Setting Limits for Users in Linux

We can set useful limits for users which is useful to control the resource utilization in Linux. This can be configured in /etc/security/limits.conf. To activate these limits you need to add the following line to the bottom of /etc/pam.d/login file in your Linux server.

session required /lib/security/pam_limits.so.

Entries in limits.conf file have the following structure:

[username or @groupname]          [type resource]        [limit]

Group names must be preceded by the @ to distinguish them from usernames.
The type must be either soft or hard. Soft-limits can be exceeded and are usually warning marks whereas hard-limits cannot be exceeded. A resource type can be one of the following keywords:

core	Limits the size of a core file (KB).
data	Maximum data size (KB).
fsize	Maximum file size (KB).
memlock	Maximum locked in memory address space (KB).
nofile	Maximum number of open files.
rss	Maximum resident set size (KB).
stack	Maximum stack size (KB).
cpu	Maximum CPU time in minutes.
nproc	Maximum number of processes.
as	Address space limit.
maxlogins	Maximum number of logins allowed for this user.

Below is example of limits.conf file. In this example, oracle user set to memlock limit of 12582912 and all the users in the server set with nproc and nofile limits.

# Added for Oracle Database Server

* soft nproc 2047

* hard nproc 16384

* soft nofile 1024

* hard nofile 65536

oracle soft memlock 12582912

oracle hard memlock 12582912

#*               soft    core            0

#*               hard    rss             10000

#@student        hard    nproc           20

#@faculty        soft    nproc           20

#@faculty        hard    nproc           50

#ftp             hard    nproc           0

#@student        -       maxlogins       4

# End of file

Author : LazySystemAdmin

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