Re: Initrd or Cdrom as root

[Tigran Aivazian]

On Tue, 14 May 2002, Hans K. Rosbach wrote:

> Is there any way to dynamically load initrd or cdrom permanently as
> the root fs when booting from cdrom?
>
> My problem is that I need a reliable way to ALWAYS find the correct
> device to mount. Is there any way to make the kernel automagically
> mount the cdrom it booted from?

yes, just pass rootcd=1 as a boot command line option with the hack below
applied. Make sure that cdrom support is always compiled statically,
otherwise it will break.

--- 2418-/drivers/cdrom/cdrom.c	Fri Nov 16 18:14:08 2001
+++ 2418-rootparam/drivers/cdrom/cdrom.c	Tue Mar 12 00:29:54 2002
@@ -2480,6 +2480,11 @@
         return proc_dostring(ctl, write, filp, buffer, lenp);
 }

+kdev_t get_cdrom_dev(void)
+{
+	return topCdromPtr ? topCdromPtr->dev : 0;
+}
+
 /* Unfortunately, per device settings are not implemented through
    procfs/sysctl yet. When they are, this will naturally disappear. For now
    just update all drives. Later this will become the template on which
--- 2418-/init/main.c	Mon Feb 25 19:38:13 2002
+++ 2418-rootparam/init/main.c	Tue Mar 12 00:29:54 2002
@@ -311,6 +311,16 @@

 __setup("root=", root_dev_setup);

+static int rootcd_enable __initdata = 0;
+
+static int __init rootcd_setup(char *str)
+{
+	get_option(&str, &rootcd_enable);
+	return 1;
+}
+
+__setup("rootcd=", rootcd_setup);
+
 static int __init checksetup(char *line)
 {
 	struct kernel_param *p;
@@ -772,6 +782,10 @@
 	rd_load();
 #endif

+	if (rootcd_enable) {
+		extern kdev_t get_cdrom_dev(void);
+		ROOT_DEV = get_cdrom_dev();
+	}
 	/* Mount the root filesystem.. */
 	mount_root();