What does “soft/hard nofile” mean on Linux

Question

When I tried to install a software on RedHat EL5, I got the error that the expected value of soft/hard nofile is 4096 while the default is 1024. I managed to increase the number

Answer 1

No reboot is required, but /etc/security/limits.conf is only processed when /lib/security/pam_limits.so runs, which is at login time, and the values are inherited by child processes. After a new login, anything under that login will inherit the values specified.