Debian11.3 : 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

huong@debian:~$ dpkg -l | grep vim
ii vim-common 2:8.2.2434-3+deb11u1 all Vi IMproved - Common files
ii vim-tiny 2:8.2.2434-3+deb11u1 amd64 Vi IMproved - enhanced vi editor - compact version

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

The "huong@debian:~$" will be abbreviated to "$" and "root@debian:~#" will be abbreviated to "#". In addition, we will proceed with the work as the root user.

1.2 Installing the vim package

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

$ su -
Password :  ←Root user password created during the installation process of Debian 11.3
# apt install -y vim
After installation, check the vim package again with the dpkg command

ii vim 2:8.2.2434-3+deb11u1 amd64 Vi IMproved - enhanced vi editor
ii vim-common 2:8.2.2434-3+deb11u1 all Vi IMproved - Common files
ii vim-runtime 2:8.2.2434-3+deb11u1 all Vi IMproved - Runtime files
ii vim-tiny 2:8.2.2434-3+deb11u1 amd64 Vi IMproved - enhanced vi editor - compact version

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

# update-alternatives --set editor /usr/bin/vim.basic
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in manual mode

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/".

#  vi ~/.vimrc

"Enables pasting and copying of text
set clipboard+=autoselect
" Use vim's own extensions (not compatible with vi)
set nocompatible
" Specify character code
set encoding=utf-8
" Specify file encoding
set fileencodings=utf-8,iso-2022-jp,sjis,euc-jp
" Specify the line feed code to be automatically recognized
set fileformats=unix,dos
" Obtain a backup
"The opposite is[ set nobackup ]
set backup
" Specify the directory from which to obtain backups
set backupdir=~/backup
" Specify the directory from which to obtain backups
set backupdir=~/backup
" Number of generations to keep search history
set history=50
" Do not distinguish between upper and lower case letters when searching
set ignorecase
" Mixing capital letters in search terms makes the search case sensitive
set smartcase
" Highlight words matching your search term
"The opposite is[ set nohlsearch ]
set hlsearch
" Use incremental search
"The opposite is [ set noincsearch ]
set incsearch
" Display line numbers
"The opposite is [ set nonumber ]
set number
" Visualize line breaks ( $ ) and tabs ( ^I )
set list
" Highlight corresponding parentheses when typing parentheses
set showmatch
" No newlines at the end of files
set binary noeol
"Enable automatic indentation
"The opposite is [ noautoindent ]
set autoindent
" Color-coded display by syntax
"The opposite is [ syntax off ]
syntax on
"Change color of comment text in case of [ syntax on ]
highlight Comment ctermfg=LightCyan
" Wrap lines by window width
"The opposite is [ set nowrap ]
set wrap
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 "debian-user".

# hostnamectl set-hostname debian-user

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

# cat /etc/hostname

2.2 Set IP address to network interface

The IP address is set to DHCP (dynamic IP address) when Debian 11 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.

# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:1b:55:05 brd ff:ff:ff:ff:ff:ff
altname enp2s1
inet brd scope global dynamic ens33
valid_lft 166871sec preferred_lft 166871sec
inet6 fe80::20c:29ff:fe1b:5505/64 scope link
valid_lft forever preferred_lft forever

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.

# vi /etc/network/interfaces
Default values are as follows
# The primary network interface
allow-hotplug ens33
iface ens33 inet dhcpChange as follows
# The primary network interface
allow-hotplug ens33
#iface ens33 inet dhcp  ←comment-out
# network interface settings
iface ens33 inet static

2.4 Enable static IP address

# systemctl restart networking ifup@ens33

3. Set server time synchronization

set up "timesyncd".

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.

# cp -p /etc/systemd/timesyncd.conf /etc/systemd/
# vi /etc/systemd/timesyncd.conf
Default values are as follows
[Time] #NTP=

3.2 Reflection of timesyncd service settings

# systemctl restart systemd-timesyncd

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

# timedatectl status
Local time: Thu 2022-06-02 03:05:15 EDT
Universal time: Thu 2022-06-02 07:05:15 UTC
RTC time: Thu 2022-06-02 07:05:15
Time zone: America/New_York (EDT, -0400)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no

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

# groupadd wheel

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".

# usermod -g wheel lan

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

# id lan
uid=1000(lan) gid=1001(wheel) groups=1001(wheel)

4.2 Edit configuration file for su command

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

# Uncomment this to force users to be a member of group wheel
# before they can use `su'. You can also add "group=foo"
# to the end of this line if you want to use a group other
# than the default "wheel" (but this may have side effect of
# denying "root" user, unless she's a member of "foo" or explicitly
# permitted earlier by e.g. "sufficient").
# (Replaces the `SU_WHEEL_ONLY' option from login.defs)
auth required  ← Uncomment

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.

# cd /etc/apt/
# cp sources.list sources.list_back
# vi /etc/apt/sources.list


#deb cdrom:[Debian GNU/Linux 11.3.0 _Bullseye_ - Official amd64 NETINST 20220326-11:22]/ bullseye main

deb bullseye main
deb-src bullseye main

deb bullseye-security main
deb-src bullseye-security main

# bullseye-updates, to get updates before a point release is made;
# see
deb bullseye-updates main
deb-src bullseye-updates main

# This system was installed using small removable media
# (e.g. netinst, live or single CD). The matching "deb cdrom"
# entries were disabled at the end of the installation process.
# For information about how to configure apt package sources,
# see the sources.list(5) manual.

The top one is the media used during installation. It is no longer used and has been commented out.
If used in the U.S., it should be a mirror with us.

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

# apt install -y locate
# dpkg -l | grep locate
ii locate 4.8.0-1 amd64 maintain and query an index of a directory tree

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

6.2 Create database

# updatedb

6.3 Running the locate command

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

# locate sshd

A list of filenames containing sshd is now displayed.

7. Locale Settings

This is the language setting for the Linux system; if you selected English as the locale when you installed Debian, you do not need to change it since the environment is originally English.

7.1 Check current locale

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

# localectl status
System Locale: LANG=en_US.UTF-8
VC Keymap: n/a
X11 Layout: jp
X11 Model: pc105

In the above case, "en_US.UTF-8" is the locale

8. Time zone settings

In most cases, the time zone for Debian 11 is set during installation, but if the US time zone "EDT" 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

# timedatectl status
Local time: Thu 2022-06-02 03:24:39 EDT
Universal time: Thu 2022-06-02 07:24:39 UTC
RTC time: Thu 2022-06-02 07:24:39
Time zone: America/New_York (EDT, -0400)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no

The time zone is set to "America/New_York(EDT, -0400)" 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.

# timedatectl set-timezone Asia/Tokyo

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

# apt update
Get:1 bullseye-security InRelease [44.1 kB] Get:2 bullseye-security/main Sources [123 kB] Get:3 bullseye-security/main amd64 Packages [153 kB] Hit:4 bullseye InRelease
Get:5 bullseye-updates InRelease [39.4 kB] Fetched 359 kB in 1s (297 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
All packages are up to date.

To update a package, run the "apt upgrade" command.

# apt upgrade -y
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.