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6.7. Atualizando de uma Versão Estável para a Próxima

Uma das funcionalidades mais conhecidas do Debian é sua habilidade de atualizar um sistema instalado de uma versão estável para a próxima: dist-upgrade — um termo bem conhecido — tem contribuído amplamente para a reputação do projeto. Com algumas poucas precauções, atualizar um computador pode levar alguns minutos, ou algumas dezenas de minutos, dependendo da velocidade de download do repositório de pacotes.

6.7.1. Procedimento Recomendado

Como o Debian tem bastante tempo para evoluir entre lançamentos da versão estável, você deve ler as notas de lançamento ("release notes") antes de atualizar.
In this section, we will focus on upgrading a Stretch system to Buster. This is a major operation on a system; as such, it is never 100% risk-free, and should not be attempted before all important data has been backed up.
Outro hábito que mantém a atualização mais fácil (e rápida) é organizar a quantidade de pacotes instalados e manter apenas aqueles que são realmente necessários. Ferramentas úteis para isto incluem aptitude, deborphan e debfoster (veja Seção 6.2.7, “Rastreando Pacotes Instalados Automaticamente”). Por exemplo, você pode usar o seguinte comando: e, em seguida, usar o modo interativo do aptitude para checar e ajustar as remoções programadas:
# deborphan | xargs aptitude --schedule-only remove
Now for the upgrading itself. First, you need to change the /etc/apt/sources.list file to tell APT to get its packages from Buster instead of Stretch. If the file only contains references to Stable rather than explicit codenames, the change isn't even required, since Stable always refers to the latest released version of Debian. In both cases, the database of available packages must be refreshed (with the apt update command or the refresh button in synaptic).
Uma vez que estas novas fontes de pacotes for cadastrado, você deve primeiro fazer uma atualização mínima com apt upgrade. Ao fazer a atualização em duas etapas, nos facilita o trabalho das ferramentas de gerenciamento de pacotes e muitas vezes garante que temos as versões mais recentes das pessoas, o que pode ter acumulado correções de bugs e melhorias necessárias para concluir a atualização completa da distribuição.
Once this first upgrade is done, it is time to handle the upgrade itself, either with apt full-upgrade, aptitude, or synaptic. You should carefully check the suggested actions before applying them: you might want to add suggested packages or deselect packages which are only recommended and known not to be useful. In any case, the front-end should come up with a scenario ending in a coherent and up-to-date Buster system. Then, all you need is to do is wait while the required packages are downloaded, answer the debconf questions and possibly those about locally modified configuration files, and sit back while APT does its magic.

6.7.2. Lidando com Problemas após uma Atualização

Apesar dos esforços dos mantenedores Debian, uma atualização geral do sistema não é sempre tão suave quando você gostaria. Novas versões de software podem ser incompatíveis com versões anteriores (por exemplo, seu comportamento padrão ou seu formato de dados pode ter mudado). Além disso, alguns bugs podem passam despercebidos apesar da fase de testes pela qual o lançamento do Debian sempre passa.
Para antecipar alguns destes problemas, você pode instalar o pacote apt-listchanges, que mostra informações sobre possíveis problemas no início de uma atualização de pacotes. Esta informação é compilada pelos mantenedores de pacote e colocada em arquivos /usr/share/doc/package/NEWS.Debian para os usuários usarem. A leitura destes arquivos (possivelmente através do apt-listchanges) pode evitar surpresas desagradáveis.
You might sometimes find that the new version of a software doesn't work at all. This generally happens if the application isn't particularly popular and hasn't been tested enough; a last-minute update can also introduce regressions which are only found after the stable release. In both cases, the first thing to do is to have a look at the bug tracking system at https://bugs.debian.org/package, and check whether the problem has already been reported. If this is case it will be also listed before the upgrade begins, if you have apt-listbugs installed. If it hasn't, you should report it yourself with reportbug. If it is already known, the bug report and the associated messages are usually an excellent source of information related to the bug:
  • algumas vezes um patch já existe, e está disponível no bug report; você pode recompilar uma versão consertada de um pacote quebrado localmente (see Seção 15.1, “Reconstruindo um Pacote a partir de suas Fontes”);
  • Em outros casos, os usuários podem encontrar uma gambiarra para o problema e compartilhar suas ideias nas respostas do bug report;
  • em outros casos, um pacote consertado já pode ter sido preparado e publicado pelo mantenedor.
Depending on the severity of the bug, a new version of the package may be prepared specifically for a new revision of the stable release. When this happens, the fixed package is made available in the proposed-updates section of the Debian mirrors (see Seção 6.1.2.3, “Atualizações Propostas”). The corresponding entry can then be temporarily added to the sources.list file, and updated packages can be installed with apt or aptitude.
Sometimes the fixed package isn't available in this section yet because it is pending a validation by the Stable Release Managers. You can verify if that is the case on their web page. Packages listed there aren't available yet, but at least you know that the publication process is ongoing.

6.7.3. Cleaning Up after an Upgrade

APT usually ensures a clean upgrade, pulling in new and updated dependencies, or removing conflicting packages. But even being such a great tool, it cannot cover all tasks users and administrators will face after an upgrade, because they require a human decision.

6.7.3.1. Packages removed from the Debian Archive

Sometimes the Debian FTP Masters remove packages from the Debian archive, because they contain release critical bugs, were abandoned by their upstream author or their package maintainer, or simply reached their end of life. In this case a newer Debian release does not ship the package anymore. To find all packages, which do not have a package source, use the apt-show-versions command:
$ apt-show-versions | grep "No available version"
A similar result can be achieved by aptitude search ~o. If the packages found are not required anymore, they should be purged from the system, because they will not face any updates for critical or security related bugs anymore.

6.7.3.2. Dummy and Transitional Packages

Sometimes, it might be necessary for a package to get a new name. In this case often the old package is kept as an (almost) empty package, depending on the new one and installing only the mandatory files in /usr/share/doc/package/. Such packages are called "dummy" or "transitional" packages. If the package maintainer in charge also changed the section of this package to oldlibs, then tools like aptitude, deboprhan, or debfoster (see sidebar ALTERNATIVA deborphan e debfoster) can pickup these packages to suggest their removal.
Unfortunately there is currently no foolproof way of making sure that these packages are automatically removed or picked by the tools mentioned above. One way to check if the system still has some of these packages installed, is to look through the package descriptions of installed packages and then check the results. Be careful not to schedule the results for automatic removal, because this method can lead to false positives:
$ dpkg -l | grep ^ii | grep -i -E "(transition|dummy)"
Because the new package is pulled in as a dependency of the transitional package, it is usually marked as automatically installed and might be scheduled for removal if you try to purge the transitional package from your system. In this case you can use either of the approaches described in sidebar DICA Removendo e instalando ao mesmo tempo and Seção 6.2.7, “Rastreando Pacotes Instalados Automaticamente” to selectively remove the transitional package.

6.7.3.3. Old or Unused Configuration Files

If the upgrade was successful there might be some configuration file cruft, either from dpkg (see Seção 5.2.3, “Checksums, Lista de arquivos de configuração”), ucf or from removed packages. The latter can be purged by using apt autoremove --purge. The configuration files, that were handled by dpkg or ucf during the upgrade process, have left some counterparts with a dedicated suffix (e.g. .dpkg-dist, .dpkg-old, .ucf-old). Using the find or locate command can help to track them down. If they are no longer of any use, they can be deleted.

6.7.3.4. Files not owned by any Package

The Debian policy enforces that packages don't leave files behind when they are purged. Violating this principle is a serious bug and you will rarely encounter it. If you do, report it; and if you are curious though, you can use the cruft or cruft-ng package to check your system for files not owned by any package.