使用xshell无法连接远程centos服务器

原来一直是可以登录的，自从放假回来，再用xshell就登录不上了。网上搜了一大堆答案，好像都不行。
现象：1：日志内容（是我用root登录后查看的）Feb 6 11:07:19 hostA sshd[32309]: Accepted password for tomcat from 115.197.x.x port 27073 ssh2Feb 6 11:07:19 hostA sshd[32309]: pam_unix(sshd:session): session opened for user tomcat by (uid=0)Feb 6 11:07:19 hostA sshd[32311]: fatal: setresuid 500: Resource temporarily unavailableFeb 6 11:07:19 hostA sshd[32309]: pam_unix(sshd:session): session closed for user tomcat
2:xshell显示内容
Connecting to 114.215.x.x:22...Connection established.To escape to local shell, press Ctrl+Alt+].
Connection closed by foreign host.
Disconnected from remote host(testA) at 11:07:25.
Type `help' to learn how to use Xshell prompt.
3：使用root切换tomcat，报如下错误[root@hostA ~]# su tomcat
su: cannot set user id: Resource temporarily unavailable

===============================================================解决办法：1：vim /etc/security/limits.d/90-nproc.conf* soft nproc 65535 <---此数值该大点2：sysctl -p

另外：
nproc表示为用户进程数。
查看文件打开数：lsof |grep tomcat|wc -l

查看用户进程数：ps -U tomcat |wc -l

参考内容戳这里 <--