Linux, if there is a problem, then the best way to row is to view the log, but for performance, some applications, the lack of savings did not open the error log, we need to enable.
APACHE
# tail&http://www.aliyun.com/zixun/aggregation/37954.html ' >nbsp; /var/log/apache2/error.log #查看log
# Tail-0f/var/log/apache2/error.log #实时查看log
OPENLDAP
When you use LDAP to authenticate users, and when a user logs on to a problem, you need to look at the LDAP log and see where the error occurs.
By default, OpenLDAP log is not enabled and we need to modify the configuration file/etc/ldap/slapd.conf
LogLevel 256 # <--Change form 0 to 256
Restarting the LDAP Service
/ETC/INIT.D/SLAPD restart
View Log
Tail/var/log/openldap.log
Dovecot
When there is a problem receiving mail, we need to check dovecot log,
Edit/etc/dovecot/dovecot.conf
Mail_debug = yes #把注释去掉
Restart the Dovecot service
#/etc/init.d/dovecot Restart
View Log
# Tail/var/log/dovecot.log