mysql-server-5.7.postinst is influenced by ~/.my.cnf, causing installation hangs

[Robie Basak]

Related bug: bug 1567696. This bug is to track that we are influenced by ~/.my.cnf, not specifically $HOME.

mysql-server-5.7 version: 5.7.11-0ubuntu4

Steps to reproduce:

sudo -i

Ensure $HOME is /root

cat > ~/.my.cnf <<EOT
[client]
user = root
password = foo
EOT

sudo apt-get install -y mysql-server-5.7

Every time (three times) it prompts for a root password, just press Enter (ie.
set a blank password).

Expected behaviour: apt-get finishes.

Actual behaviour:

mysql-server-5.7.postinst hangs on:

update-alternatives: using /etc/mysql/mysql.cnf to provide /etc/mysql/my.cnf (my.cnf) in auto mode

/var/log/mysql/error.log reports:

2016-04-07T23:12:37.299093Z 0 [Note] Execution of init_file '/var/lib/mysql-files/tmp.LTuPIaNrV0' started.
2016-04-07T23:12:37.299499Z 1 [ERROR] 1524 Plugin 'auth_socket' is not loaded
2016-04-07T23:12:37.299577Z 0 [Note] Execution of init_file '/var/lib/mysql-files/tmp.LTuPIaNrV0' ended.
2016-04-07T23:12:37.299631Z 0 [Note] mysqld: ready for connections.
Version: '5.7.11-0ubuntu5' socket: '/tmp/tmp.FFBBqKBiRF/mysqld.sock' port: 3306 (Ubuntu)

Workaround:

Delete or rename away ~root/.my.cnf.

[Robie Basak (racb)]

This was fixed in 5.7.11-0ubuntu6.