Redis "MISCONF Redis is configured to save RDB snapshots": the persistence failure that turns reads into errors
Problem
A dev Redis container started rejecting every write — and application code that only read was failing too:
MISCONF Redis is configured to save RDB snapshots, but it's currently unable to persist on disk. Commands that may modify the data set are disabled, because of a misconfiguration. Please check Redis logs for details about the error.The surprise is by design: when the BGSAVE child fails, Redis stops accepting writes so its persisted copy cannot silently diverge from memory. Reads that touched the dataset through write-shaped commands also failed.
Root cause
The BGSAVE fork failed, and Redis's log names the exact reason — on containerized dev environments it is almost always one of:
1. Read-only filesystem or missing write permission for /data (the container's default dump dir). 2. Disk full on the host — RDB dumps are size-of-dataset. 3. The notorious macOS Docker case: /data bind-mounted from a path Docker's file sharing cannot fsync reliably, or the VM's disk image being full (see the no-space post in this archive — same root, different error surface).
docker logs redis 2>&1 | grep -i -E "bgsave|permission|disk|error" | tail -5
… 1 more line in the fix🔒 the fix — including 3 code blocks — is members-only. $1/mo unlocks everything.