apt-get install gnupg

wget -qO - https://www.mongodb.org/static/pgp/server-6.0.asc | sudo apt-key add -

echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/6.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-6.0.list

apt-get update

apt-get install -y mongodb-org

/etc/mongod.conf

mongod -f /etc/mongod.conf --shutdown

db.getCollection("bolg").createIndex({"source":1,"date":-1});

> db.test.ensureIndex({"userid":1},{"unique":true,"dropDups":true}) 

> db.runCommand({"distinct":"table_name","key":"field_name"})

# 查看非重复值个数
> db.getCollection("table_name").distinct('field_name').length

# 找出指定字段重复数
> db.AI_online.aggregate([{$group : {_id : "$title", num : {$sum : 1}}},{$match :{num:{$gt : 1}}},{$sort:{num:-1}}])

# 删除指定字段重复值，只保留一个（去重）
> db.AI_online.aggregate([
{
    $group: { _id: {title: '$title'},count: {$sum: 1},dups: {$addToSet: '$_id'}}
},
{
    $match: {count: {$gt: 1}}
}
]).forEach(function(doc){
    doc.dups.shift();
    db.AI_online.remove({_id: {$in: doc.dups}});
})

db.test_info.find({"tname": {$regex: '测试', $options:'i'}}) 

db.test_info.find({"tname": {$regex:/测试.*/i}})

db.test_info.find({"$or":[{"title":{$regex:/测试.*/i}},{"summary":{$regex:/测试.*/i}}]}) 

rpm -ivh https://repo.mongodb.org/yum/redhat/7/mongodb-org/5.0/x86_64/RPMS/mongodb-org-server-5.0.6-1.el7.x86_64.rpm  --force --nodeps

wget -qO - https://www.mongodb.org/static/pgp/server-5.0.asc | sudo apt-key add -
echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/5.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-5.0.list
vim /etc/apt/sources.list.d/mongodb-org-5.0.list
apt update
apt-get install -y mongodb-org

systemctl start mongod
systemctl stop mongod

cat /proc/sys/fs/file-max     # file-max（系统级别）是设置系统所有进程一共可以打开的最大文件数量。
cat /etc/security/limits.conf # 永久配置文件（注意WSL2下这个值貌似没生效）
ulimit -n                     # 查看用户级的限制，阿里云服务器一般是65535
ulimit -a                     # 查看当前的各种用户进程限制
ulimit -SHn 65535             # 临时修改系统句柄限制，加-H就是硬限制，加-S就是软限制

apt remove mongodb-server-core

security:
  authorization: enabled

1、.lock文件不要拷贝；
2、diagnostic.data的文件夹不要拷贝，如果拷贝，在新的数据库运行时会出现错误，需要修复，时间有点长。

apt-get install mongodb
apt-get install mongodb-org

mongod -f /etc/mongodb.conf -fork   //使用配置文件启动，并后台执行

mongo --host xx.xx.xx.xx --port 123

use test
db.addUser("test","test")

// 方式一
mongo
use admin
db.auth('admin', '123456')

// 方式二
mongo admin -u admin -p 123456

db.createUser(
  { user: "admin",
    pwd: "admin",
    roles: [ { role: "root", db: "admin" } ]
  }
)

db.changeUserPassword("admin", "654321")

db.createUser(
  { user: "spider",
    pwd: "spider",
    roles: [ { role: "readWrite", db: "spider" } ]
  }
)

security:
    authorization: enabled