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update-alternatives: use 'ln -n'
Using the '-n' option (--no-dereference) is a better way to solve the
do-not-link-into-directory issue. Using only 'ln -sf' can cause problems
on SELinux enabled hosts when target is inaccessible; e.g. when preparing
an offline rootsystem:
| $ cd <offline root>
| $ ln -sf /lib/systemd/systemd sbin/init # alternative #1
| $ ln -sf /bin/busybox sbin/init # alternative #2
| ln: accessing `sbin/init': Permission denied
|
| --> strace:
| brk(0) = 0x102b000
| stat("sbin/init", 0x7fffaa91c900) = -1 EACCES (Permission denied)
| ...
| exit_group(1) = ?
Now with '-n':
| $ ln -snf /bin/busybox sbin/init
| lstat("sbin/init", {st_mode=S_IFLNK|0777, st_size=20, ...}) = 0
| lstat("sbin/init", {st_mode=S_IFLNK|0777, st_size=20, ...}) = 0
| stat("/bin/busybox", 0x7fff8c1a3bd0) = -1 ENOENT (No such file or directory)
| symlink("/bin/busybox", "sbin/init") = -1 EEXIST (File exists)
| unlink("sbin/init") = 0
| symlink("/bin/busybox", "sbin/init") = 0
The '-n' flag is well supported (coreutils have it at least since
1999, busybox at least since 0.60.3 (2002)) and it obsoletes the
explicit check whether target is a directory.
Upstream-Status: pending [http://code.google.com/p/opkg/issues/detail?id=95]
Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Index: trunk/utils/update-alternatives.in
===================================================================
--- trunk.orig/utils/update-alternatives.in
+++ trunk/utils/update-alternatives.in
@@ -113,14 +113,7 @@ find_best_alt() {
if [ ! -d $link_dir ]; then
mkdir -p $link_dir
fi
- if [ -h $link -a -d $link ]; then
- # If $link exists and the target is a directory,
- # 'ln -sf $path $link' doesn't replace the link to
- # that directory, it creates new link inside.
- echo "update-alternatives: Removing $link".
- rm -f $link
- fi
- ln -sf $path $link
+ ln -snf $path $link
echo "update-alternatives: Linking $link to $path"
else
echo "update-alternatives: Error: not linking $link to $path since $link exists and is not a link"
|
