ulimit Command
Purpose
The ulimit command sets or reports user process resource limits, as defined in the /etc/security/limits file. This file contains these default limits:
fsize = 2097151 , core = 2097151 , cpu = -1 , data = 262144, rss = 65536, stack = 65536
nofiles = 2000, threads = -1, nproc = -1
These values are used as default settings when a new user is added to the system. The values are set with the mkuser command when the user is added to the system, or changed with the chuser command.
Limits are categorized as either soft or hard. With the ulimit command, you can change your soft limits, up to the maximum set by the hard limits. You must have root user authority to change resource hard limits.
Many systems do not contain one or more of these limits. The limit for a specified resource is set when the Limit parameter is specified. The value of the Limit parameter can be a number in the unit specified with each resource, or the value unlimited. To set the specific ulimit to unlimited, use the word unlimited
Note: Setting the default limits in the /etc/security/limits file sets system wide limits, not just limits taken on by a user when that user is created
The current resource limit is printed when you omit the Limit parameter. The soft limit is printed unless you specify the -H flag. When you specify more than one resource, the limit name and unit is printed before the value. If no option is given, the -f flag is assumed.
Since the ulimit command affects the current shell environment, it is provided as a shell regular built-in command. If this command is called in a separate command execution environment, it does not affect the file size limit of the caller's environment. This would be the case in the following examples:
env ulimit 10000
Once a hard limit has been decreased by a process, it cannot be increased without root privilege, even to revert to the original limit.
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