`docker exec -i db_mysql mysqldump` doesn't produce any backup-CodePudding

I have a MySQL Docker container (db_mysql) with database wp_almond

When I try to dump it with docker exec -i db_mysql mysqldump it doesn't work

$ docker exec -i db_mysql mysqldump -u root -p wp_almond > wp_almond.sql
$ docker exec -i db_mysql ls # Notice that "wp_almond.sql" was not created
bin
boot
dev
docker-entrypoint-initdb.d
entrypoint.sh
etc
home
lib
lib64
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var

But entering the container and then doing the mysqldump inside works

$ docker exec -it db_mysql sh
$ mysqldump -u root -p wp_almond > wp_almond.sql
$ ls # Here "wp_almond.sql" is present
bin
boot
dev
docker-entrypoint-initdb.d
entrypoint.sh
etc
home
lib
lib64
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
wp_almond.sql

I don't know why, I need to do it without entering the container with sh for a backup script

CodePudding user response：

When you run

docker exec -i db_mysql mysqldump -u root -p wp_almond

then the output is produced to stdout (of your host terminal)

Therefore, when you run

docker exec -i db_mysql mysqldump -u root -p wp_almond > wp_almond.sql

It simply redirects the output of your terminal to file on your host itself.

If you want to save it in the container, try this instead

docker exec -i db_mysql sh -c "mysqldump -u root -p wp_almond > wp_almond.sql"