How to get rid of "Could not connect to database" with Linux and libnss-pgsql2?

I use libnss-pgsql2 in order to have virtual system users stored in a PostgreSQL database. The virtual users in the database work just fine. They can log in. I can see their uid, gid, groups via the 'id' command. Example:

# id backup001
uid=10001(backup001) gid=10001(backup001) groups=10001(backup001)

However, on systems that I use libnss, I frequently get this error:

Could not connect to database

It happens, for instance, often with cron-jobs. I have one cron-job that runs every hour that dumps the postgresql databases to a backup. The contrab is this:

04 *  *   *   *     postgres umask 077 && /usr/bin/pg_dumpall | gzip > ~postgres/backup/postgresql-complete-dump-$(date +\%H).sql.gz

This job always produces the error. Thus, flooding me with an e-mail every hour.

My setup is pretty simple: The table layout I use to store the users is available here: http://p.adora.dk/P2486.html

I use Debian Squeeze on the server.

Relevant config files are: nsswitch.conf : http://p.adora.dk/P2489.html

(description: use "normal" system users in /etc/passwd and /etc/shadow, however, if the user is NOT found, then proceed with a lookup via pgsql)

nss-pgsql.conf : http://p.adora.dk/P2487.html

(description: contains the SQL queries that are used to look up various information that normally is found in /etc/passwd and /etc/group)

nss-pgsql-root.conf : http://p.adora.dk/P2488.html

(description: contains the SQL queries that are used to lookup confidential info that is normally found in /etc/shadow)

Things that I have done to debug this:

• Verified that the connection strings in both nss-pgsql.conf and nss-pgsql-root.conf work as intended.
• Verified that the timeout does not occur. I.e. the error is echoed immediately and not after 300 seconds. Also, this happens on a server that does not do anything - so the connection should be established without delay -- I have verified that it does.

I really hope you can help me fix this error.

Update 2012-08-22:

I tried doing an strace on psql. The relevant part of the strace is in the bottom of this paste: http://paste.adora.dk/P2492.html

I notice that it tries opening /etc/nss-pgsql-root.conf and get EACCESS, however, I do not believe this should be a problem. This file should be readable by root only as it corresponds to /etc/shadow which is also only readable by root.

25341 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
25341 open("/usr/lib/libgpg-error.so.0", O_RDONLY) = 4
25341 read(4, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 \6\0\0004\0\0\0"..., 512) = 512
25341 fstat64(4, {st_mode=S_IFREG|0644, st_size=11540, ...}) = 0
25341 mmap2(NULL, 14512, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0xb6f6c000
25341 mmap2(0xb6f6f000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 4, 0x2) = 0xb6f6f000
25341 close(4)                          = 0
25341 mprotect(0xb70bf000, 4096, PROT_READ) = 0
25341 mprotect(0xb73d8000, 4096, PROT_READ) = 0
25341 munmap(0xb7414000, 40018)         = 0
25341 open("/etc/nss-pgsql-root.conf", O_RDONLY) = -1 EACCES (Permission denied)
25341 write(2, "\nCould not connect to database\n", 31) = 31

It is possible that this is a bug in libnss-pgsql.... What do you think?

Update 2012-08-22:

OK. I dug up this five year old bug report: http://pgfoundry.org/tracker/index.php?func=detail&aid=1010197&group_id=1000039&atid=234

It seems that this behavior is actually a bug. A patch has been provided, however, there is no activity on the bug report. Maybe the project is abandoned. I certainly hope not :(