OCPBUGS-62790: Resize /var tmpfs to 10GiB for ABI installations

Agent-based installations on vSphere with 16GB RAM were failing with "no
space left on device" errors during ostree image operations. The live
ISO environment uses a loopback filesystem mounted at /var that is
backed by a tmpfs sized at 50% of available RAM. On systems with 16GB
RAM, this provides only 8GB of tmpfs space.

During the bootstrap process, node-image-pull.sh creates a temporary
ostree repository in /var/ostree-container/repo to pull and apply the
node image. This operation has a peak tmpfs usage of approximately
8.5-9GB, exceeding the available 8GB and causing ENOSPC errors.

This fix resizes the /var tmpfs, the loopback backing file in it, and
the filesystem on it to 10GiB before creating the temporary ostree
repository, if the tmpfs was smaller than that. This provides sufficient
space for the image operations while maintaining compatibility with the
minimum 16GB RAM requirement.

The resize is performed using systemd-run to escape the mount namespace
of the node-image-pull service.

Author: zaneb

data/data/bootstrap/files/usr/local/bin/node-image-pull.sh.template

@@ -34,6 +34,11 @@ if test -f /run/ostree-live; then
     mkdir -p "${ostree_repo}"
     echo "In live environment; creating temporary repo to pull node image"
     ostree init --mode=bare --repo="${ostree_repo}"
+
+    echo "Resizing /run/ephemeral_base tmpfs to 10GiB for ostree operations..."
+    # Use systemd-run to avoid inheriting MountFlags
+    systemd-run --wait --service-type=oneshot /usr/local/bin/resize-ephemeral 10G
+
     # if there are layers, import all the content in the system repo for
     # layer-level deduping
     if [ -d /ostree/repo/refs/heads/ostree/container ]; then

data/data/bootstrap/files/usr/local/bin/resize-ephemeral.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -eu
+
+TARGET_SIZE="$1"
+BASE_DIR="/run/ephemeral_base"
+LOOPBACK_FILE="${BASE_DIR}/loopfs"
+
+function get_size_bytes() {
+    stat -f -c "%b * %s" "${BASE_DIR}"
+}
+
+TARGET_SIZE_BYTES="$(numfmt --from=iec "${TARGET_SIZE}")"
+CURRENT_SIZE_BYTES="$(get_size_bytes)"
+CURRENT_SIZE="$(numfmt --to=iec "${CURRENT_SIZE_BYTES}")"
+
+if ((TARGET_SIZE_BYTES > CURRENT_SIZE_BYTES)); then
+    echo "Expanding ephemeral base dir from ${CURRENT_SIZE} to ${TARGET_SIZE}"
+    mount -o remount,size="${TARGET_SIZE}" "${BASE_DIR}"
+
+    echo "Expanding ephemeral loopback"
+    truncate -s "$(get_size_bytes)" "${LOOPBACK_FILE}"
+
+    LOOPBACK_DEVICE="$(losetup -j "${LOOPBACK_FILE}" -O NAME -n)"
+    losetup -c "${LOOPBACK_DEVICE}"
+
+    echo "Expanding ephemeral filesystem"
+    xfs_growfs -d "${LOOPBACK_DEVICE}"
+else
+    echo "Ephemeral base dir size ${CURRENT_SIZE} is already larger than ${TARGET_SIZE}; not expanding"
+fi
+
+df -h