getgrouplist() has different return values on Linux and FreeBSD:
Linux: either the number of groups (positive) or -1 on error
FreeBSD: 0 on success or -1 on error
The return value of getgrouplist() is analyzed in Linux-specific way in
hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/security/hadoop_user_info.c, in function hadoop_user_info_getgroups() which breaks FreeBSD.
In this function you have 3 choices for the return value
ret = getgrouplist(uinfo->pwd.pw_name, uinfo->pwd.pw_gid,
1) ret > 0 : OK for Linux, it will be zero on FreeBSD. I propose to change this to ret >= 0
2) First condition is false and ret != -1: impossible according to manpage
3) ret == 1 – OK for both Linux and FreeBSD
So I propose to change "ret > 0" to "ret >= 0" and (optionally) return 2nd case.