Hi,All
With openldap 2.4.x which supports memberOf overlay. I can get group info with only one search with following configs.
<1>
[root@/jacky/var]$cat user.ldif
  dn: cn=jacky,ou=users,dc=jacky,dc=com
  objectClass: organizationalPerson
  cn: jacky
  sn: sun
  userPassword: 11111111
 
[root@/jacky/var]$cat JackyGroup.ldif
dn: cn=JackyGroup,ou=groups,dc=jacky,dc=com
objectClass: groupOfNames
cn: JackyGroup
member: cn=jacky,ou=users,dc=jacky,dc=com
 
<2>
memberOf overlay is configured correctly
 
<3>
[root@/jacky/var]$ldapsearch -x -D "cn=root,dc=jacky,dc=com" -b "dc=jacky,dc=com" -H "ldap://x.x.x.x:389" -w xxx -s sub "(cn=jacky)" memberOf
# extended LDIF
#
# LDAPv3
# base <dc=jacky,dc=com> with scope subtree
# filter: (cn=jacky)
# requesting: memberOf
#
# jacky, users, jacky.com
dn: cn=jacky,ou=users,dc=jacky,dc=com
memberOf: cn=JackyGroup,ou=groups,dc=jacky,dc=com       [This is what I want]
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1

My questions are here:
A1: With openldap 2.4.x, if posixAccount is used to manage users, then attribute 'gidNumber' which is a number will represent user's membership.
With this case, is it possible that I can get group info(DN format as above) of a user entry by ONLY one search?
 
A2: With older openldap whihc does NOT support memberOf overlay:
    <1> If organizationalPerson is used to manage users, is it possible that I can get group info(DN format) of a user entry by ONLY one search?
    <2> If posixAccount is used to manage users, is it possible that I can get group info(DN format) of a user entry by ONLY one search?Any reply is appreciated~TIA
   
Thanks,
Jacky