Linux security & performance tuning - others

1. check existing limits : 

[root@test3 security]# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 63699
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024

pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 63699
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

 

2. Errors and logs : 

1) log location  : var/log/secure

2) Error 1 : 

May  6 13:16:35 test3 sshd[9800]: subsystem request for sftp
May  6 13:16:35 test3 sshd[9800]: error: do_exec_no_pty: fork: Resource temporarily unavailable
May  6 13:16:35 test3 sshd[9800]: subsystem request for sftp failed, subsystem not found

file changed : /etc/security/limits.conf
 -- changed open files to  4096 from 1024; 
 -- changed max user processes(hard & soft)  to  128376 from  63699
 -- user maxlogins added : 1000

3)Error 2 : no more sessions

 file changed : /etc/ssh/sshd_config
--MaxSessions 10240  from 1000
--MaxStartups 10240  from 1000

much less "no more sessions" error now but still some 

4) file changed : /etc/security/limits.conf 
-- change maxlogins from 1000 to 2000  (this may not help )

5) file changed : /etc/security/limits.d/90-nproc.conf   ( this control the max open sessions/concurrent logins for specific user : stormReportsUat  , help "no more sessions" error
-- added stormRepUser   soft    nproc     10240