When the SU switch user error: Unable to set User id: resource is temporarily unavailable

today, when using the SU Switch User Doiido, the following error occurred:
# Su-doiido
SU: Unable to set User id: Resource is temporarily unavailable

Doiido user connections are not available with remote SSH tools such as SECURECRT.
find the relevant information, found in CentOS 6, there is a/etc/security/limits.d/90-nproc.config file, this file limits the maximum number of threads for a user of normal permissions, when the maximum number of threads for this user max user Processes reach the maximum limit, you cannot connect to the login. Therefore, you can modify this parameter only if you cannot reduce the thread, as follows:

1. View MAX User Processes

# Su-doiido

SU: Unable to set User id: resource is temporarily unavailable

# Ulimit-u
1024x768

It can be seen that the maximum number of threads is 1024x768
2. Modify MAX User Processes
# vi/etc/security/limits.d/90-nproc.conf
* Soft Nproc 1024x768
Root Soft Nproc Unlimited

It can be seen that all users except the root user are limited to 1024, so the problem can be resolved by annotating this line or by changing the value to
after the modification is complete, save and exit, such modification is effective immediately (tested successfully)

When the SU switch user error: Unable to set User id: resource is temporarily unavailable