I am testing a backup/restore procedure for my postgres DB inside a docker container.
I dump my db like this:
$ docker exec -ti my_postgres_container pg_dump -Fc -U postgres > db.dump
Afterwards, I try to restore it like this:
$ docker cp db.dump my_postgres_container:/db.dump
$ docker exec -ti my_postgres_container pg_restore -U postgres -c -d postgres db.dump
The command returns without output or errors, but nothing happens.
So instead, I tried to restore it manually like this:
$ docker cp db.dump my_postgres_container:/db.dump
$ docker exec -ti my_postgres_container bash
root@fdaad610bee3:/# pg_restore -U postgres -c -d postgres db.dump
Segmentation fault (core dumped)
Why is pg_restore segfaulting when trying to read my DB dump?
Analysis:
The problem is caused by a corruption when dumping the DB. pg_dump
produces binary output. This output is first passed through the Docker container's stdout
and then redirected into a file on the host. Somewhere on the way, non-ASCII bytes are corrupted.
Solution:
Let pg_dump
write to a file inside the Docker container , then copy that out to the host:
correct dumping procedure:
docker exec -ti my_postgres_container bash -c 'pg_dump -Fc -U postgres > /db.dump'
docker cp my_postgres_container:/db.dump db.dump
correct restoring procedure:
docker cp db.dump my_postgres_container:/db.dump
docker exec -ti my_postgres_container pg_restore -U postgres -c -d postgres db.dump
For those like me that have the corrupt dump and can't follow the accepted answer, I found a workaround here
The dump file's format is DOS when you open with vim,
and if you change this to unix (:set ff=unix
) and save it,
the segmentation fault will go away
And that does works.
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