I am trying to setup Kerberos authentication to work with MongoDB Enterprise 4.4.
My OS is Centos 8.
I have configured SELinux as described in https://docs.mongodb.com/manual/tutorial/install-mongodb-enterprise-on-red-hat/.

In summary, I have no problem starting the mongod service if I follow the example shown by MongoDB docs (https://docs.mongodb.com/manual/tutorial/control-access-to-mongodb-with-kerberos-authentication/):

env KRB5_KTNAME=/data/mongodb/mongodb-svr.keytab \
mongod --tls --port 29000 --dbpath /data/mongodb --setParameter authenticationMechanisms=GSSAPI

(My instance has TLS activated and it's running using a custom port)

But once trying to start the service using systemctl, it just didn't want to run.

What I want to achieve is to successfully use systemctl to stop/start the mongod service.

In essence, my /etc/mongod.conf is as follows:

  authorization: enabled
    servers: myldap.mydomain.com:636
      queryUser: [email protected]
      queryPassword: somepassword
    transportSecurity: tls
  authenticationMechanisms: "PLAIN,SCRAM-SHA-256,MONGODB-X509"

The Setup
What I have for setup:

  1. I'm using Active Directory (Windows Server 2019) and Centos 8.

  2. I have configured the LDAP so it's accepting TLS/SSL (also have tested that everything works using LDAPAdmin.exe tool from another Windows machine).

  3. No issue running kinit or klist from the MongoDB machine.

  4. I have successfully integrated LDAP authentication with MongoDB before this (using simple option for bind).

  5. I have no issue authenticating to the MongoDB instance as one of domain users using LDAP integration (by configuring the userToDNMapping and authz.queryTemplate parameters).

  6. Custom MongoDB port: tcp/29000

  7. Custom MongoDB data path: /data/mongodb

  8. The CentOS 8 machine has already joined the domain (using realm join).

Configuration So Far
Now, I have tried to do the following for making Kerberos work:

  1. Created a Managed Service Account (svc_mongodb) on AD.

  2. Created the SPN as follows:

setspn -S mongodb/mongodb-svr.mydomain.com:[email protected] svc_mongodb
  1. Created the keytab file using ktpass:
ktpass /out mongodb-svr.keytab /princ mongodb/mongodb-svr.mydomain.com:[email protected] /mapuser svc_mongod /crypto AES256-SHA1 /ptype KRB5_NT_PRINCIPAL /pass somepassword
  1. Put the keytab on /data/mongodb/mongodb-svr.keytab (on the CentOS machine). Also chown and chmod it to mongod user and 400.

  2. Start the mongod service with the command line (this works):

env KRB5_KTNAME=/data/mongodb/mongodb-svr.keytab \
mongod --tls --port 29000 --dbpath /data/mongodb --setParameter authenticationMechanisms=GSSAPI

What Failed
However, when I change the /etc/mongod.conf to this:

  authenticationMechanisms: "GSSAPI,SCRAM-SHA-256,MONGODB-X509"

I got this error: Unspecified GSS failure. Minor code may provide more information; Minor code 13; Permission denied

Looking at the audit log, I noticed this:

type=AVC msg=audit(1624773960.885:206): avc:  denied  { open } for  pid=2771 comm="mongod" path="/etc/krb5.keytab" dev="dm-0" ino=8388741 scontext=system_u:system_r:mongod_t:s0 tcontext=system_u:object_r:krb5_keytab_t:s0 tclass=file permissive=0

Okay, that's expected since I haven't configured the SELinux file context so that mongod can open it. But I don't want to if possible, because I want to use the specific keytab file instead.

What I Have Tried

  1. I tried to follow https://docs.mongodb.com/manual/tutorial/control-access-to-mongodb-with-kerberos-authentication/#std-label-setting-krb5_ktname by editing /etc/sysconfig/mongod on my Centos 8.

  2. I tried to edit the systemctl service file (/usr/lib/systemd/system/mongod.service) to add this line: (afterwards run systemctl daemon-reload).

ExecStartPre=/usr/bin/env KRB5_KTNAME=/data/mongodb/mongodb-svr.keytab
  1. Created a .profile under the mongod's home directory and export the KRB5_KTNAME variable there.

  2. Created a krb.sh under the /etc/profile.d directory and export the KRB5_KTNAME variable there.

None of the above worked so far.
So I'm confused as to why (and how exactly can I set this variable).
I really want to avoid having to setfacl -m the /etc/krb5.keytab file, or having to create additional SELinux policy (should be easily done via audit2allow).

If anyone could point my mistakes, that'd be of great help.

1 Answer 1


When you run

mongod --tls --port 29000 --dbpath /data/mongodb --setParameter authenticationMechanisms=GSSAPI

then mongod does not read the config file /etc/mongod.conf. I suggest not mixing command-line parameters and configuration file. Put all parameters into your config file /etc/mongod.conf and start your mongod with

mongod -f /etc/mongod.conf

The command line options seem to take precedence, so --setParameter authenticationMechanisms=GSSAPI overwrites your authenticationMechanisms: "GSSAPI,SCRAM-SHA-256,MONGODB-X509" in the /etc/mongod.conf file.

  • Thanks! Although not directly, your answer actually pointed me towards the right direction. It's solved now. Appreciate your help.
    – Adley F
    Jun 29, 2021 at 10:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.