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I needed to upgrade mongodb from 3.2 to 3.6 in my environment. For the process i first migrated from 3.2 to 3.4 as recommended. After successful migration to 3.4, i started migration to 3.6 i am not able to start mongod. When checked log file i found error like: IMPORTANT: UPGRADE PROBLEM: The data files need to be fully upgraded to version 3.4 before attempting an upgrade to 3.6; see http://dochub.mongodb.org/core/3.6-upgrade-fcv for more details.

MY Mongod.conf

systemLog: destination: file logAppend: true path: /var/log/mongodb/mongod.log

storage: dbPath: /var/lib/mongo journal: enabled: true

processManagement: fork: true # fork and run in background pidFilePath: /var/run/mongodb/mongod.pid # location of pidfile

net: port: 27017 bindIp: 127.0.0.1

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2 Answers 2

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58

I have similar problem, I've upgraded on Ubuntu 16.04 from MongoDB 3.4 to 3.6 but I missed this important step

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

Then I must downgrade to 3.4 to do it and then upgrade to 3.6 again. Here is the detail steps:

1. Uninstall 3.6

Backup /etc/mongod.conf
Backup /etc/apt/sources.list.d/mongodb-org-3.6.listed (rename or move it to another folder)

sudo apt-get update sudo apt-get remove mongodb-org-mongos mongodb-org-server mongodb-org-shell mongodb-org-tools

2. Re-install 3.4
Check folder /etc/apt/sources.list.d/ to see if this file exists or not: mongodb-org-3.4.list. If it does not exist, you can re-create by this command:

echo "deb [ arch=amd64,arm64 ] http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.4.list

then install by apt-get

sudo apt-get update sudo apt-get install -y mongodb-org mongod --version sudo systemctl start mongod

In my case the command systemctl start mongod return error Failed to start mongod.service: Unit mongod.service not found I resolved by these commands:

sudo systemctl enable mongod sudo service mongod restart sudo service mongod status

3. Execute very important command
After downgrade to 3.4, run this

mongo MongoDB shell version v3.4.10 connecting to: mongodb://127.0.0.1:27017 MongoDB server version: 3.4.10 > db.adminCommand( { setFeatureCompatibilityVersion: "3.4" } ) { "featureCompatibilityVersion" : "3.4", "ok" : 1 } > exit

4. Upgrade 3.6 again
Restore this file /etc/apt/sources.list.d/mongodb-org-3.6.listed

sudo apt-get update sudo apt-get install mongodb-org-mongos mongodb-org-server mongodb-org-shell mongodb-org-tools

Restore /etc/mongod.conf. Now, MongoDB 3.6 started without any problem

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7 Comments

Just a small correction, apt-get is missing on these commands: sudo remove mongodb-org-mongos sudo remove mongodb-org-server sudo remove mongodb-org-shell sudo remove mongodb-org-tools
And a little recommendation: check setFeatureCompatibilityVersion on all the replica set members with: db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } ) (docs.mongodb.com/manual/release-notes/3.6-upgrade-replica-set/…)
I had to add --allow-unauthenticated during step "2. Re-install 3.4" sudo apt-get install -y mongodb-org --allow-unauthenticated
I had to add the repo-key for mongodb-org: sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6
very helpful - I missed the same step and this allowed me to recover
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3

This may be the case when your db folder contains old mongoDB database format (like 3.4)

here is a useful hack if you don't mind LOOSING ALL YOUR DATA

  • After saving it you can delete the content of /data/db folder (ubuntu/linux mint)
  • Then restart mongod, then it should work normally
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4 Comments

This works well, given that the data hosted in the folder is not needed and so can be deleted.
But this cannot solve the problem which the old data is stored, and I want the old data back
The /data/db folder cannot be removed because you will lose all your data. This is a workaround not a solution
Oh no, this will delete all your existing data. Please be mindful of such cases

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