There are multiple problems with grub-reboot/savedefault/default=saved.
1: grub-reboot doesn't restore the default after rebooting, making it
effectively equivalent to grub-set-default. This is because the
savedefault functionality currently saves the entry you boot from as the
new default even when grub-reboot is used. Because of problem #2 there is
no way ( outside manually editing the grub.cfg ) to use grub-reboot without
savedefault functionality also enabled ( and thus no configuration where
grub-reboot isn't broken ). I've added a patch for this to
the bug report @ http://savannah.gnu.org/bugs/?28161 and as the first patch
attached to this email.
2: Setting GRUB_DEFAULT=saved in /etc/default/grub also enables savedefault
functionality. There are many people who would want to use grub-reboot and
grub-set-default without savedefault. The second patch adds a separate
variable, GRUB_SAVEDEFAULT, for enabling savedefault.
3: Savedefault functionality currently adds two lines ( one setting a
variable, the other saving it ) to every menu entry and with my patch for
fixing grub-reboot, an if statement as well. This clutters the menu entries
and makes it hard to write and maintain custom menu entries with
savedefault. The third patch moves this to a function "savedefault" defined
in 00_header so entries just have to have "savedefault", like in grub
legacy. And if the implementation of savedefault needs to change, custom
menu entries will still work unmodified.
4: Even with the first grub-reboot fix the default is still not restored
when grubenv is not writable ( /boot on lvm for example ). Since
grub-reboot can't work without a writable grubenv it's at least safer to
boot into the "real" default instead of the "temporary" default. The
fourth patch sets default=$prev_saved_default if save_env fails.
Grub-reboot ( the utility ) should also complain when grubenv isn't
writable by grub. What is the best way to determine that grubenv likely is
or isn't writable by grub?
5: Since grub2 uses menu entry titles for savedefault instead of numbers,
the default kernel booted won't be changed when the user installs a new
kernel. Using titles instead of numbers is good, but an unfortunate
consequence that users may not realize ( and was not true with savedefault
in grub-legacy ) is that if users set GRUB_SAVEDEFAULT=true they will never
actually boot any updated kernels unless they select them manually at the
grub menu. This could lead to not getting security updates for the kernel,
and with major upgrades could cause serious problems when the old kernel
doesn't work with newer userland components like Xorg. I can't think of a
good way to solve this problem.
--
Jordan Uggla ( Jordan_U on irc.freenode.net )
=== modified file 'util/grub-mkconfig_lib.in'
--- old/util/grub-mkconfig_lib.in 2009-12-09 21:03:26 +0000
+++ new/util/grub-mkconfig_lib.in 2009-12-16 20:12:30 +0000
@@ -97,8 +97,10 @@
save_default_entry ()
{
if [ "x${GRUB_DEFAULT}" = "xsaved" ] ; then
- echo 'saved_entry=${chosen}'
- echo 'save_env saved_entry'
+ echo 'if [ ${boot_once} != true ]; then'
+ echo ' saved_entry=${chosen}'
+ echo ' save_env saved_entry'
+ echo 'fi'
fi
}
=== modified file 'util/grub.d/00_header.in'
--- old/util/grub.d/00_header.in 2009-11-24 00:22:41 +0000
+++ new/util/grub.d/00_header.in 2009-12-16 20:12:30 +0000
@@ -46,6 +46,7 @@
save_env saved_entry
prev_saved_entry=
save_env prev_saved_entry
+ boot_once=true
fi
EOF
=== modified file 'util/grub-mkconfig.in'
--- old/util/grub-mkconfig.in 2009-12-12 00:43:32 +0000
+++ new/util/grub-mkconfig.in 2009-12-16 20:22:36 +0000
@@ -220,7 +220,8 @@
GRUB_DISABLE_LINUX_UUID \
GRUB_DISABLE_LINUX_RECOVERY \
GRUB_GFXMODE \
- GRUB_DISABLE_OS_PROBER
+ GRUB_DISABLE_OS_PROBER \
+ GRUB_SAVEDEFAULT
if test "x${grub_cfg}" != "x"; then
rm -f ${grub_cfg}.new
=== modified file 'util/grub-mkconfig_lib.in'
--- old/util/grub-mkconfig_lib.in 2009-12-16 20:12:30 +0000
+++ new/util/grub-mkconfig_lib.in 2009-12-16 20:22:36 +0000
@@ -96,7 +96,7 @@
save_default_entry ()
{
- if [ "x${GRUB_DEFAULT}" = "xsaved" ] ; then
+ if [ "x${GRUB_SAVEDEFAULT}" = "xtrue" ] ; then
echo 'if [ ${boot_once} != true ]; then'
echo ' saved_entry=${chosen}'
echo ' save_env saved_entry'
=== modified file 'util/grub-mkconfig_lib.in'
--- old/util/grub-mkconfig_lib.in 2009-12-16 20:22:36 +0000
+++ new/util/grub-mkconfig_lib.in 2009-12-16 20:25:37 +0000
@@ -97,10 +97,7 @@
save_default_entry ()
{
if [ "x${GRUB_SAVEDEFAULT}" = "xtrue" ] ; then
- echo 'if [ ${boot_once} != true ]; then'
- echo ' saved_entry=${chosen}'
- echo ' save_env saved_entry'
- echo 'fi'
+ echo 'savedefault'
fi
}
=== modified file 'util/grub.d/00_header.in'
--- old/util/grub.d/00_header.in 2009-12-16 20:12:30 +0000
+++ new/util/grub.d/00_header.in 2009-12-16 20:25:37 +0000
@@ -48,6 +48,14 @@
save_env prev_saved_entry
boot_once=true
fi
+
+function savedefault {
+ if [ \${boot_once} != true ]; then
+ saved_entry=\${chosen}
+ save_env saved_entry
+ fi
+}
+
EOF
case ${GRUB_TERMINAL_INPUT}:${GRUB_TERMINAL_OUTPUT} in
=== modified file 'util/grub.d/00_header.in'
--- old/util/grub.d/00_header.in 2009-12-16 20:25:37 +0000
+++ new/util/grub.d/00_header.in 2009-12-16 20:41:14 +0000
@@ -43,10 +43,13 @@
set default=${GRUB_DEFAULT}
if [ \${prev_saved_entry} ]; then
saved_entry=\${prev_saved_entry}
- save_env saved_entry
- prev_saved_entry=
- save_env prev_saved_entry
- boot_once=true
+ if save_env saved_entry; then
+ prev_saved_entry=
+ save_env prev_saved_entry
+ boot_once=true
+ else
+ default=\${prev_saved_entry}
+ fi
fi
function savedefault {
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