update gitignore

fix: localize the code for current system environment

.gitignore

@@ -0,0 +1,7 @@
+rootfs/
+
+*.exe
+*.out
+
+container-from-scratch
+

container-from-scratch.c

@@ -22,6 +22,7 @@
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
+#include <sys/sysmacros.h>
 #include <sys/utsname.h>
 #include <sys/wait.h>
 #include <linux/capability.h>
@@ -142,6 +143,31 @@ int mounts(struct child_config *config)
 		return -1;
 	}
 	fprintf(stderr, "done.\n");
+
+	fprintf(stderr, "=> mounting /proc...");
+	if (mount("proc", "/proc", "proc", 0, NULL)) {
+		fprintf(stderr, "failed: %m\n");
+		return -1;
+	}
+	fprintf(stderr, "done.\n");
+
+	fprintf(stderr, "=> mounting /dev...");
+	if (mount("tmpfs", "/dev", "tmpfs", MS_NOSUID | MS_STRICTATIME, "mode=755,size=65536k")) {
+		fprintf(stderr, "failed: %m\n");
+		return -1;
+	}
+	umask(0);
+	if (mknod("/dev/null", S_IFCHR | 0666, makedev(1, 3))) {
+		fprintf(stderr, "mknod null failed: %m\n");
+	}
+	if (mknod("/dev/zero", S_IFCHR | 0666, makedev(1, 5))) {
+		fprintf(stderr, "mknod zero failed: %m\n");
+	}
+	if (mknod("/dev/urandom", S_IFCHR | 0666, makedev(1, 9))) {
+		fprintf(stderr, "mknod urandom failed: %m\n");
+	}
+	fprintf(stderr, "done.\n");
+
 	return 0;
 }
 
@@ -248,17 +274,6 @@ struct cgrp_control *cgrps[] = {
 			NULL
 		}
 	},
-	& (struct cgrp_control) {
-		.control = "blkio",
-		.settings = (struct cgrp_setting *[]) {
-			& (struct cgrp_setting) {
-				.name = "blkio.weight",
-				.value = PIDS
-			},
-			&add_to_tasks,
-			NULL
-		}
-	},
 	NULL
 };
 int resources(struct child_config *config)
@@ -504,8 +519,8 @@ finish_options:
 		fprintf(stderr, "weird release format: %s\n", host.release);
 		goto cleanup;
 	}
-	if (major != 4 || (minor != 7 && minor != 8)) {
-		fprintf(stderr, "expected 4.7.x or 4.8.x: %s\n", host.release);
+	if (major < 4 || (major == 4 && minor < 7)) {
+		fprintf(stderr, "kernel too old: %s (need >= 4.7)\n", host.release);
 		goto cleanup;
 	}
 	if (strcmp("x86_64", host.machine)) {