There is an issue with RHEL9 starting the mongod deamon with systemctl start mongod.

Two examples of this issue are:

1. Moving the database location
2. Changing Listing port

Example 1. Database location
storage:
dbPath: /var/lib/mongo

network interfaces

net:
port: 27017

systemctl start mongod – this works just fine as the defaults.

Now lets move the DB directory to \var\lib\mongo1 – SAME mount point, SAME permissions

[root@REDHAT-3212 firewalld]# ll /var/lib | grep mongo
drwxr-xr-x. 5 mongod mongod 4096 Apr 17 15:27 mongo
drwxr-xr-x. 2 mongod mongod 6 Apr 17 15:27 mongo1

storage:
dbPath: /var/lib/mongo1
systemctl start mongod –

FAILS with permission issue:

{“t”:{“$date”:“2024-04-17T15:30:16.960-05:00”},“s”:“E”, “c”:“WT”, “id”:22435, “ctx”:“initandlisten”,“msg”:“WiredTiger error message”,“attr”:{“error”:13,“message”:“[1713385816
:960404][159449:0x7f26d62a0b80], wiredtiger_open: [WT_VERB_DEFAULT][ERROR]: __posix_open_file, 815: /var/lib/mongo1/WiredTiger.lock: handle-open: open: Permission denied”}}

BUT – what if we SU to mongod and run it:
su mongod -c “mongod -f /etc/mongod.conf”

It WORKS just fine – Mongo daemon starts up just fine.
Its only an issuer when starting from systemctl

Example 2. Database port — lets change the port
storage:
dbPath: /var/lib/mongo

network interfaces

net:
port: 26019

When we start with systemctl it FAILS with BIND issue
systemctl start mongod –

{“t”:{“$date”:“2024-04-17T15:35:44.571-05:00”},“s”:“E”, “c”:“CONTROL”, “id”:20568,
“ctx”:“initandlisten”,“msg”:“Error setting up listener”,“attr”:{“error”:{“code”:9001,“codeName”:
“SocketException”,“errmsg”:“setup bind :: caused by :: Permission denied”}}}

But lets start it with SU
su mongod -c “mongod -f /etc/mongod.conf”

{“t”:{“$date”:“2024-04-17T15:36:52.742-05:00”},“s”:“I”, “c”:“NETWORK”, “id”:23016, “ctx”:“listener”,“msg”:“Waiting for connections”,“attr”:{“port”:26019,“ssl”:“off”}}
IT WORKS just fine

Why do we get permission issues with starting with systemctl – as a service it should start as mongod

When starting it with normal parameters we see the daemon running under mongod.
mongod 159959 1 29 15:38 ? 00:00:00 /usr/bin/mongod -f /etc/mongod.conf

I cannot do a ls on the file because it is not created - this is a new directory that is empty.

This is installed on a RHEL9 server using the following as it pulls it from the latest repo.
There was nothing creating by hand, everything was done via the install - and yes, I
agree mongod vs mongodb is a bit weird – seems it install differently on different systems.

yum install -y mongodb-org

thanks

ok- I am not clear what the unit file you are requesting I post.
which file is this?
thanks

found it - here it is

cat mongod.service

[Unit]
Description=MongoDB Database Server
Documentation=https://docs.mongodb.org/manual
After=network-online.target
Wants=network-online.target

[Service]
User=mongod
Group=mongod
Environment=“OPTIONS=-f /etc/mongod.conf”
Environment=“MONGODB_CONFIG_OVERRIDE_NOFORK=1”
EnvironmentFile=-/etc/sysconfig/mongod
ExecStart=/usr/bin/mongod $OPTIONS
RuntimeDirectory=mongodb

file size

LimitFSIZE=infinity

cpu time

LimitCPU=infinity

virtual memory size

LimitAS=infinity

open files

LimitNOFILE=64000

processes/threads

LimitNPROC=64000

locked memory

LimitMEMLOCK=infinity

total threads (user+kernel)

TasksMax=infinity
TasksAccounting=false

Recommended limits for mongod as specified in

https://docs.mongodb.com/manual/reference/ulimit/#recommended-ulimit-settings

[Install]
WantedBy=multi-user.target

Yes, it is SELINUX which is the culprit .

I found this: https://www.mongodb.com/docs/manual/tutorial/install-mongodb-on-red-hat/
Which states:
###################################################
If your MongoDB deployment uses custom settings for any of the following:

• [MongoDB connection ports

• [dbPath

You cannot use the MongoDB supplied SELinux policy. An alternative is to create a [custom SELinux policy]

###############################################

It gives instructions on how to build a new policy

1. Download the policy repository.

git clone htps://github.com/mongodb/mongodb-selinux

2. Build the policy.
   cd mongodb-selinuxmake
   3. Apply the policy.
   sudo make install

However, even doing that does not fix the issue.
Even checking that the new policy is added for the new folder (/data/mongo)

/data/mongo(/.*)?                              all files          system_u:object_r:mongod_var_lib_t:s0
/data/mongo.*                                      all files          system_u:object_r:mongod_var_lib_t:s0
/run/mongodb(/.*)?                                 all files          system_u:object_r:mongod_runtime_t:s0
/usr/bin/mongod                                    regular file       system_u:object_r:mongod_exec_t:s0
/var/lib/mongo(/.*)?                               all files          system_u:object_r:mongod_var_lib_t:s0
/var/log/mongodb(/.*)?                             all files          system_u:object_r:mongod_log_t:s0

We still get permissioned denied when starting up with systemctl.

It is irritating that its documented that it needs a fix, provides a fix, yet still does not work.

I can of course turn off SELINUX but not sure that is the best solution.

Thanks for the help