Modifying OS Configuration

Disabling the OS Firewall

To ensure that the MogDB can work properly when the firewall is enabled, related services, protocols, IP addresses, and ports need to be added to the firewall whitelist of each host in the MogDB.

Take openEuler OS as an example. Assume that the MogDB information is listed in Table 1.

Table 1 Information of MogDB

Host Name	Internal IP Address	External IP Address
plat1	192.168.0.11	10.10.0.11
plat2	192.168.0.12	10.10.0.12
plat3	192.168.0.13	10.10.0.13
plat4	192.168.0.14	10.10.0.14
Management network	-	10.10.64.236

Procedure

Currently, EulerOS can be installed only when the firewall is disabled.

Set the value of SELINUX in the /etc/selinux/config file to disabled. a. Run the vim command to open the config file.
```
vim /etc/selinux/config
```
b. Change the value of SELINUX to disabled and run the :wq command to save the change and exit.
```
SELINUX=disabled
```
Restart the OS.
```
reboot
```
Check whether the firewall is disabled.
```
systemctl status firewalld
```
If the firewall status is active (running), the firewall is not disabled. Go to 4.

If the firewall status is inactive (dead), you do not need to disable the firewall.

Disable the firewall.

systemctl disable firewalld.service
systemctl stop firewalld.service

Repeat steps 1 to 4 on other hosts.

Setting Character Set Parameters

Set the same character set for all database nodes. You can add export LANG=Unicode in the /etc/profile file.

vim /etc/profile

Setting the Time Zone and Time

Set the same time zone for all database nodes by copying the /etc/localtime time zone file to the /usr/share/zoneinfo/ directory.

cp /usr/share/zoneinfo/$Locale/$Time zone /etc/localtime

NOTE: $Locale/$Time zone indicates the locale and time zone to be set, for example, Asia/Shanghai.

Run the date -s command to set the time of each host to the same time. For example:

date -s "Sat Sep 27 16:00:07 CST 2020"

NOTE: You can run the date command to query the time zone of the host.

(Optional) Disabling the Swap Memory

Note: Disabling the swap memory ensures the access performance of the database and prevents the buffer memory of the database from being evicted to the disk. If the server memory is small and the memory is overloaded, you can enable the swap memory to ensure normal running.

Run the swapoff -a command on each database node to disable the swap memory.

swapoff -a

Setting the NIC MTU

Set the NIC MTU value on each database node to the same value. For x86, the recommended MTU value is 1500. For ARM, the recommended MTU value is 8192.

ifconfig NIC ID mtu Value

Disabling RemoveIPC

On each database node, disable RemoveIPC. For CentOS, skip this step.

Procedure

Change the value of RemoveIPC in the /etc/systemd/logind.conf file to no. .

a. Run the vim command to open the logind.conf file.
```
vim  /etc/systemd/logind.conf
```
b. Change the value of RemoveIPC to no.
```
RemoveIPC=no
```
Change the value of RemoveIPC in the /usr/lib/systemd/system/systemd-logind.service file to no.

a. Run the vim command to open the systemd-logind.service file.
```
vim /usr/lib/systemd/system/systemd-logind.service
```
b. Change the value of RemoveIPC to no.
```
RemoveIPC=no
```

Reload configuration parameters.

systemctl daemon-reload
systemctl restart systemd-logind

Check whether the modification takes effect.

loginctl show-session | grep RemoveIPC
systemctl show systemd-logind | grep RemoveIPC

Repeat steps 1 to 4 on other hosts.

During the MogDB installation, the user root is required for remote login. This section describes how to set the user root for remote login.

Modify the PermitRootLogin configuration to enable remote login of user root.

a. Open the sshd_config file.
```
vim /etc/ssh/sshd_config
```
b. Modify permissions of user root using either of the following methods:
- Comment out PermitRootLogin no.
```
#PermitRootLogin no
```
- Set the value of PermitRootLogin to yes.
```
PermitRootLogin yes
```
c. Run the :wq command to save the modification and exit.
Modify the Banner configuration to delete the welcome information displayed when you connect to the system. The welcome information affects the return result of remote operations during the installation.

a. Open the sshd_config file.
```
vim /etc/ssh/sshd_config
```
b. Comment out the line where Banner is located.
```
#Banner XXXX
```
c. Run the :wq command to save the modification and exit.
Run the following command to validate the settings:
```
systemctl restart sshd.service
```
Re-log in to the system as user root.
```
ssh xxx.xxx.xxx.xxx
```
NOTE: xxx.xxx.xxx.xxx indicates the IP address of the MogDB installation environment.

Dynamically Disabling Transparent Huge Page

echo never > /sys/kernel/mm/transparent_hugepage/enabled

For example: openEuler

/root~ # cat /etc/system-release
openEuler release 20.03 (LTS)
/etc/default~ # echo never > /sys/kernel/mm/transparent_hugepage/enabled
/etc/default~ # cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]

If the transparent huge page function is successfully disabled, [never] will be displayed.

Disabling the transparent huge page function can reduce the overhead of the host OS to achieve more stable performance.

Issue