Modifying System Configuration Items

Perform the operations in this section on CentOS 8.1 only. Skip this section for other OSs.

Modifying limits.conf

Edit the /etc/security/limits.conf file.
```
vim /etc/security/limits.conf
```
Press i to enter the insert mode and add the following content to the end of the file:
```
* soft nofile 65536
* hard nofile 65536
* soft nproc 131072
* hard nproc 131072
```
Press Esc, type :wq!, and press Enter to save the file and exit.

Restarting the OS

Restart the OS for the previous modification to take effect.
```
reboot
```
Verify that the new configuration takes effect.
```
sestatus
```
```
ulimit -n
```

Optimizing Kernel Parameters

Edit the /etc/sysctl.conf file.
```
vim /etc/sysctl.conf
```

Press i to enter the insert mode and add the following content to the file:

kernel.shmmax = 500000000
kernel.shmmni = 4096
kernel.shmall = 4000000000
kernel.sem = 250 512000 100 2048
kernel.sysrq = 1
kernel.core_uses_pid = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.msgmni = 2048
net.ipv4.tcp_syncookies = 1
net.ipv4.ip_forward = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.tcp_max_syn_backlog = 4096
net.ipv4.conf.all.arp_filter = 1
net.ipv4.ip_local_port_range = 1025 65535
net.core.netdev_max_backlog = 10000
net.core.rmem_max = 2097152
net.core.wmem_max = 2097152
vm.overcommit_memory = 2

Press Esc, type :wq!, and press Enter to save the file and exit.
Make the configuration take effect.
```
sysctl -p
```

Configuring resolv.conf

View the resolv.conf file.
```
ls /etc/resolv.conf
```
Open the resolv.conf file.
```
vim /etc/resolv.conf
```

Press i to enter the insert mode and add the following content to the file:

# Generated by NetworkManager
nameserver 114.114.114.114
nameserver 8.8.8.8

Press Esc, type :wq!, and press Enter to save the file and exit.
View the resolv.conf file.
```
cat /etc/resolv.conf
```

Parent topic: Configuring the Compilation Environment