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Ubuntu Server 25.10 Download & Install
1.Download the installation image
Ubuntu 25.10 (Questing Quokka) was released on October 9, 2025.
The Ubuntu 25.10 (Questing Quokka) installation image (ubuntu-25.10-live-server-amd64.iso) can be downloaded from the following site.
For general use, this version is an intermediate release provided between LTS and LTS and should be assumed to be “transferable to the next version within 9 months”.
If you expect to use it for a longer period of time, use 24.04.
2.Ubuntu Server 25.10 Install
Create an installation CD/DVD or USB disk from the downloaded ISO file, modify the BIOS settings to boot from the installation disk, and start the PC.
The installation procedure is the same as for Ubuntu Server 25.04, so it will be omitted here.
Please refer to the page below.
Set root password
In the default configuration of Ubuntu, the root user is unavailable because no password has been set.
By setting a password for the root user, transitions using the traditional [su] command will be possible.
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$ sudo passwd root [sudo] password for [user name] ← Current user's password New password: ← Enter the password to be set Retype new password: ← again password passwd: password updated successfully |
Switch to root user
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$ su - Password:[Password set above] |
System Modernization
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# apt update # apt upgrade |
Make locate command available
The find command is often used to search for specific files throughout the Linux system, but find is somewhat confusing in terms of specifying options.
The locate command can extract all files with a specified filename.
1. Installing the locate package
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# apt install -y locate Check the package # dpkg -l | grep locate ii locate 4.10.0-3build1 amd64 maintain and query an index of a directory tree |
2. Example of executing the locate command
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# updatedb # locate sshd /etc/pam.d/sshd /etc/ssh/sshd_config /etc/ssh/sshd_config.d ・・・・ A list of filenames containing sshd will be displayed as shown above. |
vim editor settings
Ubuntu has vim installed by default
There may be cases where you do not want to allow vim settings for all users. In such cases, a ".vimrc" file can be created in each user's home directory to change the vim environment for each user.
In this case, we will create a ".vimrc" file in the root user's home directory "/root/" and apply it to all users.
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# vi ~/.vimrc |
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
" 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 the search term The reverse is [ set nohlsearch ].
set hlsearch
" Use incremental search (start searching for matching strings at any time while entering search terms)
set incsearch
" Display line numbers
set number
" Highlight corresponding parentheses when entering parentheses
set showmatch
" No newlines at the end of files
set binary noeol
" Enable automatic indentation]
set autoindent
" Color-coded display by syntax
syntax on
" [ Change color of comment text in case of [ syntax on ].
highlight Comment ctermfg=LightCyan
" Wrap lines by window width
set wrap
Select the above settings according to your preference.
Network Settings
1. Host Name Settings
This procedure is not necessary if you have already set the hostname at the time of Ubuntu installation and wish to use the hostname as it is.
To change the hostname, use the "hostnamectl set-hostname" command.
As an example, we set "Lepard" as the hostname.
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# hostnamectl set-hostname Lepard Confirmation of Settings Results # cat /etc/hostname Lepard |
2. Set IP address to network interface
If you specified a static IP address during Ubuntu installation, this section is unnecessary.
To change the IP address, modify the /etc/netplan/00-installer-config.yaml file, then restart the network interface (ens33 in this environment).
The network interface name varies depending on the setup environment, so first check the interface name.
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# 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 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host noprefixroute valid_lft forever preferred_lft forever 2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 00:0c:29:7a:ed:b0 brd ff:ff:ff:ff:ff:ff altname enp2s1 altname enx000c297aedb0 inet 192.168.11.83/24 brd 192.168.11.255 scope global ens33 valid_lft forever preferred_lft forever inet6 fe80::20c:29ff:fe7a:edb0/64 scope link proto kernel_ll valid_lft forever preferred_lft forever |
ens33:Network Interface Name
192.168.11.83 : IP Address
2.1 Setting up a static IP address
This time, we'll set the IP address to 192.168.11.63 as an example. The required network information is as follows, and this will be reflected in the configuration file.
Address : 192.168.11.63/24
Default gateway : 192.168.11.1
Name server : 192.168.11.1
IP address settings are configured by modifying the "/etc/netplan/00-installer-config.yaml" file.
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Disable the installer's default settings and back them up. # mv /etc/netplan/00-installer-config.yaml /etc/netplan/00-installer-config.yaml.bak Create a new installer configuration file # vi /etc/netplan/01-installer-config.yaml network: ethernets: ens33: addresses: - 192.168.11.63/24 nameservers: addresses: - 192.168.11.1 search: - korodes.com routes: - to: default via: 192.168.11.1 version: 2 # Apply settings # netplan apply |
2.2 Disabling IPv6
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# echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf # sysctl -p net.ipv6.conf.all.disable_ipv6 = 1 |
Configure server time synchronization
Starting with Ubuntu 25.10, the service that automatically synchronizes the server's time has been changed from system-timesyncd to chrony by default.
1. Configuration of the chronyd service
Configuration of the time synchronization server is performed in /etc/chrony/sources.d/ubuntu-ntp-pools.sources.
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# vi /etc/chrony/sources.d/ubuntu-ntp-pools.sources Lines 4-7: Comment them out and add the following below them. #pool 1.ntp.ubuntu.com iburst maxsources 1 nts prefer #pool 2.ntp.ubuntu.com iburst maxsources 1 nts prefer #pool 3.ntp.ubuntu.com iburst maxsources 1 nts prefer #pool 4.ntp.ubuntu.com iburst maxsources 1 nts prefer pool ntp.nict.jp iburst |
Restart chrony and enable it to remain active after a system reboot.
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# systemctl enable chrony.service # systemctl restart chrony.service |
Open the NTP port in the firewall (We'll explain firewalls on the next page, so just open it for now).
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# ufw enable # systemctl start ufw # ufw allow ntp # ufw reload |
2.Checking the status (operation) of chronyd
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# chronyc sources MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== ^+ ntp-nts-2.ps5.canonical.> 2 7 377 99 -6311us[-6357us] +/- 121ms ^+ ntp-nts-3.ps5.canonical.> 2 7 377 34 -5169us[-5223us] +/- 119ms ^+ ntp-nts-2.ps6.canonical.> 2 7 377 37 +8114us[+8060us] +/- 109ms ^* ntp-nts-3.ps6.canonical.> 2 6 373 4 +4125us[+4075us] +/- 111ms ^- ntp-nts-1.ps6.canonical.> 2 7 377 100 -1169us[-1215us] +/- 110ms |
If "System clock synchronized: yes" is displayed, the time is synchronized.
3. Set time zone to Japan
Current Time Zone Check
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# timedatectl status Local time: Mon 2026-01-12 02:04:03 UTC Universal time: Mon 2026-01-12 02:04:03 UTC RTC time: Mon 2026-01-12 02:04:03 Time zone: Etc/UTC (UTC, +0000) System clock synchronized: yes NTP service: active RTC in local TZ: no |
In the above, Time zone: Etc/UTC (UTC, +0000), so it matches Japan (Asia/Tokyo).
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# timedatectl set-timezone Asia/Tokyo # timedatectl status Local time: Mon 2026-01-12 11:04:40 JST Universal time: Mon 2026-01-12 02:04:40 UTC RTC time: Mon 2026-01-12 02:04:40 Time zone: Asia/Tokyo (JST, +0900) System clock synchronized: yes NTP service: active RTC in local TZ: no |
As above, it is in Japan.
