Shulou(Shulou.com)06/02 Report--

AIX Study-- configuration of user access system resource restrictions

The system resource limit used by Aix users includes two concepts-hard limit (hard limits) and soft limit (soft limits). Hard limits has been introduced since Aix version 4.1. The hard limits should be set by the Aix system administrator, and only members of the security group can increase this value, and the user can decrease this limit, but its changes will become invalid as the user exits from the system.

Use the following command to view the limit value for hard limits: ulimit-Hasoft limits is the upper limit used by the Aix core to limit the use of system resources by the process. This value can be changed by anyone, but cannot exceed the hard values. It is important to note that only members of the security group can make the changes permanent, and the changes made by the average Aix user will become invalid after they exit the system.

Use the following command to view the settings for soft limits: ulimit-a

The following are the default values for the system's soft limits:

3.2 4.1-4.3 = fsize = 2097151 fsize = 2097151 core = 2048 core = 2048 cpu = 3600 cpu =-1 data = 131072 data = 262144 rss = 65536 rss = 8192 stack = 65536 nofiles=2000 * nofiles=2000 *

* this value (nofiles) can only be changed in Aix 4.3.1 or later.

The above definition is stored as the default value in the file / etc/security/limits and takes effect after the new user is added to the system. Directly changing the defined values in this file requires a system restart for the changes to take effect. Setting the corresponding value to "- 1" indicates that it is not subject to the restrictions of soft limits (unlimited).

We will introduce each field one by one:

File size limit created by fsize users. This defined value, in 512 bytes, is the maximum file size that the user can generate.

The limit on the size of the core file generated by core (in 512 bytes).

The limited value (in seconds) of cpu available to cpu user processes. The average user can only decrease this value, and root can increase it. It is important to note that the time a process uses CPU depends on the Aix Kernel (core program) process scheduling algorithm, which is for reference only.

The limit, in bytes, for the segment size of the data process.

The limit, in bytes, for the stack segment size of the stack process.

The limit, in bytes, for the resident memory segment of the rss process. The Aix core does not refer to this limitation.

The maximum number of open files in the nofiles process. This limit is fixed at 2000 in versions prior to Aix 4.3.1. This value can be increased to 32767 in Aix 4.3.1 and later.

Among Aix users, there are three ways to modify the above limits:

1. Edit the file / etc/security/limits to modify the defined values directly. This change takes effect after the system restarts.

two。 Use the command ulimit to modify the default values. For example:

Ulimit-f value ulimit-c ulimit-t ulimit-d ulimit-s ulimit-m ulimit-n

The soft values for fsize, core, cpu,data, stack, rss, and nofiles will be modified.

3. Use the command chuser to modify the limit value of a user. For example:

Chuser fsize= chuser core=

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