Mongodb 使用 brew upgrade Mongo update from 3.4 to 4.0 报错：在try 升级到 4.0 之前，数据文件需要完全升级到 3.6 版

我需要将MongoDB降级到3.4.清理所有版本.然后逐步升级到3.6和4.0.

First of all, back up your /data/db, just in case.

以下步骤是根据我的经验，我使用brew安装/卸载mongodb.

我遵循了这个线程中的指令，但在iMac上运行了以下步骤.

Error while upgrading Mongodb from 3.2 to 3.6

Uninstall your current mongodb

brew uninstall mongodb

Install mongodb 3.4 version

brew install mongodb@3.4

Start mongod 3.4 version(当你像上面那样安装旧版本时，你需要完整的路径来运行它.)

/usr/local/opt/mongodb@3.4/bin/mongod

Start mongo 3.4 version

/usr/local/opt/mongodb@3.4/bin/mongo

Run the important command

> db.adminCommand( { setFeatureCompatibilityVersion: "3.4" } )

Quit

>quit();

Terminate the mongod

Find PID of mongod process using $ top

Kill the process by $ kill <PID> (the Mongo docs have more info on this)

Uninstall mongodb 3.4

brew uninstall mongodb@3.4

对3.6重复上述步骤

Install mongodb 3.6 version

brew install mongodb@3.6

Start mongod 3.6 version

/usr/local/opt/mongodb@3.6/bin/mongod

Start mongo 3.6 version

/usr/local/opt/mongodb@3.6/bin/mongo

Run the important command

> db.adminCommand( { setFeatureCompatibilityVersion: "3.6" } )

...

最后，在卸载3.6之后，您可以安装最新版本4.x、 你不必指定@4.x等等，只是

Install the most current version

brew install mongodb