[Raspberry pi] Ramdiskを設定したら nginx が起動しなくなったので、rc-local で対処する。

以前書いた記事[Ubuntu] Raspberry pi に Ramdiskを設定したら nginx とか MySQL が起動しなくなったので、rc-local で対処する。をラズパイ4でも試してみたというだけの話。今はMySQLはDockerコンテナで動かしているので、今回の対象は /var/log/nginx のみ。

試した環境

Raspberry Pi 4
Ubuntu 20.10 64bit
$ uname -a
Linux pi4 5.8.0-1017-raspi #20-Ubuntu SMP PREEMPT Mon Mar 1 14:19:20 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux

対策

systemdに用意されている /etc/rc.local Compatibility を使う。

最初に/etc/rc.local を準備しておく。

$ sudo vi /etc/rc.local
#!/bin/bash
mkdir -p /var/log/nginx
chown root.www-data /var/log/nginx
exit 0
$ sudo chmod +x /etc/rc.local

systemd の rc.local Compatibility を有効にする。
/lib/systemd/system/rc-local.serviceの一番下に[Install]セクションを追記する。

$ sudo vi /lib/systemd/system/rc-local.service
SPDX-License-Identifier: LGPL-2.1+
 #
 This file is part of systemd.
 #
 systemd is free software; you can redistribute it and/or modify it
 under the terms of the GNU Lesser General Public License as published by
 the Free Software Foundation; either version 2.1 of the License, or
 (at your option) any later version.
 This unit gets pulled automatically into multi-user.target by
 systemd-rc-local-generator if /etc/rc.local is executable.
 [Unit]
 Description=/etc/rc.local Compatibility
 Documentation=man:systemd-rc-local-generator(8)
 ConditionFileIsExecutable=/etc/rc.local
 After=network.target
 [Service]
Type=forking
 ExecStart=/etc/rc.local start
 TimeoutSec=0
 RemainAfterExit=yes
 GuessMainPID=no
 kkitta@pi4:~$ cat /lib/systemd/system/rc-local.service
 SPDX-License-Identifier: LGPL-2.1+
 #
 This file is part of systemd.
 #
 systemd is free software; you can redistribute it and/or modify it
 under the terms of the GNU Lesser General Public License as published by
 the Free Software Foundation; either version 2.1 of the License, or
 (at your option) any later version.
 This unit gets pulled automatically into multi-user.target by
 systemd-rc-local-generator if /etc/rc.local is executable.
 [Unit]
 Description=/etc/rc.local Compatibility
 Documentation=man:systemd-rc-local-generator(8)
 ConditionFileIsExecutable=/etc/rc.local
 After=network.target
 [Service]
 Type=forking
 ExecStart=/etc/rc.local start
 TimeoutSec=0
 RemainAfterExit=yes
 GuessMainPID=no

[Install]
WantedBy=multi-user.target

サービスを有効にする。

$ sudo systemctl enable rc-local
 Created symlink /etc/systemd/system/multi-user.target.wants/rc-local.service → /lib/systemd/system/rc-local.service.

参考：/lib/systemd/system/rc-local.service に [Install] セクションを書いておかないと、下記のエラーが出る。

$ sudo systemctl enable rc-local
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
 Alias= settings in the [Install] section, and DefaultInstance= for template
 units). This means they are not meant to be enabled using systemctl.
 Possible reasons for having this kind of units are:
 • A unit may be statically enabled by being symlinked from another unit's
   .wants/ or .requires/ directory.
 • A unit's purpose may be to act as a helper for some other unit which has
   a requirement dependency on it.
 • A unit may be started when needed via activation (socket, path, timer,
   D-Bus, udev, scripted systemctl call, …).
 • In case of template units, the unit is meant to be enabled with some
   instance name specified.