Testbed "bootblock" manipulator

cdrom/tbbootconfig/Makefile

+CFLAGS += -I. -g
+LDFLAGS += -lz
+
+tbbootconfig: tbbootconfig.c
+
+clean:
+	rm tbbootconfig

cdrom/tbbootconfig/testbed_boot.h

+/*
+ * EMULAB-COPYRIGHT
+ * Copyright (c) 2000-2002 University of Utah and the Flux Group.
+ * All rights reserved.
+ */
+
+#include <netinet/in.h>
+
+/*
+ * This structure is placed in the boot block. The loader reads the
+ * structure to determine whether it should boot from CDROM or switch
+ * to the disk.
+ *
+ * The basic idea is this:
+ *
+ * 1. The node always boots from the CD-ROM (first in boot chain).
+ * 2. The loader looks for this magic structure:
+ *     2a: If not present continues to load from the CD-ROM (step 4).
+ *     2b: If present check the contents of the structure. If directed to
+ *         boot from the disk goto step 3. If not, continues to load from
+ *         the CDROM (step 4).
+ * 3. Boot from the disk. Switch the boot device to the disk so that the
+ *    kernel is loaded from the disk. Also reset the flag (written to disk)
+ *    to indicate that next reboot should happen from the CDROM. Also set
+ *    another flag, cleared by the kernel, that indicates the kernel booted
+ *    okay. This avoids reboot loops in the case of a scrogged disk.
+ * 4. Boot from the CD-ROM. The user level code on the CD-ROM will take care
+ *    of the rest, writing the proper flags to the structure on the disk.
+ *    Normally, this means checking in with Emulab, and then setting the flag
+ *    to cause it to boot from the disk.
+ *
+ * This entire structure has to be less than a sector.
+ */
+#define SECSIZE			512
+#define TBBOOT_MAXIFACELEN	12
+#define TBBOOT_MAXHOSTLEN	32
+#define TBBOOT_MAXDOMAINLEN	64
+#define TBBOOT_MAXKEYLEN	64
+#define TBBOOT_MAXDISKDEVLEN	32
+
+typedef struct tbboot_header
+{
+	unsigned long		magic1;
+	short			version;
+
+	/*
+	 * Set bootfromdisk to 1 to force loader to boot from disk.
+	 */
+	char			bootfromdisk;
+
+	/*
+	 * Set bootfromcdrom to 0 when booting from the disk. The kernel
+	 * will set this to 1. If the cdrom boots with bootfromdisk 0
+	 * and bootfromcdrom 0, something went wrong and the kernel did not
+	 * boot properly. Avoids a loop.
+	 */
+	char			bootfromcdrom;
+
+	/*
+	 * Flag to indicate the image is valid. Clear this when writing
+	 * a new image, and set it when done.
+	 */
+	char			validimage;
+
+	/*
+	 * Flag to indicate the system config block is valid (has info).
+	 */
+	char			validconfig;
+
+	/*
+	 * crc32 from the zlib library.
+	 */ 
+	unsigned long		checksum;
+
+	/* Paranoia */
+	unsigned long		magic2;
+
+	/*
+	 * The emulab key. 
+	 */
+	char			emulabkey[TBBOOT_MAXKEYLEN];
+
+	/*
+	 * System configuration.
+	 */
+	struct {
+		char		interface[TBBOOT_MAXIFACELEN];
+		char		hostname[TBBOOT_MAXHOSTLEN];
+		char		domain[TBBOOT_MAXDOMAINLEN];
+		struct in_addr	IP;
+		struct in_addr	netmask;
+		struct in_addr	nameserver;
+		struct in_addr	gateway;
+	} sysconfig;
+} tbboot_t;
+
+/* Magic value identifying the header.  */
+#define TBBOOT_MAGIC1		0x9badbeef
+#define TBBOOT_MAGIC2		0x69ceafd8
+
+/* Current Version */
+#define TBBOOT_VERSION		100
+
+/*
+ * Offset from start of the disk. Hardwired to sector 60 which should be
+ * clear on our images.
+ */
+#define TBBOOT_SECTOR		60
+#define TBBOOT_OFFSET		(TBBOOT_SECTOR * SECSIZE)
+
+