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Resizing XFS root partition in GCP

How to resize a root partition in GCP.

Increase disk size.

gcloud compute disks resize server-boot-disk-name \
--size=50GB \
--zone us-central1-c \
--project your-project-id

Run growpart.

growpart /dev/sda 1

Run xfs_growfs.

xfs_growfs /dev/sda1

To verify, run these.

lsblk
df -Th

Sudoers File Explained

You are probably wondering how the sudoers file works. Here’s a simple explanation.

Command

username host=(user:group) tag:commands

Explanation

    • username – the specified user allowed to run commands.
    • host – the specified host the command is allowed to run.
    • user – specifies which users can use the command.
    • group – specifies which groups can run the command.
    • tag – the option allowed. NOPASSWD
    • command – the command allowed to run.

Examples

root    ALL=(ALL) ALL
username ALL=(ALL) ALL
john test=(ALL) NOPASSWD: /bin/useradd
jane ALL=(sales) NOPASSWD: /bin/sh
%sudo ALL=(ALL) ALL
%adgroup ALL=(ALL) ALL

Set Immutable Attribute

If you don’t want a file edited or deleted, you can set the immutable attribute to ON. If activated, not even root or the owner of the file can delete it. Users with write access can still read it, but they obviously will not be able to modify it. To unset it, just use the -i option.

# Set immutable attribute
sudo chattr +i text.txt
 
# Unset immutable attribute
sudo chattr -i text.txt

Recover MySQL Root Password

How to recover a MySQL root password without a password.

  1. Stop MySQL.
  2. Start MySQL Safe Mode.
  3. Login to MySQL as root without password.
  4. Change root password.

# Stop MySQL.
service mysql stop
# MySQL Safe Mode.
mysqld_safe --skip-grant-tables &
# Login to MySQL without password. Set new password.
mysql -u root -p
use mysql;
# For MySQL 5.6 or lower
UPDATE mysql.user SET Password=PASSWORD('newpassword') WHERE User='root';
# For MySQL 5.7 or higher
SET PASSWORD FOR 'root'@'localhost' = PASSWORD("newpassword");
FLUSH PRIVILEGES;
exit;
# Kill mysqld
killall mysqld
# Restart MySQL
service mysql start

I ran into issues running MySQL Safe mode. I got a “UNIX socket file don’t exists” error. Here’s the fix.

mkdir -p /var/run/mysqld
chown mysql:mysql /var/run/mysqld

Change MySQL Password

The following are instructions on how to change your MySQL password from the Unix command line.

Login to MySQL and access MySQL table.

mysql -u root -p
use mysql;

Change the password for any user, flush privileges and quit.

update user set password=PASSWORD('new_password') where User='root';
flush privileges;
quit

Make sure to make password changes on your applications as well.

In WordPress, edit the wp-config.php file to change database password.