I use steam deck as a workstation. Initially, I needed to install the clang-format for c/c++, but there was a problem with pacman. Below I will provide the errors that I encounter. My system has been translated into Russian, so I will duplicate the translation below the original errors.
The main thing I want to solve is to install the clang-format. Solving the problem with paсman is a secondary task.

Original errors:

sudo pacman -S foobar:
ошибка: не удалось начать транзакцию (не удалось заблокировать базу данных) ошибка: не удалось заблокировать базу: Файловая система доступна только для чтения

sudo pacman -Sy:
:: Обновление баз данных пакетов... ошибка: failed to synchronize all databases (не удалось заблокировать базу данных)

clang-format:
bash: clang-format: команда не найдена

Translated into English:

sudo pacman -S foobar:
error: Failed to start transaction (failed to lock database) error: failed to lock database: File system is read-only

sudo pacman -Sy:
::Updating package databases... error: failed to synchronize all databases (failed to lock the database)

clang-format:
bash: clang-format: command not found

I used similar questions and found several solutions, but none worked for me.

1. It was suggested to delete this file: sudo rm /var/lib/pacman/db.lck. However, I don’t have any paсman file or directory.
2. It was suggested to delete the installation files using the pacman -Scc command.
   It gave the following error:
   error: failed to start transaction (failed to lock the database) error: failed to lock the database: The file system is read-only