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This is related to my question in stackoverflow where simply hang on updating a mongodb query.

After long soul searching we check the log. The log is 3GB in size.

A log with that size is absolutely useless. I cannot have any text editor to open it.

How to keep the log of mongodb small, say 50 mb max.

We are only interested in the last few commmand anyway not the whole log.

Is there a setting for that in MongoDB? If so what settings:

Note: The question is simmilar with:

However, that question doesn't ask

How do I do so by changing some text files or something persistent so that the setting remain every time I start mongodb.

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Check this post, it holds the same question. – SwissCoder Oct 9 '12 at 9:28
For a 3GB text file, you may find a pager more helpful than a text editor. Just sayin'. Also see grep, awk, sed, less, tail, head, and tac. – Chris Travers Oct 9 '12 at 10:05
By the way should I delete this question due to the exact duplicate? – Jim Thio Oct 9 '12 at 10:13
Actually I modified the question a little bit. I want to know how to do so permanently or set that as default. – Jim Thio Oct 9 '12 at 10:16

2 Answers 2

Have a look at log rotation. mongo log rotation

It will allow you to automatically create multiple smaller log files, much like web server logs. Just delete the older ones as you go.

And as Chris points out, you just need a decent text processor that can accommodate 3GB files. The list is surprisingly short on those that properly memory map files, but notepad certainly isn't one of them as it just tries to load the whole file into RAM like many others. Alternatives are easy to find, but your mileage may vary: large gb text editors

Personally, I keep "tail -f" running on my Mongo log file and it's always running in an window I can refer to.

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You might already know the answer just posting the answer here for someone else like me ending in this post :D

vi /etc/mongo.conf
smallfiles = true

This would set smallfiles true once you restart your mongodb.


Rounding a little bit more the answer smallfiles option in mongo what does is reducing the initial and journal data files size, this is useful if your machine do not have to much space or if you are gonna have multiple databases with small data each.

I my personal opinion smallfiles do not increase performance but like mentioned before could help for this specific scenarios another example is with Docker if you are not using -v "path/to/local/drive:"/data/db" then is better to set smallfiles true in my case if i don't the container breaks because it can't allocate the default data file space.

To add smallfiles to the mongo.conf you can do:

echo "smallfiles = true" >> /etc/mongo.conf
service mongod restart

More detailed info here:

Hope this helps :D

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@Erik just add an update with info let me know if this is good enough :D and thanks for your comment. – Angel Ramirez Leyva Aug 31 at 16:37
Thanks for the extra info! – Erik Aug 31 at 16:42

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