This is an upgrade from 4.1 to 4.2. On all our servers the "nc" binary is provided by the "netcat-traditional" package. The package "netcat-openbsd" is not installed.

In such a setup the join script hangs in the following line:

if ! nc -w 10 "$ldap_master" "${ldap_master_port:-7389}"; then

The reason is that both netcat variants handle the "-w 10" parameter slightly differently. For netcat-openbsd, the timer starts to run as soon as the program starts. For netcat-traditional, however, the timer starts to run as soon as nc cannot read any input anymore. As input is read from STDIN, this hangs until the user presses Ctrl+D. Ten seconds later nc from netcat-traditional will exit, too.

Meaning one can use "Ctrl+D" in order to continue a seemingly hanging execution of "33univention-portal.inst".

One possible workaround is to redirect nc's STDIN from /dev/null. Unfortunately nc.traditional still hangs for 10 seconds, even with STDIN being redirected.

Here are two tests with "STDIN < /dev/null", one for each nc variant, once with a reachable port (7389), once with an unreachable one (7388):

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[0 root@master ~] date ; nc.openbsd -w 10 master.mbu-test.intranet 7388 < /dev/null ; echo $? ; date
Mo 15. Mai 15:46:39 CEST 2017
1
Mo 15. Mai 15:46:39 CEST 2017
[0 root@master ~] date ; nc.openbsd -w 10 master.mbu-test.intranet 7389 < /dev/null ; echo $? ; date
Mo 15. Mai 15:46:43 CEST 2017
0
Mo 15. Mai 15:46:43 CEST 2017
[0 root@master ~] date ; nc.traditional -w 10 master.mbu-test.intranet 7388 < /dev/null ; echo $? ; date
Mo 15. Mai 15:46:50 CEST 2017
master.mbu-test.intranet [10.191.1.1] 7388 (?) : Connection refused
1
Mo 15. Mai 15:46:50 CEST 2017
[0 root@master ~] date ; nc.traditional -w 10 master.mbu-test.intranet 7389 < /dev/null ; echo $? ; date
Mo 15. Mai 15:46:57 CEST 2017
0
Mo 15. Mai 15:47:17 CEST 2017
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The proper solution would be to make one of Univention's common packages (e.g. "univention-server-common") depend on netcat-openbsd, and to call "nc.openbsd" in the join script. Calling "nc" will still call "/etc/alternatives/nc" which a join script (or any other script) cannot rely on being anything in particular.

Other scripts use "nc", too, and should be checked as well:

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[0 root@master ~] grep -Pr '\bnc\b' /usr/lib/univention-install
/usr/lib/univention-install/33univention-portal.inst:if ! nc -w 10 "$ldap_master" "${ldap_master_port:-7389}"; then
/usr/lib/univention-install/15univention-directory-notifier-post.inst:          nc -z localhost 6669 && break
[0 root@master ~]
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