I'm using CentOS 6.3 64bit, and having trouble with increase FD limitation: SSH not working after changed the limitation, every-times I logged on my server, after typed password, then "connection closed by remote server".
It's a remote server without any "rescue mode" so there's no way to do a local login to get any error log. I also tried ulimit -SHn before this issue happened but not work as well.
Now I have to restore snapshot every-time this issue happened, and still have no idea what's wrong with my server.
Since I'm working on a high performance server handling millions of requests per second, I need a very high FD limitation, here is my configuration:
/etc/security/limits.conf
* hard nofile 2000000
* soft nofile 2000000
/etc/security/limits.d/90-nproc.conf
* soft nproc 1024
/etc/ssh/sshd_config
Protocol 2
SyslogFacility AUTHPRIV
PasswordAuthentication yes
ChallengeResponseAuthentication no
GSSAPIAuthentication yes
GSSAPICleanupCredentials yes
UsePAM yes
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
X11Forwarding yes
Subsystem sftp /usr/libexec/openssh/sftp-server
/etc/pam.d/sshd
auth required pam_sepermit.so
auth include password-auth
account required pam_nologin.so
account include password-auth
password include password-auth
session required pam_selinux.so close
session required pam_loginuid.so
session required pam_selinux.so open env_params
session optional pam_keyinit.so force revoke
session include password-auth
session required pam_limits.so
/etc/sysctl.conf
fs.file-max = 2000000
fs.nr_open = 2000000