Our cloud based systems use Java and require greater than 1024 for the max file descriptor limit. On one of our virtual systems, every time we try to make this change, I can get it to change and it will be persistent across the first reboot (have not tested multiple), but if we stop and start our java app, the limit seems to get reset to 1024.
System info:
Linux mx.xen16.node01002 3.1.0-1.2-xen #1 SMP Thu Nov 3 14:45:45 UTC 2011 (187dde0) x86_64 GNU/Linux
Here are the steps I took:
edited /etc/sysctl.conf and appended fs.file-max = 4096
Before applying, checked the limit for the process (PID 1530):
root 1530 6.7 31.0 1351472 165244 pts/0 Sl 17:12 0:58 java
cat /proc/1530/limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8388608 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes unlimited unlimited processes
Max open files 1024 1024 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 16382 16382 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us
Now I apply the change with:
sudo sysctl -p
fs.file-max = 4096 (ok it should be set)
I now do a reboot
When the system comes back up, the java app starts automatically and using the new PID I check the limits again.
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8388608 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes 3818 3818 processes
Max open files 4096 4096 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 3818 3818 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us
The limit is set correctly, however if I start and stop the java app, the limit defaults back to 1024. There is not an issue with the java app. This is one of SEVERAL identical cloud based systems around the world, each one a copy of this one. This VM resides at Gigatux. We have several other identical systems at Giga running the same OS, same version, and same app and app version. Only this one is behaving strangely. Please help.
* UPDATE *
I removed the statement from the end of the sysctl.conf per David's recommendation. If I issue ulimit -n, the limit is indeed set to 4092. If I look in /etc/security/limits.conf, you can see the limits configured here as well.
* hard nofile 4096
* soft nofile 4096
Yet if I restart the java process, it still defaults back to 1024.
agent@mx:~$ cat /proc/2432/limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8388608 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes unlimited unlimited processes
Max open files 1024 1024 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 16382 16382 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us
agent@mx:~$ echo -n $SHELL ' ' && ulimit -n
/bin/bash 4096
* UPDATE *
Ok, I think this may be fixed. I changed the following:
* hard nofile 4096
* soft nofile 4096
back to the following:
root hard nofile 4096
root soft nofile 4096
and the issue appears to be resolved
Best Answer
There's two places the limit gets set, you've changed one of them (sysctl) but you've forgotten that the shell environment that Java runs under also sets its own limit which may be equal to or less than the system limit:
So, figure out which shell Java gets launched from, and set the limit with the built in shell command. For example "ulimit" in bash.