Which command is used to restrict access to system resources for each user account?

The command used to restrict access to system resources for each user account is the one that adjusts resource limits on a per-user basis. This is achieved using the ulimit command. It allows users and administrators to set limits on various types of resources such as the maximum size of files created, the maximum number of processes that can be run, and the maximum amount of memory that can be allocated.

Using ulimit, you can establish quotas that help prevent users from consuming too many resources, which is crucial for maintaining system performance and ensuring fair resource allocation among users. This command is particularly important in multi-user environments where resource contention can affect the overall stability and responsiveness of the system.

In contrast, the other commands serve different purposes: setenforce and getenforce are related to managing SELinux modes, and chage is used to modify password expiration information. Hence, they do not pertain to managing user resource limits in the same direct way that ulimit does.