Update podman-generate-systemd man page

Update links, content, and adding more examples to show how to run
the generated .service files as root and non-root. Fix for #5497

Signed-off-by: Sujil02 <sushah@redhat.com>

1 files changed, 118 insertions, 5 deletions

diff --git a/docs/source/markdown/podman-generate-systemd.1.md b/docs/source/markdown/podman-generate-systemd.1.md
index 81db0bd54..fa04f81f9 100644
--- a/docs/source/markdown/podman-generate-systemd.1.md
+++ b/docs/source/markdown/podman-generate-systemd.1.md
@@ -1,7 +1,7 @@
 % podman-generate-systemd(1)
 
 ## NAME
-podman\-generate\-systemd - Generate systemd unit file(s) for a container. Not supported for the remote client
+podman\-generate\-systemd - Generate systemd unit file(s) for a container or pod. Not supported for the remote client
 
 ## SYNOPSIS
 **podman generate systemd** [*options*] *container|pod*
@@ -27,7 +27,9 @@ Use the name of the container for the start, stop, and description in the unit f
 **--new**
 
 Create a new container via podman-run instead of starting an existing one.  This option relies on container configuration files, which may not map directly to podman CLI flags; please review the generated output carefully before placing in production.
-Since we use systemd `Type=forking` service, using this option will force the container run with the detached param `-d`
+Since we use systemd `Type=forking` service, using this option will force the container run with the detached param `-d`.
+
+Note: Generating systemd unit files with `--new` flag is not yet supported for pods.
 
 **--time**, **-t**=*value*
 
@@ -40,7 +42,10 @@ Set the systemd restart policy.  The restart-policy must be one of: "no", "on-su
 
 ## Examples
 
-Create and print a systemd unit file for a container running nginx with an *always* restart policy and 1-second timeout to stdout.
+### Generate and print a systemd unit file for a container
+
+Generate a systemd unit file for a container running nginx with an *always* restart policy and 1-second timeout to stdout.
+
 ```
 $ podman create --name nginx nginx:latest
 $ podman generate systemd --restart-policy=always -t 1 nginx
@@ -64,7 +69,42 @@ PIDFile=/run/user/1000/overlay-containers/de1e3223b1b888bc02d0962dd6cb5855eb0073
 WantedBy=multi-user.target default.target
 ```
 
-Create systemd unit files for a pod with two simple alpine containers. Note that these container services cannot be started or stopped individually via `systemctl`; they are managed by the pod service. You can still use `systemctl status` or journalctl to examine them.
+### Generate systemd unit file for a container with `--new` flag
+
+ The `--new` flag generates systemd unit files that create and remove containers at service start and stop commands (see ExecStartPre and ExecStopPost service actions). Such unit files are not tied to a single machine and can easily be shared and used on other machines.
+
+```
+$ sudo podman generate systemd --new --files --name bb310a0780ae
+# container-busy_moser.service
+# autogenerated by Podman 1.8.3
+# Fri Apr  3 09:40:47 EDT 2020
+
+[Unit]
+Description=Podman container-busy_moser.service
+Documentation=man:podman-generate-systemd(1)
+Wants=network.target
+After=network-online.target
+
+[Service]
+Environment=PODMAN_SYSTEMD_UNIT=%n
+Restart=on-failure
+ExecStartPre=/usr/bin/rm -f %t/%n-pid %t/%n-cid
+ExecStart=/usr/local/bin/podman run --conmon-pidfile %t/%n-pid --cidfile %t/%n-cid --cgroups=no-conmon -d -dit alpine
+ExecStop=/usr/local/bin/podman stop --ignore --cidfile %t/%n-cid -t 10
+ExecStopPost=/usr/local/bin/podman rm --ignore -f --cidfile %t/%n-cid
+PIDFile=%t/%n-pid
+KillMode=none
+Type=forking
+
+[Install]
+WantedBy=multi-user.target default.target
+```
+
+### Generate systemd unit files for a pod with two simple alpine containers
+
+Note `systemctl` should only be used on the pod unit and one should not start or stop containers individually via `systemctl`, as they are managed by the pod service along with the internal infra-container.
+
+You can still use `systemctl status` or `journalctl` to examine container or pod unit files.
 ```
 $ podman pod create --name systemd-pod
 $ podman create --pod systemd-pod alpine top
@@ -96,9 +136,82 @@ PIDFile=/run/user/1000/overlay-containers/ccfd5c71a088768774ca7bd05888d55cc28769
 WantedBy=multi-user.target default.target
 ```
 
+### Installation of generated systemd unit files.
+
+Podman-generated unit files include an `[Install]` section, which carries installation information for the unit. It is used by the enable and disable commands of systemctl(1) during installation.
+
+Once you have generated the systemd unit file, you can copy the generated systemd file to ```/usr/lib/systemd/system``` for installing as a root user and to ```$HOME/.config/systemd/user ``` for installing it as a non-root user. Enable the copied unit file or files using `systemctl enable`.
+
+Note: Coping unit files to ```/usr/lib/systemd/system``` and enabling it marks the unit file to be automatically started at boot. And smillarly, coping a unit file to ```$HOME/.config/systemd/user ``` and enabling it marks the unit file to be automatically started on user login.
+
+
+```
+# Generated systemd files.
+$ podman pod create --name systemd-pod
+$ podman create --pod systemd-pod alpine top
+$ podman generate systemd --files --name systemd-pod
+
+# Copy all the generated files.
+
+$ sudo cp pod-systemd-pod.service container-great_payne.service /usr/lib/systemd/system
+$ systemctl enable pod-systemd-po.service
+Created symlink /etc/systemd/system/multi-user.target.wants/pod-systemd-po.service → /usr/lib/systemd/system/pod-systemd-po.service.
+Created symlink /etc/systemd/system/default.target.wants/pod-systemd-po.service → /usr/lib/systemd/system/pod-systemd-po.service.
+$ systemctl is-enabled pod-systemd-po.service
+enabled
+```
+To run the user services placed in `$HOME/.config/systemd/user/` on first login of that user, enable the service with --user flag.
+
+```
+$ systemctl --user enable <.service>
+```
+The systemd user instance is killed after the last session for the user is closed. The systemd user instance can be kept running ever after the user logs out by enabling `lingering` using
+
+```
+$ loginctl enable-linger <username>
+```
+### Use `systemctl` to perform operations on generated installed unit files.
+
+Create and enable systemd unit files for a pod using the above examples as reference and use `systemctl` to perform operations.
+
+Since systemctl defaults to using the root user, all the changes using the systemctl can be seen by appending sudo to the podman cli commands. To perform `systemctl` actions as a non-root user use the `--user` flag when interacting with `systemctl`.
+
+```
+$ systemctl --user start pod-systemd-pod.service
+$ podman pod ps
+POD ID         NAME          STATUS    CREATED          # OF CONTAINERS   INFRA ID
+0815c7b8e7f5   systemd-pod   Running   29 minutes ago   2                 6c5d116f4bbe
+$ sudo podman ps # 0 Number of pods on root.
+CONTAINER ID  IMAGE  COMMAND  CREATED  STATUS  PORTS  NAMES
+$ systemctl stop pod-systemd-pod.service
+$ podman pod ps
+POD ID         NAME          STATUS   CREATED          # OF CONTAINERS   INFRA ID
+272d2813c798   systemd-pod   Exited   29 minutes ago   2                 6c5d116f4bbe
+```
+
+Create a simple alpine container and generate the systemd unit file with `--new` flag.
+Enable the service and control operations using the systemctl commands.
+
+Note: When starting the container using `systemctl start` rather than altering the already running container it spins up a "new" container with similar configuration.
+
+```
+# Enable the service.
+
+$ sudo podman ps -a
+CONTAINER ID  IMAGE                            COMMAND  CREATED        STATUS     PORTS  NAMES
+bb310a0780ae  docker.io/library/alpine:latest  /bin/sh  2 minutes ago  Created           busy_moser
+$ sudo systemctl start container-busy_moser.service
+$ sudo podman ps -a
+CONTAINER ID  IMAGE                            COMMAND  CREATED        STATUS            PORTS      NAMES
+772df2f8cf3b  docker.io/library/alpine:latest  /bin/sh  1 second ago   Up 1 second ago              distracted_albattani
+bb310a0780ae  docker.io/library/alpine:latest  /bin/sh  3 minutes ago  Created                      busy_moser
+```
 ## SEE ALSO
-podman(1), podman-container(1), systemctl(1), systemd.unit(5), systemd.service(5)
+[podman(1)](podman.1.md), [podman-container(1)](podman-container.1.md), systemctl(1), systemd.unit(5), systemd.service(5)
 
 ## HISTORY
+April 2020, Updated details and added usecase to use generated .service files as root and non-root, by Sujil Shah (sushah at redhat dot com)
+
 August 2019, Updated with pod support by Valentin Rothberg (rothberg at redhat dot com)
+
 April 2019, Originally compiled by Brent Baude (bbaude at redhat dot com)