From 6ae35534b7b6e10a26a0f2b2a0e37d7f7cfe47dd Mon Sep 17 00:00:00 2001 From: Ben Radford <104896700+benradf@users.noreply.github.com> Date: Tue, 20 Jun 2023 10:34:09 +0100 Subject: Support opening local store with database on read-only filesystem (#8356) Previously it was not possible to open a local store when its database is on a read-only filesystem. Obviously a store on a read-only filesystem cannot be modified, but it would still be useful to be able to query it. This change adds a new read-only setting to LocalStore. When set to true, Nix will skip operations that fail when the database is on a read-only filesystem (acquiring big-lock, schema migration, etc), and the store database will be opened in immutable mode. Co-authored-by: Ben Radford Co-authored-by: cidkidnix Co-authored-by: Dylan Green <67574902+cidkidnix@users.noreply.github.com> Co-authored-by: John Ericson Co-authored-by: Valentin Gagarin --- src/libstore/local-store.hh | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'src/libstore/local-store.hh') diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh index 70debad38..8a3b0b43f 100644 --- a/src/libstore/local-store.hh +++ b/src/libstore/local-store.hh @@ -46,6 +46,23 @@ struct LocalStoreConfig : virtual LocalFSStoreConfig "require-sigs", "Whether store paths copied into this store should have a trusted signature."}; + Setting readOnly{(StoreConfig*) this, + false, + "read-only", + R"( + Allow this store to be opened when its [database](@docroot@/glossary.md#gloss-nix-database) is on a read-only filesystem. + + Normally Nix will attempt to open the store database in read-write mode, even for querying (when write access is not needed), causing it to fail if the database is on a read-only filesystem. + + Enable read-only mode to disable locking and open the SQLite database with the [`immutable` parameter](https://www.sqlite.org/c3ref/open.html) set. + + > **Warning** + > Do not use this unless the filesystem is read-only. + > + > Using it when the filesystem is writable can cause incorrect query results or corruption errors if the database is changed by another process. + > While the filesystem the database resides on might appear to be read-only, consider whether another user or system might have write access to it. + )"}; + const std::string name() override { return "Local Store"; } std::string doc() override; @@ -269,6 +286,10 @@ public: private: + /** + * Retrieve the current version of the database schema. + * If the database does not exist yet, the version returned will be 0. + */ int getSchema(); void openDB(State & state, bool create); -- cgit v1.2.3