Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Show current Postfix queue listing
Answer:
To show the current Postfix queue, you can try the command "postqueue"
# postqueue -p
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
BD7E2BF973 972 Sat Aug 27 08:57:54 [email protected]
(connect to alt4.gmail-smtp-in.l.google.com[209.85.143.27]:25: Connection timed out)
[email protected]
Select a document in MongoDB
Answer:
To select (find) a document in MongoDB, you can use the following syntax in the mongodb Interactive shell.
use my_db
db.users.find({name:"peter"})You need to switch to the current database (e.g. my_db) and then execute your select statement.
Post a file to a server using the Curl command
Answer:
You can simulate a HTTP form post, with a file being uploaded to a remote server using the curl command.
curl -F 'photo=@/upload/image.jpg' http://example.com/upload.phpAssume the name of the form element of your upload is called "photo"
Explain query execution plan in MongoDB
Answer:
Like MySQL, you can get a better understanding of the performance of your MongoDB's query, you can use the $explain feature.
E.g.
db.collection.find(query).explain();Debug and verify Postfix configurations
Answer:
A simple way to debug and verify your Postfix configurations is the use the sendmail command with the -bv flag.
Example:
# sendmail -bv [email protected]
No email will be sent using the above command, it just report after verifying each recipient address. This is very useful for testing the Postfix configurations.
