How do I increase the open files limit for a non-root user?

Question

This is happening on Ubuntu Release 12.04 (precise) 64-bit Kernel Linux 3.2.0-25-virtual

I'm trying to increase the number of open files allowed for a user. This is for my eclipse java application where the current limit of 1024 is not enough.

According to the posts I've found so far, I should be able to put lines into

/etc/security/limits.conf like this:

soft nofile 4096
hard nofile 4096

to increase the number of open files allowed for all users.

But that's not working for me and I think the problem is not related to that file.

For all users, the default limit is 1024, regardless of what is in /etc/security/limits.conf (I rebooted after changing that file)

$ ulimit -n
1024

Now, despite the entries in /etc/security/limits.conf I can't increase that:

$ ulimit -n 2048

-bash: ulimit: open files: cannot modify limit: Operation not permitted The weird part is that I can change the limit downwards, but can't change it upwards - even to go back to a number which is below the original limit:

$ ulimit -n 800
$ ulimit -n
800

$ ulimit -n 900

-bash: ulimit: open files: cannot modify limit: Operation not permitted

As root, I can change that limit to whatever I want, up or down. It doesn't even seem to care about the supposedly system-wide limit in /proc/sys/fs/file-max

# cat /proc/sys/fs/file-max
188897

# ulimit -n 188898
# ulimit -n 
188898

But even I get eclipse to run as root, my application still crashes because of "Too Many Open File" exception!

So far, I haven't found any way to increase the open files limit for a non-root user.

How should I properly do this? I have looked at several other posts but no luck!

Answer 1

The ulimit command by default changes the HARD limits, which you (a user) can lower, but cannot raise.

Use the -S option to change the SOFT limit, which can range from 0-{HARD}.

I have actually aliased ulimit to ulimit -S, so it defaults to the soft limits all the time.

alias ulimit='ulimit -S'

As for your issue, you're missing a column in your entries in /etc/security/limits.conf.

There should be FOUR columns, but the first is missing in your example.

* soft nofile 4096
* hard nofile 4096

The first column describes WHO the limit is to apply for. '*' is a wildcard, meaning all users. To raise the limits for root, you have to explicitly enter 'root' instead of '*'.

You also need to edit /etc/pam.d/common-session* and add the following line to the end:

session required pam_limits.so

Answer 2

If you use soft and hard limits on a per user basis you can use something like:

su USER --shell /bin/bash --command "ulimit -n"

to check wether your settings are working for that specific user or not.

Answer 3

ulimit -S -n 4096

That should increase your soft limit for open files (-n) to 4096.

Answer 4

I have lots of trouble getting this to work.

Using the following allows you to update it regardless of your user permission.

sudo sysctl -w fs.inotify.max_user_watches=100000