安装PostgreSQL

$ sudo apt install postgresql

(省略)

selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Asia/Tokyo
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok

Success. You can now start the database server using:

    pg_ctlcluster 12 main start

Ver Cluster Port Status Owner    Data directory              Log file
12  main    5432 down   postgres /var/lib/postgresql/12/main /var/log/postgresql/postgresql-12-main.log
update-alternatives: using /usr/share/postgresql/12/man/man1/postmaster.1.gz to provide /usr/share/man/man1/postmaster.1.gz (postmaster.1.gz) in auto mode
invoke-rc.d: could not determine current runlevel
Setting up sysstat (12.2.0-2) ...

Creating config file /etc/default/sysstat with new version
update-alternatives: using /usr/bin/sar.sysstat to provide /usr/bin/sar (sar) in auto mode
Created symlink /etc/systemd/system/multi-user.target.wants/sysstat.service → /lib/systemd/system/sysstat.service.
Setting up postgresql (12+214ubuntu0.1) ...
Processing triggers for systemd (245.4-4ubuntu3.3) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for libc-bin (2.31-0ubuntu9.1) ...

启动已安装的PostgreSQL。

$ sudo /etc/init.d/postgresql start
 * Starting PostgreSQL 12 database server

将Ubuntu用户切换到Postgres。

$ sudo -u postgres -i
Welcome to Ubuntu 20.04.1 LTS (GNU/Linux 4.19.128-microsoft-standard x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Mon Jan  4 11:17:45 JST 2021

  System load:  0.0                Processes:             26
  Usage of /:   1.0% of 250.98GB   Users logged in:       0
  Memory usage: 3%                 IPv4 address for eth0: 172.30.98.8
  Swap usage:   0%


0 updates can be installed immediately.
0 of these updates are security updates.



This message is shown once a day. To disable it please create the
/var/lib/postgresql/.hushlogin file.
$ whoami
postgres
$ pwd
/var/lib/postgresql