Início / unix / Perguntas / 690203
Accepted
pkaramol
Asked: 2022-02-12 03:06:28 +0800 CST

Faça o serviço systemd entender a mudança no arquivo de configuração

  • 772

Eu tenho um systemdserviço que é mais ou menos assim:

[Service]
ExecStart=/usr/local/bin/binary subcommand
User=my-user
Group=my-group
EnvironmentFile=/etc/my-service/config

Estou alterando o conteúdo de/etc/my-service/config

Devo executar daemon-reloadou apenas recarregar o serviço?

Observe que não tenho uma ExecReloaddiretiva no meu arquivo de unidade; isso afeta o systemctl reload my-servicecomportamento do 's?

systemd

1 respostas

  1. Best Answer

    Nem daemon-reloadnem reloadfará com EnvironmentFile=que seja lido pelo seu processo principal.

    A página man diz que os arquivos listados com EnvironmentFile=serão lidos pouco antes de o processo ser executado.

    • Isso sugere startou restartfará com que o arquivo seja lido. Isso porque startou restartvai executar o processo.
    • Isso também sugere daemon-reloadque não terá nenhum efeito porque daemon-reloadnão startou restarta unidade.
    • Isso também sugere reloadque não terá efeito porque reloadnão cria o processo principal. Apenas dá a oportunidade de enviar um sinal ao processo principal para recarregar sua configuração. Isso é especialmente verdadeiro se você não tiver ExecReload=definido.

    Um experimento de apoio

    $ systemctl --user cat env.service
# /home/stew/.config/systemd/user/env.service
[Service]
ExecStart=/bin/bash -c "while true; do sleep 1; echo $EXAMPLE_ENV; done"
EnvironmentFile=%h/env

$ cat ~/env
EXAMPLE_ENV="Hi"

$ systemctl --user start env.service

    Então eu monitoro o diário durante as operações:

    $ journalctl --user -u env.service -f
...
Feb 11 15:35:47 stewbian systemd[1108]: Started env.service.
Feb 11 15:35:48 stewbian bash[911848]: Hi
Feb 11 15:35:49 stewbian bash[911848]: Hi

    Então eu mudo o arquivo de ambiente e não vejo nenhuma mudança na saída

    $ sed -i -e 's/Hi/Yo/' ~/env
...
Feb 11 15:37:13 stewbian bash[911848]: Hi
Feb 11 15:37:14 stewbian bash[911848]: Hi
Feb 11 15:37:15 stewbian bash[911848]: Hi

    Então eu tento a systemctl reloade não vejo nenhuma mudança na saída:

    $ systemctl --user reload env.service
Failed to reload env.service: Job type reload is not applicable for unit env.service.
...
Feb 11 15:38:14 stewbian bash[911848]: Hi
Feb 11 15:38:15 stewbian bash[911848]: Hi

    Então eu tento a daemon-reloade não vejo nenhuma mudança na saída:

    $ systemctl --user daemon-reload
...
Feb 11 15:38:46 stewbian bash[911848]: Hi
Feb 11 15:38:47 stewbian bash[911848]: Hi

    Então eu tento reiniciar e ver a mudança.

    $ systemctl --user restart env.service
...
Feb 11 15:39:29 stewbian bash[911848]: Hi
Feb 11 15:39:30 stewbian bash[911848]: Hi
Feb 11 15:39:30 stewbian systemd[1108]: Stopping env.service...
Feb 11 15:39:30 stewbian systemd[1108]: Stopped env.service.
Feb 11 15:39:30 stewbian systemd[1108]: Started env.service.
Feb 11 15:39:31 stewbian bash[912531]: Yo
Feb 11 15:39:32 stewbian bash[912531]: Yo

    Uma coisa interessante é adicionar ExecReload=/bin/bash -c 'echo $EXAMPLE_ENVà unidade. Nesse caso eu recebo isso:

    Feb 11 15:58:24 stewbian bash[914611]: Hi
Feb 11 15:58:25 stewbian bash[914611]: Hi
Feb 11 15:58:26 stewbian systemd[1108]: Reloading env.service...
Feb 11 15:58:26 stewbian bash[914640]: Yo
Feb 11 15:58:26 stewbian systemd[1108]: Reloaded env.service.
Feb 11 15:58:26 stewbian bash[914611]: Hi
Feb 11 15:58:27 stewbian bash[914611]: Hi

    Então aqui você pode ver systemdque lê EnvironmentFile=antes de iniciar o ExecReload=, mas só passa o novo ambiente para o novo processo. Não altera o ambiente dos processos existentes.

    Tentei novamente colocando essas bashcoisas em um script separado para garantir que a substituição da variável de ambiente do systemd não afetasse nada durante a análise das Exec*=linhas... Mesmo resultado.

    Documentação de suporte

    man systemd.exec:

    EnvironmentFile=
   ...         
   The files listed with this directive will be read shortly before
   the process is executed (more specifically, after all processes
   from a previous unit state terminated. This means you can
   generate these files in one unit state, and read it with this
   option in the next. The files are read from the file system of
   the service manager, before any file system changes like bind
   mounts take place).

    man systemctl:

       reload PATTERN...
       Asks all units listed on the command line to reload their
       configuration. Note that this will reload the service-specific
       configuration, not the unit configuration file of systemd. If you
       want systemd to reload the configuration file of a unit, use the
       daemon-reload command. In other words: for the example case of
       Apache, this will reload Apache's httpd.conf in the web server,
       not the apache.service systemd unit file.

       This command should not be confused with the daemon-reload
       command.

   daemon-reload
       Reload the systemd manager configuration. This will rerun all
       generators (see systemd.generator(7)), reload all unit files, and
       recreate the entire dependency tree. While the daemon is being
       reloaded, all sockets systemd listens on behalf of user
       configuration will stay accessible.

       This command should not be confused with the reload command.

       In other words: for the example case of Apache, this will reload Apache's httpd.conf in the
       web server, not the apache.service systemd unit file.

       This command should not be confused with the daemon-reload command.

    man systemd.service:

    ExecReload=
    Commands to execute to trigger a configuration reload in the
    service. This argument takes multiple command lines, following
    the same scheme as described for ExecStart= above. Use of this
    setting is optional. Specifier and environment variable
    substitution is supported here following the same scheme as for
    ExecStart=.

    One additional, special environment variable is set: if known,
    $MAINPID is set to the main process of the daemon, and may be
    used for command lines like the following:

        ExecReload=kill -HUP $MAINPID

    Note however that reloading a daemon by sending a signal (as with
    the example line above) is usually not a good choice, because
    this is an asynchronous operation and hence not suitable to order
    reloads of multiple services against each other. It is strongly
    recommended to set ExecReload= to a command that not only
    triggers a configuration reload of the daemon, but also
    synchronously waits for it to complete. For example, dbus-
    broker(1) uses the following:

        ExecReload=busctl call org.freedesktop.DBus \
               /org/freedesktop/DBus org.freedesktop.DBus \
               ReloadConfig
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