on a deeper look at this issue, another astounding
(read confusing, erroneous) detail was revealed ...
consider a kernel boot cmdline like
"root=/dev/vg/slash ro"
which could be used to boot from a LVM LV named slash
or, if you prefer a physical device (using devfs)
"root=/dev/ide//host0/bus0/target0/lun0/part1 ro"
now what happens on boot is:
root_dev_setup() is called with "root=" and, in turn
calls name_to_kdev_t() which searches root_dev_names[]
for the given device names, which of course, can not
be found, because they are not listed, so ROOT_DEV
becomes (0:0)
if you have CONFIG_ROOT_NFS enabled, then mount_root()
will check if MAJOR(ROOT_DEV) == UNNAMED_MAJOR, which
will be true, although root=/dev/nfs (0:ff) wasn't
specified, leading directly to "Unable to mount root
fs via NFS, trying floppy." and the Floppy Fallback,
instead of booting from your specified root device.
"root=/dev/hda1 ro"
will work as expected, because it will be found in
root_dev_names[] ...
I suggest to do one fix, and one improvement ...
and of course this _will_ break the current behaviour
you won't be able to use root=tux (or your favorite
pet name) to have root on nfs ...
what do you think?
best,
Herbert
------------------ FIX
diff -NurbP --minimal linux-2.4.21/init/do_mounts.c linux-2.4.21-ffb/init/do_mounts.c
--- linux-2.4.21/init/do_mounts.c Fri Jun 13 17:49:28 2003
+++ linux-2.4.21-ffb/init/do_mounts.c Thu Jun 19 17:41:35 2003
@@ -747,7 +747,8 @@
static void __init mount_root(void)
{
#ifdef CONFIG_ROOT_NFS
- if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
+ if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR
+ && MINOR(ROOT_DEV) == 255) {
if (mount_nfs_root()) {
sys_chdir("/root");
ROOT_DEV = current->fs->pwdmnt->mnt_sb->s_dev;
maybe a NFS_MAJOR, NFS_MINOR would be more descriptive here ...
------------------ SECURITY IMPROVEMENT ;)
diff -NurbP --minimal linux-2.4.21/fs/Config.in linux-2.4.21-ffb/fs/Config.in
--- linux-2.4.21/fs/Config.in Tue Dec 10 03:25:19 2002
+++ linux-2.4.21-ffb/fs/Config.in Thu Jun 19 17:42:35 2003
@@ -103,6 +103,7 @@
dep_tristate 'NFS file system support' CONFIG_NFS_FS $CONFIG_INET
dep_mbool ' Provide NFSv3 client support' CONFIG_NFS_V3 $CONFIG_NFS_FS
dep_bool ' Root file system on NFS' CONFIG_ROOT_NFS $CONFIG_NFS_FS $CONFIG_IP_PNP
+ dep_bool ' Disable Floppy Fallback' CONFIG_NO_FLOPPY_FALLBACK $CONFIG_ROOT_NFS
dep_tristate 'NFS server support' CONFIG_NFSD $CONFIG_INET
dep_mbool ' Provide NFSv3 server support' CONFIG_NFSD_V3 $CONFIG_NFSD
diff -NurbP --minimal linux-2.4.21/init/do_mounts.c linux-2.4.21-ffb/init/do_mounts.c
--- linux-2.4.21/init/do_mounts.c Fri Jun 13 17:49:28 2003
+++ linux-2.4.21-ffb/init/do_mounts.c Thu Jun 19 17:41:35 2003
@@ -754,8 +754,10 @@
printk("VFS: Mounted root (nfs filesystem).\n");
return;
}
+# ifndef CONFIG_NO_FLOPPY_FALLBACK
printk(KERN_ERR "VFS: Unable to mount root fs via NFS, trying floppy.\n");
ROOT_DEV = MKDEV(FLOPPY_MAJOR, 0);
+# endif
}
#endif
devfs_make_root(root_device_name);
-
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This archive was generated by hypermail 2b29 : Mon Jun 23 2003 - 22:00:29 EST