Mongodb错误处理

MongoDB shell version: 3.0.6
connecting to: test
Server has startup warnings: 
2017-01-26T17:25:54.657+0800 I CONTROL  [initandlisten] 
2017-01-26T17:25:54.657+0800 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000　　

通过终端ulimit -a显示，指的是 -n openfile选项

$mongoimport --db test --collection restaurants --drop --file ~/downloads/primer-dataset.json
2017-01-26T17:27:11.882+0800	[........................] test.restaurants	0.0 B/11.3 MB (0.0%)
2017-01-26T17:27:12.409+0800	Failed: error connecting to db server: no reachable servers
2017-01-26T17:27:12.409+0800	imported 0 documents

$ mongorestore dump --host=127.0.0.1
2017-01-26T17:27:42.124+0800	building a list of dbs and collections to restore from dump dir
2017-01-26T17:27:42.125+0800	Failed: error scanning filesystem: error reading root dump folder: open dump: no such file or directory

$ mongoimport --host=127.0.0.1 --db test --collection restaurants --drop --file ~/downloads/primer-dataset.json
2017-01-26T17:32:44.206+0800	connected to: 127.0.0.1
2017-01-26T17:32:44.207+0800	dropping: test.restaurants
2017-01-26T17:32:45.572+0800	imported 25359 documents

百思不得其解，按照官网代码敲出来的，不过没用。加上--host=127.0.0.1来让mongodb知道host是本机。网上说3.0.7以后不会有这个问题，但显然我遇到了。