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Implement immutable base OS with overlay filesystem

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- Fix ext4 partition size calculation
- Mount root filesystem as read-only
- Add overlayfs on /var for writable runtime data
- Add tmpfs on /run for runtime files
- Update GRUB config to mount root as ro
- Update init to inform users about immutability

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot]
2025-12-29 19:49:52 +00:00
parent 726d59d765
commit f74390d632
2 changed files with 37 additions and 6 deletions
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17
scripts/docker-image-create-uefi.sh
View File

@@ -31,13 +31,13 @@ echo "Copying kernel to staging..."
cp $KERNEL_PATH /staging/esp/boot/vmlinuz
if [ -f "$INITRD_PATH" ]; then cp $INITRD_PATH /staging/esp/boot/initrd.img; fi
# Create GRUB configuration
# Create GRUB configuration for immutable root with overlay
printf '%s\n' \
'set timeout=3' \
'set default=0' \
'' \
'menuentry "SparkOS" {' \
' linux /boot/vmlinuz root=LABEL=SparkOS rw init=/sbin/init console=tty1 quiet' \
'menuentry "SparkOS (Immutable Base + Overlay)" {' \
' linux /boot/vmlinuz root=LABEL=SparkOS ro init=/sbin/init console=tty1 quiet' \
'}' \
> /staging/esp/boot/grub/grub.cfg
@@ -84,7 +84,14 @@ sgdisk -n 2:411648:0 -t 2:8300 -c 2:"Linux filesystem" /output/sparkos.img
# Extract partition regions using dd
echo "Extracting partition regions..."
dd if=/output/sparkos.img of=/tmp/esp.img bs=512 skip=2048 count=409600 2>/dev/null
dd if=/output/sparkos.img of=/tmp/root.img bs=512 skip=411648 2>/dev/null
# Calculate exact size for root partition
ROOT_START=411648
ROOT_END=$(sgdisk -p /output/sparkos.img | grep "^ 2" | awk '{print $3}')
ROOT_SIZE=$((ROOT_END - ROOT_START + 1))
echo "Root partition: start=$ROOT_START, end=$ROOT_END, size=$ROOT_SIZE sectors"
dd if=/output/sparkos.img of=/tmp/root.img bs=512 skip=$ROOT_START count=$ROOT_SIZE 2>/dev/null
# Format ESP partition (FAT32)
echo "Formatting EFI System Partition (FAT32)..."
@@ -111,7 +118,7 @@ mke2fs -t ext4 -L "SparkOS" -d /staging/root /tmp/root.img >/dev/null 2>&1
# Write partitions back to image
echo "Writing partitions to image..."
dd if=/tmp/esp.img of=/output/sparkos.img bs=512 seek=2048 count=409600 conv=notrunc 2>/dev/null
dd if=/tmp/root.img of=/output/sparkos.img bs=512 seek=411648 conv=notrunc 2>/dev/null
dd if=/tmp/root.img of=/output/sparkos.img bs=512 seek=$ROOT_START count=$ROOT_SIZE conv=notrunc 2>/dev/null
# Clean up temporary files
rm -f /tmp/esp.img /tmp/root.img

26
src/init.c
View File

@@ -100,6 +100,28 @@ int main(int argc, char *argv[]) {
fprintf(stderr, "Warning: Failed to mount /tmp\n");
}
// Set up overlay filesystem for immutable base OS
printf("Setting up overlay filesystem for writable layer...\n");
// Create overlay directories in tmpfs
if (system("mkdir -p /tmp/overlay/upper /tmp/overlay/work 2>/dev/null") != 0) {
fprintf(stderr, "Warning: Failed to create overlay directories\n");
}
// Mount overlay on /var for logs and runtime data
if (system("mount -t overlay overlay -o lowerdir=/var,upperdir=/tmp/overlay/upper,workdir=/tmp/overlay/work /var 2>/dev/null") != 0) {
fprintf(stderr, "Warning: Failed to mount overlay on /var - system may be read-only\n");
} else {
printf("Overlay filesystem mounted on /var (base OS is immutable)\n");
}
// Mount tmpfs on /run for runtime data
if (system("mkdir -p /run 2>/dev/null") == 0) {
if (system("mount -t tmpfs tmpfs /run 2>/dev/null") != 0) {
fprintf(stderr, "Warning: Failed to mount /run\n");
}
}
// Initialize network (wired only for bootstrap)
printf("Initializing wired network...\n");
if (system("/sbin/init-network 2>/dev/null") != 0) {
@@ -108,7 +130,9 @@ int main(int argc, char *argv[]) {
printf("Starting shell...\n");
printf("Welcome to SparkOS!\n");
printf("===================\n\n");
printf("===================\n");
printf("Base OS: Read-only (immutable)\n");
printf("Writable: /tmp, /var (overlay), /run\n\n");
// Main loop - keep respawning shell
while (1) {