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The nslookup command is originally a DNS server testing tool. Linux and Solaris versions of nslookup will always try to contact a DNS server, because that's what it's programmed to do.
HP-UX nslookup does not behave like Linux or Solaris nslookup. It behaves more like Solaris getent Command. So it does not consult DNS only like "normal" nslookup. It checks all sources in the order specified in /etc/nsswitch.conf
In HP-UX /etc/nsswitch.conf file there is elaborate (aka over-engineered) set of criteria for continuation of search and it looks like on some of our boxes they are set sub-optimally.
For example:
cat /etc/nsswitch.conf
hosts: files[NOTFOUND=continue UNAVAIL=continue TRYAGAIN=continue] \
dns[NOTFOUND=return UNAVAIL=continue TRYAGAIN=return]
Should probably be
hosts: files[SUCCESS=return NOTFOUND=continue UNAVAIL=continue TRYAGAIN=continue] \
dns[NOTFOUND=return UNAVAIL=continue TRYAGAIN=return]
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One side effect of the first configuration (without SUCCESS=return) is that even if the entry exists, HP-UX in its infinite wisdom continue looking in DNS and use DNS resolution of it. Which might make sense in some cases, but in most cases, like was the case with nti244, it does not and it makes it impossible to override DNS resolution with the entry in /etc/hosts file. Which is not what sysadmins who get used to Linux and Solaris expect.
Here is the meaning of HP /etc/nsswitch.conf keywords:
- SUCCESS
Requested database entry was found
- UNAVAIL
Source is not responding or corrupted
- NOTFOUND
Source responded "no such entry"
- TRYAGAIN
Source is busy, might respond to retries
For each status code, two actions are possible:
- Action
Meaning
- continue
Try the next source in the list
- return
Return now
The complete syntax of an entry is
<entry> ::= <database> ":" [<source> [<criteria>]]* <source> <criteria> ::= "[" <criterion>+ "]" <criterion> ::= <status> "=" <action> <status> ::= "success" | "notfound" | "unavail" | "tryagain" <action> ::= "return" | "continue"Each entry occupies a single line in the file. Lines that are blank, or that start with white space character are ignored. Everything on a line following a # character is also ignored; the # character can begin anywhere in a line, to be used to begin comments. The database and source names are case-sensitive, but action and status names are case-insensitive.
The default criteria are to continue on anything except SUCCESS; in other words, [SUCCESS=return NOTFOUND=continue UNAVAIL=continue TRYAGAIN=continue].
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