Resolving symllinks in grub-install

[Pavel Roskin]

Hello!

I tried to install GRUB (fresh from CVS) on a system which has a 
kernel with devfs but uses old-style names in /etc/fstab (/dev/hda1 and so 
on).  I had no problems with that system except that GRUB refused to 
install on it.

It turns out that "df" (from fileutils-4.1) behaves inconsistently
dependent on the arguments - sometimes it returns the symlink name,
sometimes the full name.

This patch fixes the problem by resolving symlinks.  A new function, 
resolve_links() takes a variable name as an argument.  It takes the 
filename from the variable, resolves it until it becomes a real file, not 
a symlink, and puts the result to the same variable.

I was able to install GRUB on that system after applying this patch.

If anybody wants, I can go one step further to include "df" into that
function, making it a function to determine the block device for the given
file.

==================================
--- ChangeLog
+++ ChangeLog
@@ -1 +1,8 @@
+2002-02-08  Pavel Roskin  <address@hidden>
+
+       * util/grub-install.in (resolve_links): New function to resolve
+       symlinks.  Use it for root_device, bootdir_device and
+       grubdir_device to fix comparing them on Linux with devfs and old
+       names in /etc/fstab.
+
 2002-02-08  Yoshinori K. Okuji  <address@hidden>
--- util/grub-install.in
+++ util/grub-install.in
@@ -175,6 +175,30 @@
     fi
 }
 
+# Usage: resolve_links variable
+# Resolve symbolic link, make the filename absolute.
+# "variable" holds the filename to be resolved (on input and output).
+resolve_links () {
+    var="$1"
+    eval "fname=\$$var"
+
+    # Normalize filename
+    case $fname in
+       /*) ;;
+       *) fname="`pwd`/$fname"
+    esac
+
+    while test -h $fname; do
+       new_fname=`readlink $fname`
+       # Convert relative symlinks
+       case $new_fname in
+           /*) fname="$new_fname" ;;
+           *) fname="`echo $fname | sed 's%/[^/]*$%%'`/$new_fname" ;;
+       esac
+    done
+    eval "$var=$fname"
+}
+
 # Check the arguments.
 for option in "$@"; do
     case "$option" in
@@ -315,6 +339,9 @@
 bootdir_device=`df ${bootdir} | grep /dev/ \
     | sed 's%.*\(/dev/[^       ]*\).*%\1%'`
 
+resolve_links root_device
+resolve_links bootdir_device
+
 # Check if the boot directory is in the same device as the root directory.
 if test "x$root_device" != "x$bootdir_device"; then
     # Perhaps the user has a separate boot partition.
@@ -332,6 +359,9 @@
 # directory.
 grubdir_device=`df ${grubdir} | grep /dev/ \
     | sed 's%.*\(/dev/[^       ]*\).*%\1%'`
+
+resolve_links grubdir_device
+
 if test "x$grubdir_device" != "x$root_device"; then
     # For now, cannot deal with this situation.
     cat <<EOF 1>&2
==================================

-- 
Regards,
Pavel Roskin