setup-rootfs

#!/bin/bash
set -e

ROOTFS="${1:-rootfs.ext4}"
AGENT_BIN="${2:-onfire-agent}"
MOUNTPOINT="/tmp/rootfs-setup-$$"

if [ ! -f "$ROOTFS" ]; then
    echo "Error: rootfs not found: $ROOTFS" >&2
    exit 1
fi

echo "==> Setting up rootfs: $ROOTFS"

# Expand base image to 1GB so there's room to install packages
echo "==> Expanding rootfs to 1GB..."
truncate -s 1G "$ROOTFS"
e2fsck -f -y "$ROOTFS" > /dev/null 2>&1 || true
resize2fs "$ROOTFS" > /dev/null 2>&1

mkdir -p "$MOUNTPOINT"

sudo mount -o loop "$ROOTFS" "$MOUNTPOINT"
trap "sudo umount -l $MOUNTPOINT/dev/pts 2>/dev/null; sudo umount -l $MOUNTPOINT/proc 2>/dev/null; sudo umount -l $MOUNTPOINT/sys 2>/dev/null; sudo umount -l $MOUNTPOINT/dev 2>/dev/null; sudo umount -l $MOUNTPOINT 2>/dev/null; sudo rmdir $MOUNTPOINT 2>/dev/null" EXIT

# Bind mount host proc/sys/dev and resolv.conf so chroot has networking and /proc
sudo mount --bind /proc "$MOUNTPOINT/proc"
sudo mount --bind /sys "$MOUNTPOINT/sys"
sudo mount --bind /dev "$MOUNTPOINT/dev"
sudo mount --bind /dev/pts "$MOUNTPOINT/dev/pts"
sudo cp /etc/resolv.conf "$MOUNTPOINT/etc/resolv.conf"

# Set root password
echo "==> Setting root password to 'root'..."
echo "root:root" | sudo chroot "$MOUNTPOINT" chpasswd

# Use a drop-in so it wins over any default that disables password auth
echo "==> Configuring SSH for password login..."
sudo mkdir -p "$MOUNTPOINT/etc/ssh/sshd_config.d"
cat <<'EOF' | sudo tee "$MOUNTPOINT/etc/ssh/sshd_config.d/99-onfire.conf" > /dev/null
PermitRootLogin yes
PasswordAuthentication yes
UseDNS no
EOF

# Enable SSH service
echo "==> Enabling SSH service..."
sudo chroot "$MOUNTPOINT" systemctl enable ssh > /dev/null 2>&1 || true

# Install onfire-agent
if [ -f "$AGENT_BIN" ]; then
    echo "==> Installing onfire-agent..."
    sudo cp "$AGENT_BIN" "$MOUNTPOINT/usr/local/bin/onfire-agent"
    sudo chmod +x "$MOUNTPOINT/usr/local/bin/onfire-agent"

    # Install systemd service unit
    cat <<'UNIT' | sudo tee "$MOUNTPOINT/etc/systemd/system/onfire-agent.service" > /dev/null
[Unit]
Description=Onfire Fault Injection Agent
After=network.target

[Service]
ExecStart=/usr/local/bin/onfire-agent
Restart=always
RestartSec=2
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target
UNIT

    sudo chroot "$MOUNTPOINT" systemctl enable onfire-agent > /dev/null 2>&1 || true
    echo "  ✓ onfire-agent installed and enabled"
else
    echo "  (skipping onfire-agent: $AGENT_BIN not found)"
fi

# Install stress-ng for realistic CPU fault injection (best-effort)
echo "==> Installing stress-ng (optional, improves CPU fault accuracy)..."
sudo chroot "$MOUNTPOINT" apt-get install -y --no-install-recommends stress-ng > /dev/null 2>&1 && \
    echo "  ✓ stress-ng installed" || \
    echo "  (stress-ng install failed — CPU faults will use pure-Go fallback)"

echo "✓ Rootfs setup complete!"