nginx を入れて、サービスの入口を公開する

grep -nE 'listen .*80 default_server;' /etc/nginx/sites-available/default

22:	listen 80 default_server;
23:	listen [::]:80 default_server;

sudo nginx -t
sudo cp /etc/nginx/sites-available/default /tmp/ch1-nginx-default.before
sudo sed -i 's/listen 80 default_server;/listen 8080 default_server;/' /etc/nginx/sites-available/default
sudo nginx -t
sudo systemctl reload nginx

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

curl --fail --show-error --include http://127.0.0.1/

HTTP/1.1 200 OK
Server: nginx/1.24.0 (Ubuntu)
Date: Sun, 16 Aug 2026 03:53:06 GMT
Content-Type: text/html
Content-Length: 615
Last-Modified: Sun, 16 Aug 2026 03:52:38 GMT
Connection: keep-alive
ETag: "6a813406-267"
Accept-Ranges: bytes

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

sudo ss -lntp | grep nginx

LISTEN 0      511          0.0.0.0:80        0.0.0.0:*    users:(("nginx",pid=1667,fd=5))
LISTEN 0      511          0.0.0.0:8080      0.0.0.0:*    users:(("nginx",pid=1973,fd=11),("nginx",pid=1664,fd=11))
LISTEN 0      511             [::]:80           [::]:*    users:(("nginx",pid=1973,fd=6),("nginx",pid=1667,fd=6),("nginx",pid=1664,fd=6))

sudo sed -i 's/listen \[::\]:80 default_server;/listen [::]:8080 default_server;/' /etc/nginx/sites-available/default
sudo nginx -t
sudo systemctl reload nginx
sudo ss -lntp | grep nginx
curl --fail --show-error http://127.0.0.1/

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
LISTEN 0      511          0.0.0.0:8080      0.0.0.0:*    users:(("nginx",pid=1988,fd=11),("nginx",pid=1664,fd=11))
LISTEN 0      511             [::]:8080         [::]:*    users:(("nginx",pid=1988,fd=13),("nginx",pid=1664,fd=13))

curl: (7) Failed to connect to 127.0.0.1 port 80 after 0 ms: Couldn't connect to server

sudo cp /tmp/ch1-nginx-default.before /etc/nginx/sites-available/default
sudo nginx -t
sudo systemctl reload nginx
systemctl status nginx --no-pager
curl --fail --show-error http://127.0.0.1/
sudo ss -lntp | grep nginx
sudo rm /tmp/ch1-nginx-default.before

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
● nginx.service - A high performance web server and a reverse proxy server
     Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; preset: enabled)
     Active: active (running) since Sun 2026-08-16 03:52:39 UTC; 30s ago
       Docs: man:nginx(8)
    Process: 1636 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
    Process: 1638 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
    Process: 1999 ExecReload=/usr/sbin/nginx -g daemon on; master_process on; -s reload (code=exited, status=0/SUCCESS)
   Main PID: 1664 (nginx)
      Tasks: 3 (limit: 2315)
     Memory: 2.7M (peak: 3.9M)
        CPU: 29ms
     CGroup: /system.slice/nginx.service
             ├─1664 "nginx: master process /usr/sbin/nginx -g daemon on; master_process on;"
             ├─1988 "nginx: worker process"
             └─2000 "nginx: worker process"

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
LISTEN 0      511          0.0.0.0:80        0.0.0.0:*    users:(("nginx",pid=2000,fd=7),("nginx",pid=1664,fd=7))
LISTEN 0      511          0.0.0.0:8080      0.0.0.0:*    users:(("nginx",pid=1988,fd=11))
LISTEN 0      511             [::]:80           [::]:*    users:(("nginx",pid=2000,fd=8),("nginx",pid=1664,fd=8))
LISTEN 0      511             [::]:8080         [::]:*    users:(("nginx",pid=1988,fd=13))

sudo DEBIAN_FRONTEND=noninteractive apt purge -y nginx nginx-common
sudo rm -rf /etc/apt/sources.list.d.part4
sudo rm -f /etc/apt/keyrings/infra-study-archive-keyring.asc
rm -f /tmp/infra-study-archive-keyring.asc

sudo find /etc /var/lib /srv /opt /usr/local "$HOME" \
  -not -path '/var/lib/apt/*' \
  -not -path '/var/lib/dpkg/*' \
  -not -path '/var/lib/systemd/*' \
  -not -path '/var/log/*' \
  -not -path '/var/cache/*' \
  -not -name '.bash_history' \
  -not -path '/etc/passwd-' -not -path '/etc/group-' \
  -not -path '/etc/shadow-' -not -path '/etc/gshadow-' \
  -not -path '/var/lib/fwupd' -not -path '/var/lib/fwupd/*' \
  -not -path '/etc/fwupd' -not -path '/etc/fwupd/*' \
  -not -path '/var/lib/ucf' -not -path '/var/lib/ucf/*' \
  -not -path '/var/lib/landscape' -not -path '/var/lib/landscape/*' \
  -not -path '/etc/ld.so.cache' \
  -not -path '/var/lib/ubuntu-release-upgrader/release-upgrade-available' \
  -not -path '/var/lib/snapd/state.json' \
  -not -path '/var/lib/snapd/maintenance.json' \
  -not -path '/var/lib/logrotate/status' \
  -printf '%p\t%y\t%m\t%U\t%G\t%s\t%T@\n' 2>/dev/null \
  | LC_ALL=C sort \
  | sudo tee /tmp/part4-manifest-after.tsv >/dev/null
sudo diff -u /tmp/part4-manifest-before.tsv /tmp/part4-manifest-after.tsv > /var/tmp/part4-chapter-manifest.diff
diff_rc=$?
if [ "$diff_rc" -le 1 ]; then
  if awk 'BEGIN { FS = "\t"; c = "LC_ALL=C sort" }
      /^\+\+\+|^---|^@@/ { next }
      /^[+-]/ {
        if (NF != 7) { printf "manifest の列数が 7 ではありません: %s\n", $0 > "/dev/stderr"; bad = 1; exit 2 }
        t++; s = substr($1, 1, 1); p = substr($1, 2)
        k = $2 " " $3 " " $4 " " $5 " " ($2 == "d" ? "-" : $6)
        if (s == "-") { if (p in b) { dup = p; exit 2 } b[p] = k; bm[p] = $7; bt[p] = $2 }
        else          { if (p in a) { dup = p; exit 2 } a[p] = k; am[p] = $7 }
      }
      END {
        if (bad) exit 2
        if (dup != "") { printf "同じパスが重複しています: %s\n", dup > "/dev/stderr"; exit 2 }
        print "== 残留候補（0 件で合格）=="
        n = 0
        for (p in b) {
          if (!(p in a)) { print "消えた   " p | c; n++ }
          else if (a[p] != b[p]) { print "変わった " p "  (" b[p] " -> " a[p] ")" | c; n++ }
        }
        for (p in a) if (!(p in b)) { print "増えた   " p | c; n++ }
        fflush(); close(c)
        print "残留候補: " n " 件"
        print "== 更新日時だけ変わった通常ファイル（1 件ずつ理由を説明できること）=="
        m = 0; d = 0
        for (p in b) if ((p in a) && a[p] == b[p] && am[p] != bm[p]) { if (bt[p] == "d") d++; else { print p | c; m++ } }
        fflush(); close(c)
        print "更新日時だけ変わった通常ファイル: " m " 件 ／ ディレクトリ: " d " 件"
        print "差分行総数: " (t + 0)
      }' /var/tmp/part4-chapter-manifest.diff; then
    sudo rm -f /tmp/part4-manifest-before.tsv /tmp/part4-manifest-after.tsv
  else
    echo "差分の表示に失敗しました。構築前・章末の manifest と /var/tmp/part4-chapter-manifest.diff は残してあります。表示された理由を確認してください" >&2
  fi
else
  echo "差分を採れませんでした（diff の終了コード $diff_rc）。構築前 manifest /tmp/part4-manifest-before.tsv があるか確認してください" >&2
fi

sudo rm -f /var/tmp/part4-chapter-manifest.diff
test ! -e /var/tmp/part4-chapter-manifest.diff

（形の例です。M・K・T には実行したときの件数が入ります。更新日時だけ変わった通常ファイルの行と件数は、台・章によって変わります。合格の条件は「残留候補: 0 件」です）
== 残留候補（0 件で合格）==
残留候補: 0 件
== 更新日時だけ変わった通常ファイル（1 件ずつ理由を説明できること）==
（該当するパスが 1 行ずつ並びます）
更新日時だけ変わった通常ファイル: M 件 ／ ディレクトリ: K 件
差分行総数: T

if dpkg-query -W -f='${db:Status-Abbrev}\t${binary:Package}\n' nginx nginx-common 2>/dev/null | grep -q '^ii'; then
  echo "対象 package が残っています"
else
  echo "対象 package なし"
fi
if systemctl is-active --quiet nginx; then
  echo "nginx service 稼働中"
else
  echo "nginx service は非稼働"
fi
if sudo ss -lntp | grep -q ':80 '; then
  echo "80 番の待受あり"
else
  echo "80 番の待受なし"
fi
nginx_paths=(/etc/nginx /etc/default/nginx /etc/init.d/nginx /etc/logrotate.d/nginx)
nginx_path_left=0
for path in "${nginx_paths[@]}"; do
  if sudo test -e "$path"; then
    echo "残留 path: $path"
    nginx_path_left=1
  fi
done
[ "$nginx_path_left" -eq 0 ] && echo "nginx 設定 path なし"
test ! -e /etc/apt/sources.list.d.part4
test ! -e /etc/apt/keyrings/infra-study-archive-keyring.asc
test ! -e /tmp/infra-study-archive-keyring.asc

対象 package なし
nginx service は非稼働
80 番の待受なし
nginx 設定 path なし