Tips: solution for [warning: dict_nis_init: NIS domain name not set - NIS lookups disabled]

error messages in maillog:


May 24 23:24:03 TXB-FW postfix/smtpd[31444]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
May 24 23:24:03 TXB-FW postfix/smtpd[31444]: warning: SASL: Connect to private/auth failed: Connection refused
May 24 23:24:03 TXB-FW postfix/smtpd[31444]: fatal: no SASL authentication mechanisms

First of I didn't ask postfix to do NIS lookups.

The fix was simple.

alias_maps when commented, uses the default settings:
alias_maps = hash:/etc/aliases, nis:mail.aliases

This allows postfix to work even without explicit alias_maps settings. However the default also encumbers it with checking nis. Setting alias_maps explicitly eliminates the problem:
alias_maps = hash:/etc/aliases

http://blog.taragana.com/index.php/archive/how-to-fix-postfix-warning-dict_nis_init-nis-domain-name-not-set-nis-lookups-disabled/

free command information explanation

# free

total used free shared buffers cached
Mem: 1021452 90948 930504 0 5320 61128
-/+ buffers/cache: 24500 996952
Swap: 2104472 0 2104472


total - size of the total memory 1021452Bytes
used - memory that has been used 90948Bytes
free - memory that hasn't been used 930504Bytes
shared - abandoned currently is always 0
buffers - buffer memory 5320Bytes
cache - cache memory 61128Bytes

The relationship:

total = used + free

(- /buffers/cache) used memory: used memory=used-buffers-cached
(+/buffers/cache) free memory: free memory=free + buffers + cached

-/buffers/cache reflects the size of memory that the programe really have used , and +/buffers/cache reflect the total size of memory that can be misappropriated.