Description of problem:

/usr/bin/chsh leaves the shell field of /etc/passwd blank, after the shell is
changed to /bin/sh.

In some ways this isn't a bug, since a null shell field is supposed to be
equivalent to /bin/sh.  But it seems strange for chsh to deliberately use null
instead of /bin/sh.

The vsftpd server will not run if the shell assigned to user "ftp" is a null
string. This may be a bug, or it may just be acceptable level of paranoia.

This problem was discovered when using  chsh -s /bin/sh ftp


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. chsh -s /bin/sh someuser
2. egrep '^someuser' /etc/passwd
3.
    
Actual results:
last field of passwd is blank

Expected results:
last field should contain /bin/sh

Additional info: