MongoDB service won't start after moving location (Centos 7.1.1503) - mongodb

Question

Previously mongodb was located at /var/lib/mongod. I've moved this to /home/mongod, and updated the /etc/mongod.conf file to point to this location. The permissions of the folder look correct:
drwxrwxr-x. 2 mongod mongod 6 Aug 6 10:37 admin
-rw-------. 1 mongod mongod 67108864 Aug 6 11:49 admin.0
-rw-------. 1 mongod mongod 16777216 Aug 6 11:49 admin.ns
drwxrwxr-x. 2 mongod mongod 6 Aug 6 10:40 journal
drwxrwxr-x. 2 mongod mongod 6 Aug 6 10:37 local
-rw-------. 1 mongod mongod 67108864 Aug 6 11:49 local.0
-rw-------. 1 mongod mongod 16777216 Aug 6 11:49 local.ns
-rwxr-xr-x. 1 mongod mongod 0 Aug 6 11:50 mongod.lock
-rwxrwxr-x. 1 mongod mongod 0 Aug 6 10:12 mongod.lock.bak
drwxrwxr-x. 2 mongod mongod 6 Aug 6 10:37 sphere
-rw-------. 1 mongod mongod 67108864 Aug 6 11:50 sphere.0
-rw-------. 1 mongod mongod 134217728 Aug 6 11:49 sphere.1
-rw-------. 1 mongod mongod 268435456 Aug 6 11:49 sphere.2
-rw-------. 1 mongod mongod 536870912 Aug 6 11:49 sphere.3
-rw-------. 1 mongod mongod 1073741824 Aug 6 11:50 sphere.4
-rw-------. 1 mongod mongod 2146435072 Aug 6 11:50 sphere.5
-rw-------. 1 mongod mongod 16777216 Aug 6 11:50 sphere.ns
drwxr-xr-x. 2 mongod mongod 6 Aug 6 11:50 _tmp
and when I run from the command line it works:
[user#localhost home]$ sudo -u mongod mongod --dbpath /home/mongod
[sudo] password for user:
2015-08-06T12:04:35.761+0100 [initandlisten] MongoDB starting : pid=10235 port=27017 dbpath=/home/mongod 64-bit host=localhost.localdomain
2015-08-06T12:04:35.762+0100 [initandlisten] db version v2.6.10
2015-08-06T12:04:35.762+0100 [initandlisten] git version: 5901dbfb49d16eaef6f2c2c50fba534d23ac7f6c
2015-08-06T12:04:35.762+0100 [initandlisten] build info: Linux build18.nj1.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
2015-08-06T12:04:35.762+0100 [initandlisten] allocator: tcmalloc
2015-08-06T12:04:35.762+0100 [initandlisten] options: { storage: { dbPath: "/home/mongod" } }
2015-08-06T12:04:35.772+0100 [initandlisten] journal dir=/home/mongod/journal
2015-08-06T12:04:35.773+0100 [initandlisten] recover : no journal files present, no recovery needed
2015-08-06T12:04:36.865+0100 [initandlisten] waiting for connections on port 27017
However running the using systemctl fails:
sudo service mongod restart
Restarting mongod (via systemctl): Job for mongod.service failed. See 'systemctl status mongod.service' and 'journalctl -xn' for details.
[FAILED]
The /etc/mongod.conf file is as follows
logpath=/var/log/mongodb/mongod.log
logappend=true
# fork and run in background
fork=true
#port=27017
dbpath=/home/mongod
# location of pidfile
pidfilepath=/var/run/mongodb/mongod.pid
# Listen to local interface only. Comment out to listen on all interfaces.
bind_ip=127.0.0.1
The output in /var/log/mongod/mongod.log is as follows:
2015-08-06T12:08:35.402+0100 ***** SERVER RESTARTED *****
2015-08-06T12:08:35.407+0100 [initandlisten] MongoDB starting : pid=10370 port=27017 dbpath=/home/mongod 64-bit host=localhost.localdomain
2015-08-06T12:08:35.407+0100 [initandlisten] db version v2.6.10
2015-08-06T12:08:35.407+0100 [initandlisten] git version: 5901dbfb49d16eaef6f2c2c50fba534d23ac7f6c
2015-08-06T12:08:35.407+0100 [initandlisten] build info: Linux build18.nj1.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
2015-08-06T12:08:35.407+0100 [initandlisten] allocator: tcmalloc
2015-08-06T12:08:35.407+0100 [initandlisten] options: { config: "/etc/mongod.conf", net: { bindIp: "127.0.0.1" }, processManagement: { fork: true, pidFilePath: "/var/run/mongodb/mongod.pid" }, storage: { dbPath: "/home/mongod" }, systemLog: { destination: "file", logAppend: true, path: "/var/log/mongodb/mongod.log" } }
2015-08-06T12:08:35.407+0100 [initandlisten] exception in initAndListen std::exception: boost::filesystem::status: Permission denied: "/home/mongod/local.ns", terminating
2015-08-06T12:08:35.407+0100 [initandlisten] dbexit:
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: going to close listening sockets...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: going to flush diaglog...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: going to close sockets...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: waiting for fs preallocator...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: lock for final commit...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: final commit...
2015-08-06T12:08:35.407+0100 [initandlisten] shutdown: closing all files...
2015-08-06T12:08:35.407+0100 [initandlisten] closeAllFiles() finished
2015-08-06T12:08:35.407+0100 [initandlisten] dbexit: really exiting now
I've tried deleting the lock file /home/mongod/mongod.lock and running a repair with sudo -u mongod mongod --dbpath /home/mongod --repair but the error still persists. This is causing major headaches!!

Answer 1

So it turns out the problem was SElinux, and the solution is the same as this question.
It was permission related and is due to the SELinux security context which is set to enforced by default on CentOS.
sudo ausearch -m avc -ts today | audit2allow
On my machine I had some mongo related audits as follows:
#============= mongod_t ==============
allow mongod_t home_root_t:file getattr;
allow mongod_t user_home_dir_t:dir search;
allow mongod_t var_lib_t:lnk_file read;
allow mongod_t default_t:file getattr;
To fix the above, you do the following:
sudo chcon -Rv --type=mongod_var_lib_t /path_to_your_mongo
Where /path_to_your_mongo is where your mongod data files are located (in my case /home/mongod but often /var/lib/mongo or /data/db.