limits.conf
Adjust the Maximum Number of Open Files and Processes
In a secure cluster, if the DataNodes are started as the root user, JSVC downgrades the processing using setuid to hdfs. However, the ulimit is based on the ulimit of the root user, and the default ulimit values assigned to the root user for the maximum number of open files and processes may be too low for a secure cluster. This can result in a “Too Many Open Files” exception when the DataNodes are started.
Therefore, when configuring a secure cluster you should increase the following root ulimit values:
nofile: The maximum number of open files. Recommended value: 32768
nproc: The maximum number of processes. Recommended value: 65536
To set system-wide ulimits to these values, log in as root and add the
following lines to the /etc/security/limits.conf
file on
every host in your
cluster:
* - nofile 32768 * - nproc 65536
To set only the root user ulimits to these values, log in as root and add the
following lines to the /etc/security/limits.conf
file.
root - nofile 32768 root - nproc 65536
You can use the ulimit -a command to view the current settings:
[root@node-1 /]# ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 14874 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 14874 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
You can also use the ulimit command to dynamically set these limits until the
next reboot. This method sets a temporary value that will revert to the settings
in the /etc/security/limits.conf
file after the next reboot,
but it is useful for experimenting with limit settings. For example:
[root@node-1 /]# ulimit -n 32768
The updated value can then be displayed:
[root@node-1 /]# ulimit -n 32768