Answer 1

I'm assuming you already know about all the risks involved in running rshd, so I'll skip the "dire warnings" section of my talk. :-)

If your distribution includes the program that you're running, there's a strong chance that it already has the correct systemd files to migrate to (/usr/lib/systemd/system is where the distribution-supplied units files are located in CentOS IIRC. This is distro-specific; for example, I use Gentoo so they're located in /lib/systemd/system for me.)

If you need to make the unit files, it's pretty easy to migrate an xinetd service. You are correct in that you need both a socket and service file. By default, they both have the same base name; however, that's not a requirement, just a simplification. For your particular case, put the following into /etc/systemd/system (this is where you should put unit files that you create yourself):

brshell.socket

[Unit]
Description=rsh Server Socket

[Socket]
ListenStream=591
Accept=yes

[Install]
WantedBy=sockets.target

brshell.service

[Unit]
Description=rsh Server Daemon
After=network.target

[Service]
ExecStart=/usr/sbin/in.br_rshd

[Install]
WantedBy=multi-user.target

That's basically it! All you need to do next is run systemd enable brshell.socket (to have it start automatically at boot) and systemd start brshell.socket.