[root@namenode01 backup]# su - app
Last login: Tue Apr 26 09:48:44 CST 2016 from application03 on pts/0
su: failed to execute /bin/bash: Resource temporarily unavailable

如上，提示资源不足

解决如下：

[root@namenode01 backup]# egrep -v "^$|^#" /etc/security/limits.d/20-nproc.conf 
*          soft    nproc     65535        #将默认值1024改为65535
root       soft    nproc     unlimited

验证结果

[root@namenode01 backup]# su - app
Last login: Tue Apr 26 10:38:20 CST 2016 on pts/0