Make the hello image leaner

[NO TESTS NEEDED]

Change from using a bash script to a c file
for running the image.  With thanks to discussions
with @afbjorklund, the Containerfile was rigged
up to make the final image be only KB's in size.

Also add USER 1000 to make the image test/run as
non-root, and update the README.md

Signed-off-by: tomsweeneyredhat <tsweeney@redhat.com>

1 files changed, 25 insertions, 3 deletions

diff --git a/contrib/helloimage/README.md b/contrib/helloimage/README.md
index 93edcc527..ca69f87b4 100644
--- a/contrib/helloimage/README.md
+++ b/contrib/helloimage/README.md
@@ -19,7 +19,7 @@ Using this image is helpful to:
 
 The contents of this directory contain:
  * ./Containerfile
- * ./podman_hello_world.bash
+ * ./podman_hello_world.c
 
 ## Sample Usage
 
@@ -28,7 +28,7 @@ To simply run the image:
 ```
 podman run quay.io/podman/hello
 
-! ... Hello Podman World ...!
+!... Hello Podman World ...!
 
          .--"--.
        / -     - \
@@ -49,7 +49,29 @@ To build the image yourself, copy the files from this directory into
 a local directory and issue these commands:
 
 ```
-chmod 755 ./podman_hello_world.bash
 podman build -t myhello .
 podman run myhello
 ```
+
+## Potential Issues:
+
+The image runs as a rootless user with the UID set to `1000`.
+If the /etc/subuid and /etch/subgid values are not set appropriately to run as a
+rootless user on the host, an error like this might be raised:
+
+```
+Copying blob acab339ca1e8 done
+ERRO[0002] Error while applying layer: ApplyLayer exit status 1 stdout:  stderr: potentially insufficient UIDs or GIDs available in user namespace (requested 0:12 for /var/spool/mail): Check /etc/subuid and /etc/subgid: lchown /var/spool/mail: invalid argument
+Error: writing blob: adding layer with blob "sha256:ee0cde9de8a68f171a8c03b0e9954abf18576947e2f3187e84d8c31ccd8f6a09": ApplyLayer exit status 1 stdout:  stderr: potentially insufficient UIDs or GIDs available in user namespace (requested 0:12 for /var/spool/mail): Check /etc/subuid and /etc/subgid: lchown /var/spool/mail: invalid argument
+```
+
+Please refer to this [blog post](https://www.redhat.com/sysadmin/rootless-podman) for further configuration information.
+
+## THANKS!
+
+Many Thanks to @afbjorklund for a great discussion during the
+first revision of this container image that resulted in moving
+from using bash to using C, and the ensuing changes to the
+Containerfile.
+
+Also many thanks to @mairin for the awesome ASCII art!