Update install_docker.sh for containerd configuration

## Summary
Fixes sed regex in containerd root configuration to use correct single backslash `\?` instead of double backslash `\\?`.

## Problem
The double backslash `\\?` in the sed pattern looks for a literal backslash character, not an optional `#`. This prevents the containerd root configuration from being uncommented and updated.

## Solution
Changed sed pattern from `^#\\?root` to `^#\?root` to correctly match optional `#` character.

## Testing
Verified on live cluster that:
- Double backslash `\\?` fails: `#root = "/var/lib/containerd"` (stays commented)
- Single backslash `\?` works: `root = "/opt/sagemaker/containerd/data-root"` (uncommented and updated)

## Changes
- Line 84: Containerd config for `/opt/sagemaker` with correct sed
- Line 101: Containerd config for `/opt/dlami/nvme` with correct sed

Fixes the issue reported in PR #914.

Author: PremiumSpider

1.architectures/5.sagemaker-hyperpod/LifecycleScripts/base-config/utils/install_docker.sh

@@ -66,6 +66,8 @@ sudo usermod -aG docker ubuntu
 # See: https://github.com/aws-samples/awsome-distributed-training/issues/127
 #
 # Docker workdir doesn't like Lustre. Tried with storage driver overlay2, fuse-overlayfs, & vfs.
+# Also, containerd ships with a commented root in its default config; we need to ensure an
+# uncommented root that points to the fast local volume.
 if [[ $(mount | grep /opt/sagemaker) ]]; then
     cat <<EOL >> /etc/docker/daemon.json
 {
@@ -76,6 +78,13 @@ EOL
     sed -i \
         's|^\[Service\]$|[Service]\nEnvironment="DOCKER_TMPDIR=/opt/sagemaker/docker/tmp"|' \
         /usr/lib/systemd/system/docker.service
+
+    # Ensure containerd config exists and point its root to /opt/sagemaker
+    if [[ ! -f /etc/containerd/config.toml ]]; then
+        containerd config default | sudo tee /etc/containerd/config.toml >/dev/null
+    fi
+    sudo sed -i -e 's|^#\?root *=.*|root = "/opt/sagemaker/containerd/data-root"|' \
+        /etc/containerd/config.toml
 elif [[ $(mount | grep /opt/dlami/nvme) ]]; then
     cat <<EOL >> /etc/docker/daemon.json
 {
@@ -86,7 +95,21 @@ EOL
     sed -i \
         's|^\[Service\]$|[Service]\nEnvironment="DOCKER_TMPDIR=/opt/dlami/nvme/docker/tmp"|' \
         /usr/lib/systemd/system/docker.service
+
+    # Ensure containerd config exists and point its root to /opt/dlami/nvme
+    if [[ ! -f /etc/containerd/config.toml ]]; then
+        containerd config default | sudo tee /etc/containerd/config.toml >/dev/null
+    fi
+    sudo sed -i \
+        -e 's|^#\?root *=.*|root = "/opt/dlami/nvme/docker/containerd"|' \
+        /etc/containerd/config.toml
 fi
 
 systemctl daemon-reload
-systemctl restart docker
+systemctl restart docker
+
+echo "
+###################################
+# END: install docker
+###################################
+"