Description of problem:

We have a number of hosts that share home dirs over NFS using a scheme whereby /
u/host is automounted from hostname:/home/users.  That is, the real home 
directory is hostname:/home/users/username, but in the password file the home 
dir is listed as /u/hostname/username, and automount takes care of making them 
the same, even on the host where the directory resides.

Recently I moved some users who were irregularly placed in /home to /home/users 
and discovered the following:

The behavior of "usermod -d newdir -m userid" differs depending on whether the 
real dir or the automounted synonym is used:
"usermod -d /home/users/userid -m userid" preserves the modtimes of the user's 
files
"usermod -d /u/host/userid -m userid" changes the modtimes of all the files to 
the time of the move.

I don't see why this should happen, since mv preserves modtimes, even when the 
destination directory is aliased via automount this way.


Version-Release number of selected component (if applicable):
shadow-utils-4.0.18.1-15.fc7

How reproducible: 
Always


Steps to Reproduce:
1. Create a partition, e.g. /home.  Create a subdirectory /home/users
2. Create an automount entry in /etc/auto.home saying "* &:/home/users".  Make 
sure that /u/hostname shows the same contents as /home/users, where hostname is 
the name (without domain) of the local host.  You do not need to create an 
entry in /etc/exports since this test is done on the local host.  The behavior 
of usermod is the same whether /home/users is exported or not.
3. Use "useradd -d /home/testuser testuser" to create a user with home dir /
home/testuser.  Populate with some files and use touch to backdate them, or 
else wait a little while so the next step will occur at a noticeably different 
system time than the file creations.  Use "ls -l ~testuser" to see the modtimes.
4. Use "usermod -d /home/users/testuser -m testuser" to move the user's home 
dir.  Use "ls -l ~testuser" to see that the file modtimes are unchanged.
5. Use "usermod -d /home/testuser -m testuser" to move the home dir back.  Use 
"ls -l ~testuser" to verify that modtimes are still unchanged.
6. Now use "usermod -d /u/hostname/testuser -m testuser" to move the user's 
home dir to /u/hostname/testuser which is the same as /home/users/testuser. Use 
"ls -l ~testuser" to see the modtimes of the files, now changed to that of the 
time at which step 4 was executed.
7. To show that this does not need to happen, find any file and use "mv file /u/
hostname/" and see its modtime is not changed.
  
Actual results:
Modtimes of user's files become those of the usermod execution.

Expected results:
Modtimes of user's files should be unchanged by the move.

Additional info: The workaround for this bug is to use /home/users/testuser in 
the usermod command, then use vipw to change the home dir to /u/hostname/
testuser in /etc/passwd.