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Debian12 ; Initialization

1.Installing and configuring the vim editor

Debian has "nano" as the default editor. nano is somewhat difficult to use, and there are few environments where it is used, so we will introduce the procedure for changing the editor to "vim".。

1.1 Check vim package

Debian has vim installed by default, but it is a package called "vim-tiny", which is a less functional version. Let's check the installed vim package.
Debian uses the "dpkg" command to check packages. The "-l" option displays a list of packages.

Since the "dpkg" command as is will show all packages installed on the system, we will use the "grep" command to extract only those packages that contain the string "vim". Execute as follows

You can see that only the "vim-tiny" package is installed as shown above.

1.2  Installing the vim package

The "-y" option to the apt install command is an option that automatically confirms the installation.

Vim is installed as shown above.

1.3   Change the editor used by default

Change the default editor to "vim" installed from nano.
To change the default editor, run the command "update-alternatives --set editor".
To change to vim, run the following

If the output looks like the above, the editor has been changed.

1.4 Change vim settings

To allow all users, create a ".vimrc" file in "/root/".
To create a vim environment for each user, create a ".vimrc" file in the user's home directory.
This time, we will create a ".vimrc" file in the root user's home directory "/root/".

Comment out any unnecessary items above.

1.5 Activation of vim configuration changes

Please log out of the system for the settings to take effect. When you log in to the system again, the above information will be reflected.

2.Network Settings

2.1 Host Name Settings

This section describes cases where the hostname is set during Debian installation, but the hostname is changed for some reason.
Use the "hostnamectl set-hostname" command to set the hostname.
As an example, set "Lepard".

The result of the configuration can be checked by referring to the "/etc/hostname" file.

2.2 Set IP address to network interface

The IP address is set to DHCP (dynamic IP address) when Debian 12 is installed, so set a fixed IP address.
Modify the "/etc/network/interfaces" file to set the IP address, and then restart the network interface (ens33 in this case).
The network interface name will vary depending on the environment in which the setup was performed, so check the interface name first.
The command to check network information is "ip addr". Running this command will display the network interface name and IP address information.

Here, "ens33" is the "network interface name. lo" is the "local loopback interface" and is not normally used.

2.3 Setting up a static IP address

We proceed assuming the following information necessary for the network configuration and the parameters to be configured this time.

・IP address
・subnet mask
・default gateway
・DNS Server

IP addresses are set by modifying the "/etc/network/interfaces" file.

2.4 Enable static IP address

3. Set server time synchronization

3.1 Configuration of timesyncd service

The timesyncd service is configured in the file "/etc/systemd/timesyncd.conf". Before changing the file, make a backup copy of the original file.

We will edit the configuration file.

3.2 Reflection of timesyncd service settings

If no error is output, the service has restarted.
Check the time synchronization. The "timedatectl status" command is used to check the time synchronization. Execute the command as follows

If "System clock synchronized: yes" is displayed, the time is synchronized.

4.  Restrict users who can su

In Debian, any user can be changed to the root user with the "su" command in the default configuration.
If multiple users are created on the server, limit the number of users who can execute the su command as much as possible, because if the login information of any one of the users is known, the root user privilege can be taken away with the su command after unauthorized access.
Allow only users belonging to the wheel group to be authorized to execute su.

4.1 Adding users to the wheel group

First, create a wheel group with the following command

Run the usermod command to add a user to the wheel group. As an example, let us assume that the user to be added is "lan".

Confirm that the wheel group is added to the wheel group using the id command.

4.2 Edit configuration file for su command

The configuration file for the su command is /etc/pam.d/su. (around line 15)

The lan user can now transition to root privileges using the "su -" command.

5. Debian Repository Mirror Settings Edit

The repository mirror configuration file is /etc/apt/sources.list, make a copy and edit it.

The file contents

The top one is the media used during installation. It is no longer used and has been commented out.
Add Backports repository (add the following to the last line)

Update source list

6. Make the locate command available

To search for a specific file on the entire Linux system, use the find command, but find's options are somewhat confusing.
The locate command can extract all files with a given filename.
Although a database of file and folder names must be created in advance, it has the advantage of being fast and easy to use. The "locate" command can be used here.

6.1 Installing the locate package

If the locate package name appears in the execution result as shown above, the installation has been verified.

6.2 Create database

6.3 Running the locate command

As an example, search for all files named "sshd".

A list of filenames containing sshd is now displayed.

7.Locale Settings

If you have selected Japanese as your locale when installing Debian, you are already in a Japanese environment and do not need to change it.
If your environment is "English locale" and you prefer to use Japanese locale, please do so.

7.1 Check current locale

Check the locale set in the system. Use the "localectl status" command to check the locale.

In the above case, "C.UTF-8" is the locale, which means C locale (POSIX locale).

7.2 Changed to Japanese locale

In Debian, a list of locales can be found with the command "localectl list-locales". Run it to see which locales are available on your system.

Two locales are displayed. Since "ja_JP.UTF-8" in the displayed results is the locale for Japanese, set the "ja_JP.UTF-8" locale.
To set the locale, use the "localectl set-locale" command. Execute as follows

We have confirmed that the "ja_JP.UTF-8" locale is set as shown above.

8. Time zone settings

In most cases, the time zone for Debian 11 is set during installation, but if the Japanese time zone "JST" is not specified, it can be changed with the "timedatectl" command.

8.1 Display of current time zone

To check the time zone set on the server, run the "timedatectl status" command

The time zone is set to "Asia/Tokyo (JST)" as shown above.

8.2 Change time zone to Japan

If it is not "Asia/Tokyo (JST)", you can change the time zone with the "timedatectl set-timezone" command.

9. Update system packages

Debian systems installed from the media may contain outdated packages. Debian also uses "apt" to update all packages.
To see only the list of packages to be updated without updating the packages, run the "apt update" command. The command is executed as follows

In this case, all packages have been updated, but if you need to update any of them, run the "apt upgrade" command.

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