[CentOS] nsswitch.conf, ldap, local groups problem

Craig White craigwhite at azapple.com
Wed Aug 27 21:44:24 UTC 2008


On Wed, 2008-08-27 at 17:35 -0400, Mark Hennessy wrote:
> Quoting Craig White <craigwhite at azapple.com>:
> 
> > On Wed, 2008-08-27 at 17:07 -0400, Mark Hennessy wrote:
> >> Quoting Craig White <craigwhite at azapple.com>:
> >>
> >> > On Wed, 2008-08-27 at 14:53 -0400, Mark Hennessy wrote:
> >> >> Quoting Craig White <craigwhite at azapple.com>:
> >> >>
> >> >> > On Wed, 2008-08-27 at 12:34 -0400, Mark Hennessy wrote:
> >> >> >> I'm using CentOS 5.0,5.1, and 5.2 on several systems where I'm seeing
> >> >> >> this problem.
> >> >> >>
> >> >> >> Hello, I'm seeing a weird problem that perhaps someone has run into
> >> >> >> with groups.
> >> >> >>
> >> >> >> First, a little background.
> >> >> >> I was made aware of a problem with CentOS 5 where if the nscd password
> >> >> >> cache is clear and
> >> >> >> someone tries to log in if there is no network connection with an LDAP
> >> >> >> account that it
> >> >> >> just hangs.  Even worse, if the machine is rebooted and it continues
> >> >> >> to have no network
> >> >> >> connection, even root login doesn't work.  I messed around with
> >> >> >> nsswitch.conf to fix this
> >> >> >> problem.
> >> >> >>
> >> >> >> I altered these lines as so:
> >> >> >> passwd:     files [!NOTFOUND=return] ldap
> >> >> >> shadow:     files [!NOTFOUND=return] ldap
> >> >> >> group:      files [!NOTFOUND=return] ldap
> >> >> >>
> >> >> >> and the problem seemed to go away.
> >> >> >>
> >> >> >> But now, here's the weird stuff:
> >> >> >> I have defined in my local /etc/groups file this line:
> >> >> >> group1:x:100:apache
> >> >> >> group2:x:101:apache
> >> >> >>
> >> >> >> 'getent group groupname' shows the right info:
> >> >> >> # getent group group1
> >> >> >> group1:x:100:apache
> >> >> >>
> >> >> >> # sudo -u apache bash
> >> >> >> $ groups
> >> >> >> apache
> >> >> >>
> >> >> >> I revert back to my old config:
> >> >> >> # sudo -u apache bash
> >> >> >> $ groups
> >> >> >> apache group1 group2
> >> >> >>
> >> >> >> Also, something else that's interesting. If I do this:
> >> >> >> passwd:     files [!NOTFOUND=return] ldap
> >> >> >> shadow:     files [!NOTFOUND=return] ldap
> >> >> >> group:      ldap [NOTFOUND=continue] files
> >> >> >>
> >> >> >> and reboot, udev segfaults and the system freezes up after a few
> >> >> >> more seconds.
> >> >> >> Starting udev: /sbin/start_udev: line 43:   519 Segmentation fault
> >> >> >>   "$@" $ARGS
> >> >> >> /sbin/start_udev: line 201:   523 Segmentation fault        
> >> /sbin/udevd -d
> >> >> >> Wait timeout. Will continue in the background.[FAILED]
> >> >> >>
> >> >> >> Any advice?
> >> >> > ----
> >> >> > Try putting this at the bottom of /etc/ldap.conf
> >> >> >
> >> >> > timelimit 30
> >> >> > bind_timelimit 30
> >> >> > bind_policy soft
> >> >> > nss_initgroups_ignoreusers root,ldap
> >> >> >
> >> >> > I wouldn't recommend the changes that you have in nsswitch.conf
> >> >>
> >> >> Unfortunately, that doesn't work either.
> >> >> I made the changes, shut down the machine and started it without
> >> >> networking, and here's what happens:
> >> >>
> >> >> login: root
> >> >> Password:
> >> >>
> >> >> login:
> >> >>
> >> >> login pukes and init starts it again.
> >> > ----
> >> > you shouldn't need to restart but if you can't login as root, you
> >> > probably still have something messed up in /etc/nsswitch.conf or may
> >> > have messed up /etc/passwd | /etc/shadow
> >> >
> >> > can you login as a user and su - to root?
> >> >
> >> > if not, it probably would be best to boot to runlevel 1 and
> >> > edit /etc/nsswitch.conf so it has this...
> >> >
> >> > passwd:     files ldap
> >> > shadow:     files ldap
> >> > group:      files ldap
> >> >
> >> > and remove the NOTFOUND entries
> >>
> >> Yes, done.
> >> Without networking, still the login failure trouble.
> >>
> >> With networking, no trouble at all, but with those timeouts of 30
> >> seconds and without those changes to nsswitch.conf, it takes a while
> >> for the first root login to succeed even though it is using local auth.
> > ----
> > do you have this line in /etc/pam.d/system-auth
> >
> > account     sufficient    pam_localuser.so
> >
> > ???
> >
> > What does your /etc/pam.d/system-auth look like?
> my /etc/pam.d/system-auth:
> #%PAM-1.0
> # This file is auto-generated.
> # User changes will be destroyed the next time authconfig is run.
> auth        required      pam_env.so
> auth        sufficient    pam_unix.so nullok try_first_pass
> auth        requisite     pam_succeed_if.so uid >= 500 quiet
> auth        sufficient    pam_ldap.so use_first_pass debug
> auth        required      pam_deny.so
> 
> account     required      pam_unix.so broken_shadow
> account     sufficient    pam_succeed_if.so uid < 500 quiet
> account     [default=bad success=ok user_unknown=ignore] pam_ldap.so
> account     required      pam_permit.so
> 
> password    requisite     pam_cracklib.so try_first_pass retry=3
> password    sufficient    pam_unix.so md5 shadow nullok try_first_pass  
> use_authtok
> password    sufficient    pam_ldap.so use_authtok debug
> password    required      pam_deny.so
> 
> session     optional      pam_keyinit.so revoke
> session     required      pam_limits.so
> session     [success=1 default=ignore] pam_succeed_if.so service in  
> crond quiet use_uid
> session     required      pam_unix.so
> session     optional      pam_ldap.so debug
> session     required      pam_mkhomedir.so skel=/etc/skel umask=0022
> 
> 
> ===
> I added
> 
> account     sufficient    pam_localuser.so
> 
> right before pam_ldap in the account section and tried again with the  
> same procedure (turn off networking (chkconfig --levels 2345 network  
> off), reboot).
> 
> Same result, login dies and gets restarted.
> 
> login: root
> Password:
> 
> login:
----
well, it hardly makes any sense to use ldap for user accounts and start
up with networking off but I would recommend that you adhere to the
advice at the top of the file and run 'authconfig' or
'system-config-authentication', make sure the settings are correct
(including checking the box for local authentication is sufficient) so
that it configures not only /etc/pam.d/system-auth and nsswitch.conf

Craig



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