One problem description
mongo起不来，日志里有如下报错：
2020-12-29T09:31:29.933+0800 W - [initandlisten] Detected unclean shutdown - /var/lib/mongo/mongod.lock is not empty.
2020-12-29T09:31:29.933+0800 E NETWORK [initandlisten] Failed to unlink socket file /tmp/mongodb-27017.sock Operation not permitted
2020-12-29T09:31:29.933+0800 F - [initandlisten] Fatal Assertion 40486 at src/mongo/transport/transport_layer_asio.cpp 170
Two reasons for the error
Mongo is not shut down normally, the command to shut down mongo normally:
use admin
db.shutdownServer()
Three solutions
Delete the lock file, repair the database, and then start mongo.
mv mongod.lock mongod.lock_bak_20201229
mongod --repair --dbpath / var / lib / mongo
chown -R mongod:mongod /var/lib/mongo #mongod is the owner of /var/lib/mongo. Please modify the user name according to your actual situation. If the owner is root, you do not need to perform this operation.
/usr/bin/mongod -f /etc/mongod.conf