我可以通过执行这条语句来解决这个问题

sudo dpkg-reconfigure mysql-server-5.5

这将改变根密码。

虽然上面的答案(使用mysqladmin)在macOS v10.15 (Catalina)上有效，但在Ubuntu上无效。然后我尝试了许多其他的选项，包括MySQL的安全启动，但都不起作用。

下面是一个例子:

至少在这个版本中，我得到了5.7.28-0ubuntu0.18.04.4的答案缺少IDENTIFIED WITH mysql_native_password。5.7.28是当前LTS的默认设置，因此应该是大多数新系统的默认设置(直到Ubuntu 20.04 (Focal Fossa) LTS问世)。

我发现不能设置root密码MySQL服务器，现在应用

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'your_pass_here';

这是可行的。

当您的密码丢失时就会发生这种情况。

忘记密码时的修改步骤:

Stop MySQL Server (on Linux): sudo systemctl stop mysql Start the database without loading the grant tables or enabling networking: sudo mysqld_safe --skip-grant-tables --skip-networking & The ampersand at the end of this command will make this process run in the background, so you can continue to use your terminal and run mysql -u root (as root). It will not ask for a password. If you get error like as below: 2018-02-12T08:57:39.826071Z mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists. mysql -u root ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) [1]+ Exit 1 Make MySQL service directory. sudo mkdir /var/run/mysqld Give MySQL user permission to write to the service directory. sudo chown mysql: /var/run/mysqld Run the same command in step 2 to run MySQL in background. Run mysql -u root. You will get the MySQL console without entering a password. Run these commands FLUSH PRIVILEGES; For MySQL 5.7.6 and newer ALTER USER 'root'@'localhost' IDENTIFIED BY 'new_password'; For MySQL 5.7.5 and older SET PASSWORD FOR 'root'@'localhost' = PASSWORD('new_password'); If the ALTER USER command doesn't work use: UPDATE mysql.user SET authentication_string = PASSWORD('new_password') WHERE User = 'root' AND Host = 'localhost'; Now exit To stop the instance started manually: sudo kill `cat /var/run/mysqld/mysqld.pid` Restart MySQL sudo systemctl start mysql

注意:对于MySQL 5.7+，请参见Lahiru对这个问题的回答。这包含了更多的最新信息。

对于MySQL < 5.7:

默认root密码为空(即空字符串)，而不是root。所以你可以登录为:

mysql -u root

安装完成后，您显然应该更改root密码:

mysqladmin -u root password [newpassword]

在大多数情况下，您还应该在广泛使用数据库之前设置个人用户帐户。

如果问题仍然存在，请尝试强制修改密码:

/etc/init.d/mysql stop

mysqld_safe --skip-grant-tables &

mysql -u root

设置新的MySQL root用户密码:

use mysql;
update user set password=PASSWORD("NEW-ROOT-PASSWORD") where User='root';
flush privileges;
quit;

停止MySQL服务器:

/etc/init.d/mysql stop

启动MySQL服务器并测试它:

mysql -u root -p

在Ubuntu 16.04 (Xenial Xerus)和MySQL 5.7.13版本中，我能够通过以下步骤解决这个问题:

Follow the instructions from section B.5.3.2.2 Resetting the Root Password: Unix and Unix-Like Systems MySQL 5.7 reference manual When I tried #sudo mysqld_safe --init-file=/home/me/mysql-init & it failed. The error was in /var/log/mysql/error.log: 2016-08-10T11:41:20.421946Z 0 [Note] Execution of init_file '/home/me/mysql/mysql-init' started. 2016-08-10T11:41:20.422070Z 0 [ERROR] /usr/sbin/mysqld: File '/home/me/mysql/mysql-init' not found (Errcode: 13 - Permission denied) 2016-08-10T11:41:20.422096Z 0 [ERROR] Aborting

mysql-init的文件权限不是问题。我们需要编辑AppArmor权限。

Edit by sudo vi /etc/apparmor.d/usr.sbin.mysqld .... /var/log/mysql/ r, /var/log/mysql/** rw, # Allow user init file /home/pranab/mysql/* r, # Site-specific additions and overrides. See local/README for details. #include <local/usr.sbin.mysqld> } Do sudo /etc/init.d/apparmor reload Start mysqld_safe again. Try step 2 above. Check file /var/log/mysql/error.log. Make sure there is no error and the mysqld is successfully started. Run mysql -u root -p Enter password: Enter the password that you specified in mysql-init. You should be able to log in as root now. Shutdown mysqld_safe by sudo mysqladmin -u root -p shutdown Start mysqld the normal way by sudo systemctl start mysql