The status test enabled on the iptables service does not display the unknown key error.

The status test enabled on the iptables service does not display the unknown key error. We try to disable
Iptables.

[Root @ DT2MISPDB ~] # Service iptables stop
Flushing firewall rules: [OK]
Setting chains to policy ACCEPT: nat filter [OK]
Unloading iptables modules: [OK]
[Root @ DT2MISPDB ~] #
[Root @ DT2MISPDB etc] # service iptables status
Firewall is stopped.

[Root @ DT2MISPDB etc] # sysctl-p
Net. ipv4.ip _ forward = 0
Net. ipv4.conf. default. rp_filter = 1
Net. ipv4.conf. default. accept_source_route = 0
Kernel. sysrq = 0
Kernel. core_uses_pid = 1
Net. ipv4.tcp _ syncookies = 1
Kernel. msgmnb = 65536
Kernel. msgmax = 65536
Kernel. shmall = 2097152
Kernel. shmmax = 3221225472
Kernel. shmmni = 4096
Kernel. sem = 250 32000 100 128
Fs. file-max = 6815744
Net. ipv4.ip _ local_port_range = 9000 65500
Net. core. rmem_default = 262144
Net. core. rmem_max = 4194304
Net. core. wmem_default = 262144
Net. core. wmem_max = 1048576
Fs. aio-max-nr = 1048576
Error:
"Net. ipv4.ip _ conntrack_max" is an unknown key
[Root @ DT2MISPDB etc] #

Error found:
Error: "net. ipv4.ip _ conntrack_max" is an unknown key

Use modprobe to load the ip_conntrack module, and lsmod to check that the module has been loaded.

[Root @ DT2MISPDB etc] # modprobe ip_conntrack
[Root @ DT2MISPDB etc] # lsmod
Module Size Used
Ip_conntrack 53281 0

Disable the iptables service again and view
[Root @ DT2MISPDB etc] # service iptables stop
Flushing firewall rules: [OK]
Setting chains to policy ACCEPT: filter [OK]
Unloading iptables modules: [OK]
[Root @ DT2MISPDB etc] #

[Root @ DT2MISPDB etc] # lsmod
No ip_conntrack module was found.

Problem:
1. What does Linux mean by loading and detaching modules? All modules here refer to core modules?
2. What is the relationship between loading the ip_conntrack module and iptables service and using service iptables start?