mongorestore and --db

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Jeff Abrahamson

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Oct 10, 2018, 5:30:08 AM10/10/18

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I have a script whose purpose is to restore a production mongodb snapshot to my staging mongodb instance. The key line in that script is this:

time mongorestore --ssl --gzip --drop --host=my_fqdn --port=27017 --username=my_restore_username --password=my_password --archive="$snapshot_name"

Unfortunately, that loads the database my_prod into the database my_prod. But I want to drop my_staging and load my_prod as my_staging. So I thought I needed a --db flag, thus:

time mongorestore --ssl --gzip --drop --db=my_staging_db --host=my_fqdn --port=27017 --username=my_restore_username --password=my_password --archive="$snapshot_name"

But that causes (I think) my_restore_username to connect against my_staging_db instead of against admin. (As per my understanding of the docs, I've created my_restore_user on admin rather than against any user database.) But that just gives me an immediate authentication error:

2018-10-10T04:28:28.418+0000 Failed: error connecting to db server: server returned error on SASL authentication step: Authentication failed.

In the mongod log that looks like this:

2018-10-10T04:57:41.907Z I ACCESS [conn23] SCRAM-SHA-1 authentication failed for my_restore_user on my_staging_db from client 1.2.3.4:55240 ; UserNotFound: Could not find user my_restore_user@my_staging_db

Fair enough. But is there a way to say "authenticate against admin, then restore database my_staging_db in place of the existing database my_staging_db"?

Alternatively, I could do a drop/restore as my_prod_db, then drop my_staging_db and rename my_prod_db to be my_staging_db. I'm concerned that that's fragile in the best of scenarios and certainly unnecessary.

Any pointers?

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Jeff Abrahamson
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Kevin Adistambha

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Oct 25, 2018, 1:36:06 AM10/25/18

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Hi Jeff,

But is there a way to say “authenticate against admin, then restore database my_staging_db in place of the existing database my_staging_db”?

I believe what you’re looking for is the —authenticationDatabase parameter in mongorestore. For example, you could use:

mongorestore --ssl --gzip ... --authenticationDatabase admin

to let mongorestore know that you intend to use admin as your authentication database.

On another note, instead of using the --db parameter, you could also use --nsFrom and --nsTo. The two parameters accept wildcard, so if you want to restore the wholemy_prod database to my_staging, your command line could be:

mongorestore  --ssl --gzip --drop --host=my_fqdn --port=27017 --username=my_restore_username --password=my_password --archive="$snapshot_name" --nsFrom="my_prod.*" --nsTo="my_staging.*" --authenticationDatabase=admin

The parameters --nsFrom and --nsTo should make your intent more explicit. They were added in MongoDB 3.4.