On Linux systems, ulimit can be used to change resource limits on a temporary basis. Limits usually need to be set as root before switching to the user that will run Elasticsearch. For example, to set the number of open file handles (ulimit -n) to 65,536, you can do the following:

sudo su  
ulimit -n 65535 
su elasticsearch 

The new limit is only applied during the current session.

You can consult all currently applied limits with ulimit -a.

On Linux systems, persistent limits can be set for a particular user by editing the /etc/security/limits.conf file. To set the maximum number of open files for the elasticsearch user to 65,536, add the following line to the limits.conf file:

elasticsearch  -  nofile  65535

This change will only take effect the next time the elasticsearch user opens a new session.

Ubuntu and limits.conf

Ubuntu ignores the limits.conf file for processes started by init.d. To enable the limits.conf file, edit /etc/pam.d/su and uncomment the following line:

# session    required   pam_limits.so

When using the RPM or Debian packages, system settings and environment variables can be specified in the system configuration file, which is located in:

However, for systems which uses systemd, system limits need to be specified via systemd.

When using the RPM or Debian packages on systems that use systemd, system limits must be specified via systemd.

The systemd service file (/usr/lib/systemd/system/elasticsearch.service) contains the limits that are applied by default.

To override them, add a file called /etc/systemd/system/elasticsearch.service.d/override.conf (alternatively, you may run sudo systemctl edit elasticsearch which opens the file automatically inside your default editor). Set any changes in this file, such as:

[Service]
LimitMEMLOCK=infinity

Once finished, run the following command to reload units:

sudo systemctl daemon-reload