package slapd 2.4.21-0ubuntu5.2 failed to install/upgrade

Thank you for taking the time to report this bug and helping to make Ubuntu better.

According to the logs:

Configurando slapd (2.4.21-0ubuntu5.2) ...
  Backing up /etc/ldap/slapd.d/ in /var/backups/slapd-2.4.21-0ubuntu5... done.
  Enabling LDAPv2 support... Starting OpenLDAP: slapd - failed.
The operation failed but no output was produced. For hints on what went
wrong please refer to the system's logfiles (e.g. /var/log/syslog) or
try running the daemon in Debug mode like via "slapd -d 16383" (warning:
this will create copious output).

Below, you can find the command line options used by this script to
run slapd. Do not forget to specify those options if you
want to look to debugging output:
  slapd -h 'ldap:/// ldapi:///' -g openldap -u openldap -F /etc/ldap/slapd.d/
invoke-rc.d: initscript slapd, action "start" failed.

Could you look at the /var/log/syslog file to figure out what may have gone wrong?
Could you run the following command as root to figure out why slapd is failing to start:

 slapd -h 'ldap:/// ldapi:///' -g openldap -u openldap -F /etc/ldap/slapd.d/ -d 16383

Output you asked for:

sudo slapd -h 'ldap:/// ldapi:///' -g openldap -u openldap -F /etc/ldap/slapd.d/ -d 16383
@(#) $OpenLDAP: slapd 2.4.21 (Jul 30 2010 01:09:23) $
 buildd@rothera:/build/buildd/openldap-2.4.21/debian/build/servers/slapd
ldap_pvt_gethostbyname_a: host=fanna, r=0
daemon_init: ldap:/// ldapi:///
daemon_init: listen on ldap:///
daemon_init: listen on ldapi:///
daemon_init: 2 listeners to open...
ldap_url_parse_ext(ldap:///)
daemon: listener initialized ldap:///
ldap_url_parse_ext(ldapi:///)
daemon: bind(9) failed errno=2 (No such file or directory)
slap_open_listener: failed on ldapi:///
slapd stopped.
connections_destroy: nothing to destroy.

After executing it, syslog appears to have exactly the same information, so it would be quite redundant. If you need it, ask again.

I can't find right now what were the syslog entries when trying to install. It was some time ago.

Thank you for your time.

> sudo slapd -h 'ldap:/// ldapi:///' -g openldap -u openldap -F /etc/ldap/slapd.d/ -d 16383
> @(#) $OpenLDAP: slapd 2.4.21 (Jul 30 2010 01:09:23) $
> buildd@rothera:/build/buildd/openldap-2.4.21/debian/build/servers/slapd
> ldap_pvt_gethostbyname_a: host=fanna, r=0
> daemon_init: ldap:/// ldapi:///
> daemon_init: listen on ldap:///
> daemon_init: listen on ldapi:///
> daemon_init: 2 listeners to open...
> ldap_url_parse_ext(ldap:///)
> daemon: listener initialized ldap:///
> ldap_url_parse_ext(ldapi:///)
> daemon: bind(9) failed errno=2 (No such file or directory)

Here is the error. We should try to find out which file slapd is trying
to open.

Could you strace the process to figure out which directory or file slapd
is trying to open for ldapi?

  sudo strace slapd -h 'ldap:/// ldapi:///' -g openldap -u openldap -F /etc/ldap/slapd.d/ -d 16383

I supposed it was a bad configuration file, but I didn't find anything wrong (although I'm not very skilled with openldap). And I have not touched it in years.

Here you have the strace slapd output, as asked.

Looking at the strace, it seems that slapd fails with a different error now:

config error processing olcDatabase={-1}frontend,cn=config: ordered_value_sort failed on attr olcAccess

This is bug 571057.