implement heuristic random filesystem filling. for boot its random modules + kernel, for root its recreation of FreeBSD's file structure, for stress testing purposes. The Makefile containts proper target doing all required steps to recreate disk image with 1 test partition and 2 real-life example EXT2 partitions.

.gitignore

@@ -1,2 +1,4 @@
+.vscode/
 obj/
 bin/
+mnt/

Makefile

@@ -2,6 +2,9 @@ CC					=	gcc
 CLFAGS				=	-g -Wall
 LDFLAGS				=	-g
 
+UID					:=	$(shell id -u)
+GID					:=	$(shell id -g)
+
 DISK				=	bin/disk.img
 DISK_SIZE			=	268435456
 DISK_LOOP			=	/dev/loop690
@@ -38,7 +41,10 @@ PART3_LOOP			=	/dev/loop693
 
 .PHONY: clean
 
-$(DISK):
+mnt:
+	mkdir mnt
+
+$(DISK): mnt
 	# create img file
 	truncate -s 256m $(DISK)
 	# format img file in MBR and create partitions
@@ -60,6 +66,18 @@ $(DISK):
 	sudo mkfs.ext2 -t $(PART2_FSTYPE) -L $(PART2_LABEL) -U $(PART2_UUID) $(PART2_LOOP)
 	sudo mkfs.ext2 -t $(PART3_FSTYPE) -L $(PART3_LABEL) -U $(PART3_UUID) $(PART3_LOOP)
 	# fill EXT2 partitions
+	# mount and fill boot partition
+	sudo mount $(PART2_LOOP) mnt/		# mount
+	sudo chown -R ${UID}:${GID} mnt/	# because we ain't gonna run python with root, so own it by user
+	python gen/generate_files.py --mode=boot --dirs=gen/rootfs-dirs.gz --path=mnt
+	sudo chown -R 0:0 mnt/				# make it root
+	sudo umount mnt/					# done
+	# mount and fill root partition
+	sudo mount $(PART3_LOOP) mnt/		# mount
+	sudo chown -R ${UID}:${GID} mnt/	# because we ain't gonna run python with root, so own it by user
+	python gen/generate_files.py --mode=root --dirs=gen/rootfs-dirs.gz --path=mnt
+	sudo chown -R 0:0 mnt/				# make it root
+	sudo umount mnt/					# done
 	# detach loopback devices
 	sudo losetup -d $(PART1_LOOP)
 	sudo losetup -d $(PART2_LOOP)

gen/generate_files.py

@@ -0,0 +1,53 @@
+import os
+import os.path
+import sys
+import gzip
+import string
+import random
+
+def get_arg(name):
+    return "".join(list(filter(lambda arg: arg.startswith(f"--{name}="), sys.argv))[0].split("=")[1:])
+
+def rand_string(strlen):
+    return ''.join(random.choice(string.ascii_lowercase) for x in range(strlen))
+
+def rand_file(fpath, size):
+    rand = open("/dev/urandom", "rb")
+    with open(fpath, "wb") as file:
+        file.write(rand.read(size))
+    rand.close()
+
+def fill_boot(path):
+    # fill modules dir
+    os.mkdir(os.path.join(path, "modules"))
+    for _ in range(24):
+        rand_file(os.path.join(path, "modules", rand_string(14)), random.randint(1024*3, 1024*1024))
+    # generate some configs
+    for _ in range(10):
+        rand_file(os.path.join(path, rand_string(8)), random.randint(16, 1024))
+    # write stage2 and kernel
+    rand_file(os.path.join(path, "stage2"), 8192)
+    rand_file(os.path.join(path, "kernel"), 1024*1024*16)
+
+def fill_root(path, dirs):
+    with gzip.open(dirs, "rt") as dirs:
+        for dir_path in dirs:
+            dir = dir_path[1:].strip()
+            if not dir: continue
+            os.mkdir(os.path.join(path, dir.strip()))
+
+
+if __name__ == "__main__":
+    path = get_arg("path")
+    dirs = get_arg("dirs")
+    mode = get_arg("mode")
+
+    if not os.path.exists(path):
+        sys.stderr.write("the mnt dir doesn't exists. preventing disaster")
+        sys.exit(1)
+
+    if mode == "boot": fill_boot(path)
+    elif mode == "root": fill_root(path, dirs)
+    else:
+        sys.stderr.write("unkown mode\n")
+        sys.exit(1)