[systemd-devel] Multiple services using the same core service?

[林自均]

Hi folks,

I am trying to achieve:

    # systemctl start sshd-shell.service (1)
    # systemctl start sshd-sftp.service (2)
    # systemctl stop sshd-shell.service (3)
    # systemctl stop sshd-sftp.service (4)

Before the command (1), sshd is not running. By typing (1),
/etc/sshd_config is configured to accept ssh shell connections but no sftp
connections, and then start sshd. By typing (2), /etc/sshd_config is
configured to accept sftp connections too, and sshd is reloaded. By typing
(3), /etc/sshd_config is configured to refuse ssh shell connection, and
sshd is reloaded again. By typing (4), sshd will be stopped.

Basically, I wrote the following 3 service units:

- sshd-core.service: the original sshd
- sshd-shell.service: ssh shell
- sshd-sftp.service: sftp server

The units looks like:

    # sshd-core.service
    [Unit]
    Description=OpenSSH Daemon
    After=network.target
    StopWhenUnneeded=yes
    RefuseManualStart=yes

    [Service]
    ExecStart=/usr/bin/sshd -D
    ExecReload=/bin/kill -HUP $MAINPID
    KillMode=process
    Restart=always

    # sshd-shell.service
    [Unit]
    Requires=sshd-core.service
    After=sshd-core.service
    PropagatesReloadTo=sshd-core.service

    [Service]
    Type=oneshot
    ExecStart=/usr/local/bin/config-sshd.sh enable-shell
    ExecStop=/usr/local/bin/config-sshd.sh disable-shell
    ExecReload=/bin/true
    RemainAfterExit=yes
    ExecStartPost=/bin/sleep 1
    ExecStartPost=-/bin/systemctl reload --no-block sshd-core.service
    ExecStopPost=-/bin/systemctl reload --no-block sshd-core.service

And sshd-sftp.service is similar to sshd-shell.service except the
ExecStart= and ExecStop= configures sftp.

The current problem is that I don't know if there is a better way to
achieve this. For example, I have to sleep 1 second before reloading
sshd-core.service in sshd-shell.service because otherwise sshd didn't setup
the signal handler for SIGHUP and will terminate itself. Or systemd doesn't
suggest such use case?

Thanks for any comments.

John
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