GitHub Actions · Ubuntu 26.04 · Checked November 4, 2026

unrecognized configuration parameter "transaction_timeout": pg_dump 18 on Ubuntu 26.04

ubuntu-latest is moving from Ubuntu 24.04 to 26.04 between October 19 and November 19, 2026 (what else changes). The runner image's PostgreSQL goes from 16.15 to 18.6 (the image readmes), and apt-get install postgresql-client now gives PostgreSQL 18 too (18+290ubuntu1). So pg_dump, pg_restore and psql in your steps are 18, while a postgres:16 service container is still 16.

What it looks like

psql:dump.sql:13: ERROR:  unrecognized configuration parameter "transaction_timeout"

pg_dump 17 and later write SET transaction_timeout = 0; near the top of every dump. The setting exists only since PostgreSQL 17 (PostgreSQL 17 documentation), so loading the dump into a 16 or older server fails on that line. With ON_ERROR_STOP or --single-transaction the whole restore stops there. The SQL that pg_restore 18 writes from a custom-format dump has the same line.

The other direction shows up on jobs that still land on 24.04, or that pin it, against a 17 or 18 server:

pg_dump: error: aborting because of server version mismatch
pg_dump: detail: server version: 17.6; pg_dump version: 16.15 (Ubuntu 16.15-1.pgdg24.04+2)

Where the reports came from

• A dump-and-reload check with a postgis/postgis:16-3.5 service and postgresql-client from the runner's apt failed in several projects that share that workflow, in the same week (open-zaak #2616, referentielijsten #188, open-product #386).
• A backup-and-restore drill against a postgres:16-alpine service: the backup passed and the restore failed (evolith #35).
• The version mismatch, on 24.04: installing postgresql-client-17 did not help, because pg_dump still ran the image's 16 (RESIDIO #954).

Fix: dump with the server's own pg_dump

- run: docker exec ${{ job.services.postgres.id }} pg_dump -U postgres app > dump.sql

The service container has the pg_dump that matches its server, so the dump fits the server whatever the runner image is. job.services.<id>.id is the container ID GitHub gives each service. Restore the same way, with docker exec -i ... psql.

Or match the service to the client

Moving the service to PostgreSQL 17 or later makes a pg_dump 18 file load cleanly. One of the projects above went to postgis/postgis:17-3.5 (open-klant 4d312dde). Until November 19, though, the same job can land on 24.04, where pg_dump 16 refuses a 17 server. Either pin the job with runs-on: ubuntu-26.04, or use the docker exec form, which works on both.

Or install the client version you need

The image installs PostgreSQL from the PostgreSQL apt repository and then removes that repository, so postgresql-client-16 is not available until you add it back (resolute-pgdg exists for 26.04). After installing, call the versioned binary rather than plain pg_dump, which can still run the image's own version (RESIDIO's job installed 17 and got 16).

/usr/lib/postgresql/16/bin/pg_dump -h localhost -U postgres app > dump.sql

Pinning the job to runs-on: ubuntu-24.04 also brings back client 16, until GitHub retires that image.

Deleting the SET transaction_timeout line with sed gets past this one line, but a restore drill then no longer tests what a real restore would do, and later versions may add other settings.

Telling it apart

• pg_dump --version prints 18.x on 26.04 and 16.x on 24.04. Print it in the job so the log says which one ran.
• Look at "Set up job": the Runner Image group shows the image. Until November 19 a re-run can land on the other image, so a green re-run proves nothing.

Other 26.04 failures

• Docker-in-Docker on Ubuntu 26.04: the legacy iptables modules are not loaded, so a dockerd inside a container that uses iptables-legacy, such as the dev container docker-in-docker feature :2 or :3, fails with "can't initialize iptables table `nat'"; move the feature to :4 or load the modules on the runner.
• "Error: write EINVAL" from every WebdriverIO worker on Ubuntu 26.04: v9 starts workers through xvfb-run, and the 26.04 one does not pass on the IPC channel; fixed in 9.33.1, which npm's latest tag does not point to yet.
• Postgres never starts in Docker on Ubuntu 26.04: newer kernels such as 7.0.0-42 run container processes as docker-default//&unconfined, so they cannot signal each other and gosu hangs at 100% CPU; reported on self-hosted runners so far.
• "version `GLIBC_2.43' not found" after building on Ubuntu 26.04: glibc is 2.43, so binaries built there can need GLIBC_2.42 or GLIBC_2.43 and fail to start on Ubuntu 24.04, Debian 13 and older; build releases on an older image and check the floor in CI.
• apt on Ubuntu 26.04: renamed and removed packages.
• "coreutils: unknown program": most core tools are uutils.

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