Read-only: unable to obtain shared lock

SQLITE_READONLY_CANTLOCK (520) is returned when a read-only connection cannot acquire the shared lock needed to start a read transaction, because the shared-lock byte cannot be written (the file is read-only).

1. 1Database file is on a read-only filesystem that does not support the lock byte mechanism.
2. 2Shared-cache mode on a read-only file.

Read-only filesystem mount, certain Docker or Kubernetes volume configurations.

# Mount a database read-only where lock bytes cannot be written
import sqlite3
conn = sqlite3.connect('file:/ro/my.db?mode=ro', uri=True)
conn.execute('SELECT 1')  # May raise SQLITE_READONLY_CANTLOCK

sqlite3.OperationalError: unable to open database file

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