Change index.md

Author: gwangmu

docs/software/container-engine/index.md

@@ -25,6 +25,9 @@ Through the EDF, container use cases can be abstracted to the point where end us
 ## Quick Start
 
 Let's set up a containerized Ubuntu 24.04 environment on the scratch folder (`${SCRATCH}`).
+
+### Step 1. Create EDF
+
 Save this file below as `ubuntu.toml` in `${HOME}/.edf` directory (the default location of EDF files).
 A more detailed explanation of each entry for the EDF can be seen in the [EDF reference][ref-ce-edf-reference].
 
@@ -34,36 +37,45 @@ mounts = ["/capstor/scratch/cscs/${USER}:/capstor/scratch/cscs/${USER}"]
 workdir = "/capstor/scratch/cscs/${USER}"
 ```
 
-
 !!! note
     Create `${HOME}/.edf` if the folder doesn't exist.
 
-Use Slurm in the cluster login node to start the environment above:
+### Step 2. Launch a program with EDF
+
+Use Slurm on the login node to launch a program inside the environment.
+Notice that the environment (EDF) is specified with the `--environment` option. 
+CE pulls the image automatically when the container starts.
 
 ```bash
-$ srun --environment=ubuntu --pty bash
+$ srun --environment=ubuntu echo "Hello" 
+Hello
 ```
 
-The terminal snippet below demonstrates how to launch a containerized environment using Slurm with the `--environment` option. 
-Notice that CE pulls the image automatically when the container starts.
+Or, use `--pty` to directly enter the environment.
 
-```console
-[daint-ln002]$ srun --environment=ubuntu --pty bash   # (1)
+```bash
+$ srun --environment=ubuntu --pty bash
+[compute-node]$ 
+```
 
-[nid005333]$ pwd                                      # (2)
-/capstor/scratch/cscs/<username>
+??? example "Entering the defined environment"
+    ```console
+    [daint-ln002]$ srun --environment=ubuntu --pty bash   # (1)
 
-[nid005333]$ cat /etc/os-release                      # (3)
-PRETTY_NAME="Ubuntu 24.04 LTS"
-NAME="Ubuntu"
-VERSION_ID="24.04"
-...
+    [nid005333]$ pwd                                      # (2)
+    /capstor/scratch/cscs/<username>
 
-[nid005333]$ exit                                     # (4)
-[daint-ln002]$
-```
+    [nid005333]$ cat /etc/os-release                      # (3)
+    PRETTY_NAME="Ubuntu 24.04 LTS"
+    NAME="Ubuntu"
+    VERSION_ID="24.04"
+    ...
+
+    [nid005333]$ exit                                     # (4)
+    [daint-ln002]$
+    ```
 
-1.  Starting an interactive shell session within the Ubuntu 24.04 container deployed on a compute node using `srun --environment=ubuntu --pty bash`.
-2.  Check the current folder (dubbed _the working directory_) is set to the user's scratch folder, as per EDF.
-3.  Show the OS version of your container (using `cat /etc/os-release`) based on Ubuntu 24.04 LTS.
-4.  Exiting the container (`exit`), returning to the login node.
+    1.  Starting an interactive shell session within the Ubuntu 24.04 container deployed on a compute node using `srun --environment=ubuntu --pty bash`.
+    2.  Check the current folder (dubbed _the working directory_) is set to the user's scratch folder, as per EDF.
+    3.  Show the OS version of your container (using `cat /etc/os-release`) based on Ubuntu 24.04 LTS.
+    4.  Exiting the container (`exit`), returning to the login node.