attempt to write a readonly database

What this means

SQLITE_READONLY (result code 8) is returned when SQLite attempts a write operation on a database that was opened in read-only mode, or whose underlying file has OS-level read-only permissions. The check is performed before any disk I/O so the database is never partially modified.

Why it happens

1. 1The database file or its containing directory has read-only OS permissions (chmod 444)
2. 2The connection was opened with the SQLITE_OPEN_READONLY flag
3. 3The database is on a read-only filesystem (e.g., CD-ROM, read-only NFS mount)
4. 4The WAL file or shared-memory file exists but is not writable while the database itself is readable

How to reproduce

A database file is made read-only at the OS level and then a write is attempted.

import sqlite3, os, stat

# Create and populate the database
conn = sqlite3.connect('/tmp/demo.db')
conn.execute('CREATE TABLE t (x INTEGER)')
conn.commit()
conn.close()

# Make it read-only
os.chmod('/tmp/demo.db', stat.S_IRUSR | stat.S_IRGRP)

# Attempt to write — triggers SQLITE_READONLY
conn = sqlite3.connect('/tmp/demo.db')
conn.execute('INSERT INTO t VALUES (1)')

Fix 1: Restore write permissions

When the file should be writable but permissions were accidentally changed.

import os, stat
os.chmod('/tmp/demo.db', stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP | stat.S_IWGRP)

Fix 2: Open a copy of the database for writing

When the source database must remain read-only (e.g., shipped with an app).

import sqlite3, shutil

shutil.copy('/assets/readonly.db', '/data/user.db')
conn = sqlite3.connect('/data/user.db')
conn.execute('INSERT INTO t VALUES (1)')
conn.commit()

What not to do

Version notes

Dangerous variant

Sources

Confidence assessment

See also