Category: Linux

How to find MySQL root password in Webuzo
Webuzo Hosting control panel stores MySQL root password in the file /var/webuzo/my.conf

To find MySQL root password on the Webuzo server, run the command
```
cat /var/webuzo/my.conf
```
Back to Webuzo
December 27, 2021
Install PHP 5.6 on AlmaLinux 8
To install PHP 5.6 on AlmaLinux 8, first enable the epel repository.
```
dnf install -y epel-release
```
install remi repository with the command
```
dnf install http://rpms.remirepo.net/enterprise/remi-release-8.rpm
```
Now you can install PHP 5.6 with
```
dnf install php56
```
You can execute PHP with the command
```
php56
```
If you want PHP 5.6 to work with the command “php”, then edit
```
vi ~/.bashrc
```
At end of the file, add
```
source /opt/remi/php56/enable
```
Log off and login to the server or run command
‘
```
source /opt/remi/php56/enable
```
Or you can create a symlink
```
ln -s /opt/remi/php56/root/usr/bin/php /usr/bin/php
```
If you need PHP work with Apache, run install Apache with
```
dnf install httpd
```
Install php-fpm with
```
dnf install php56-php-fpm
```
Enable and restart Apache
```
systemctl enable php56-php-fpm
systemctl enable httpd
systemctl restart httpd
systemctl restart php56-php-fpm
```
php-fpm pool config file available at
```
/etc/opt/remi/php56/php-fpm.d/www.conf
```
December 18, 2021
How to find if Log4J is installed in my server
A critical vulnerability (CVE-2021-44228) was identified on the popular log4j logger library used by a lot of popular Java applications. The remote code execution (RCE) vulnerability allows attackers to gain access to the server by getting the application to log a special string.

Apache Log4j versions 2.0-beta9 to 2.14.1 are affected by this critical vulnerability.

To find if Log4J is installed on your server, run
```
find / -type f -name log4j*
```
This will list all available log4j files on your server.

Example
```
root@server:~# find / -type f -name log4j*
/opt/SoapUI-5.4.0/licenses/log4j-LICENSE.txt
/opt/SoapUI-5.4.0/lib/log4j-1.2.14.jar
root@server:~# 
```
In the above result, the server has an application SoapUI-5.4.0, that use Log4J. But the version is older than 2.0, so not affected by this vulnerability.

If your server has any application, that uses Log4J and it uses a vulnerable version, you need to upgrade it to the latest version.

how to check apache log4j version

Usually, the jar file has names like
```
log4j-1.2.14.jar
```
File name format is log4j-VERSION.jar, in this case, version of log4j is 1.2.14
December 17, 2021

How to Install MySQL 5.7 on Oracle Linux 7

Oracle Linux 7 comes with MySQL yum repository pre-installed. By Default MySQL 8 repository is enabled. You can disable MySQL 8 repository and enable MySQL 5.7 repository to install MySQL 5.7.

You can find enabled repositories with command

yum repolist all |  grep -i mysql

Example

[root@sql2 ~]# yum repolist all |  grep -i mysql
ol7_MySQL55/x86_64                      MySQL 5.5 for Oracle Lin disabled
ol7_MySQL56/x86_64                      MySQL 5.6 for Oracle Lin disabled
ol7_MySQL57/x86_64                      MySQL 5.7 for Oracle Lin disabled
ol7_MySQL80/x86_64                      MySQL 8.0 for Oracle Lin enabled:    281
ol7_MySQL80_connectors_community/x86_64 MySQL 8.0 Connectors Com enabled:     56
ol7_MySQL80_tools_community/x86_64      MySQL 8.0 Tools Communit enabled:     15
[root@sql2 ~]#

Let’s disable MySQL 8 repo and enable MySQL 5.7 repository.

yum install -y yum-utils
yum-config-manager --disable ol7_MySQL80 ol7_MySQL80_connectors_community ol7_MySQL80_tools_community
yum-config-manager --enable ol7_MySQL57

Before you can install MySQL 5.7, if your server has any MySQL 8 related packages installed, you need to uninstall them.

On my server, I had the following packages installed.

[root@mysql1 ~]# rpm -qa | grep mysql
mysql-community-client-plugins-8.0.26-1.el7.x86_64
mysql-community-common-8.0.26-1.el7.x86_64
mysql-community-libs-8.0.26-1.el7.x86_64
mysql-release-el7-1.0-5.el7.x86_64
mysql-community-libs-compat-8.0.26-1.el7.x86_64
[root@mysql1 ~]#

These are installed as dependency for the postfix mail server, so if you remove the packages with yum, postfix also get removed, so I removed it with command

rpm -e --nodeps mysql-community-client-plugins-8.0.26-1.el7.x86_64
rpm -e --nodeps mysql-community-common-8.0.26-1.el7.x86_64
rpm -e --nodeps mysql-community-libs-8.0.26-1.el7.x86_64
rpm -e --nodeps mysql-community-libs-compat-8.0.26-1.el7.x86_64

–nodeps option will remove packages without removing dependent packages. Make sure you don’t remove the package mysql-release-el7-1.0-5.

Now you can install MySQL server with command

yum install mysql-community-server

Enable and start MySQL server

systemctl enable mysqld --now

To find MySQL initial password, use

grep 'temporary password' /var/log/mysqld.log

mysql -u root -p

Enter the MySQL server temporary password, then execute the following SQL to change the MySQL root password.

ALTER USER 'root'@'localhost' IDENTIFIED BY 'NEW_MYSQL_ROOT_PW';

NEW_MYSQL_ROOT_PW – replace with your new secure MySQL root password.

You can secure MySQL installation by running

mysql_secure_installation

December 15, 2021

sudo: command not found
On a Debian server, when running a command with sudo, I got the error
```
sudo: command not found
```
To fix this, you need to install “sudo” package. If you are logged in as non-root user, then you need to become root, for this, you can use the command
```
su -
```
Enter the root password when it prompt for the password.

Once logged in as user root, you can install sudo with the command
```
apt install sudo
```
To add a user to sudo group, run the command
```
usermod -aG sudo USER_NAME
```
Or
```
adduser USER_NAME sudo
```
If you don’t have a user, you can create a user with the command
```
useradd -m --shell /bin/bash USER_NAME
```
To verify if the user has sudo rights, you can use the command “sudo -v”. You can also use “id” or “groups” command, which lists all groups the current user is in, you can verify if the user is part of sudo group.
December 14, 2021
Convert image to WebP format in Ubuntu
WebP is an image format for web by Google. The size of webp images are much smaller compared with other image formats, so better to use webp images on websites for faster site load speed.

To install webp on Ubuntu/Debian, run
```
sudo apt install webp
```
To convert an image to webp format, run
```
cwebp image.png -o image.webp
```
With the above command, image.png file gets converted to image.webp

You can specify quality with -q option
```
-q  ............. quality factor (0:small..100:big), default=75
```
To view a webp image, run
```
vwebp image.webp
```
December 13, 2021
bash: /usr/bin/man: No such file or directory
On Ubuntu, I get the following error
```
root@vps1:~# man
bash: /usr/bin/man: No such file or directory
root@vps1:~#
```
This is fixed by installing man with apt-get
```
apt-get install man
```
December 11, 2021
How to Migrate CentOS to Oracle Linux
Oracle Linux is Free 100% binary-compatible with Red Hat Enterprise Linux, same as CentOS. Unlike RHEL, Oracle Linux is free even for commercial use. Oracle only charges if you need support.

Oracle provides a script to convert CentOS to Oracle Linux

https://github.com/oracle/centos2ol

This script support CentOS 6, CentOS 7 and CentOS 8.

Before you can run the convert script, make sure you have updated the system to the latest version with yum or dnf and take a backup in case anything goes wrong.
```
yum update
```
Download update centos2ol script
```
wget https://raw.githubusercontent.com/oracle/centos2ol/main/centos2ol.sh
```
Convert your CentOS installation to Oracle Linux with the command
```
bash centos2ol.sh -V
```
Reboot the server
```
reboot
```
December 11, 2021
How to delete an mdadm RAID Array
Deleting a software RAID array will result in all data stored in the devices being lost. So be careful when you remove a RAID array, take backups in case needed.

Before you can remove the software RAID array, you need to unmount it.
```
umount /dev/mdX
```
Where /dev/mdX is the device name for the RAID device you need to remove.

Find the disk used to create the RAID with the command
```
mdadm --detail /dev/mdX
```
Stop the RAID device with the command
```
mdadm --stop /dev/mdX
```
Now you need to run the following commands for each storage device that are part of the RAID device.
```
mdadm --zero-superblock /dev/sdXY
```
IMPORTANT: you need to run this for each member of the RAID device.

Finally, edit /etc/mdadm/mdadm.conf, and remove the entry for the RAID array.
December 10, 2021
RAID getting created as /dev/md127
When I create software RAID with mdadm, it gets created as /dev/md127, instead of /dev/md0 I specified while creating RAID.

To fix this, you need to add RAID definition in /etc/mdadm/mdadm.conf, this can be done with
```
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
```
Now run command
```
update-initramfs -u
```
Reboot the server, after reboot, RAID device will be named properly.
December 10, 2021
How to disable GUI in Ubuntu
If you have installed Ubuntu with GUI and don’t want GUI, you can disable GUI from starting on boot with command
```
systemctl set-default multi-user
```
If you need to GUI auto-start on boot, run
```
systemctl set-default graphical.target
```
December 9, 2021
How to Setup Software RAID 0 on Linux Server
RAID 0 allows you to combine multiple disks into one large disk. Only use RAID 0 if the data is not important to you, for example, a backup server. If one disk fails in a RAID 0 array, all the data will be lost.

To create a software RAID 0 with 2 or more disks, first, we need to prepare the disks to be used as RAID members. Run the following commands on each of the disks we will be adding to the RAID 0 array.
```
parted /dev/sdX mklabel gpt
parted /dev/sdX mkpart primary ext4 0% 100%
parted /dev/sdX set 1 raid on
```
Replace /dev/sdX with actual device names and run the commands for all devices you will be adding to the RAID 0.

Create RAID 0

To create RAID 0, run the following command
```
mdadm --create --verbose /dev/md0 --raid-devices=2 --level=0 /dev/sdc1 /dev/sdd1
```
In the above command,

–raid-devices=2 = number of disks in the RAID. In this case, we have 2 disks. If you have more than 2 disks, change the number accordingly.

/dev/sdc1 /dev/sdd1 = device names, change it with your actual device names. If you have more devices, add them.

/dev/md0 = raid device name, it can be md0, md1, md2 etc..

Format RAID device

Before you can use RAID device, you need to format it.
```
mkfs.ext4 /dev/mdX
```
Replace /dev/mdX with your actual device name.

Updating mdadm.conf

Run
```
mdadm --detail --scan
```
It will print RAID definitions like the following example
```
root@grml ~ # mdadm --detail --scan
ARRAY /dev/md0 metadata=1.2 name=grml:0 UUID=44f0ec6b:f8311a0c:382295f8:d41fa0fe
root@grml ~ #  
```
You need to edit the file
```
vi /etc/mdadm/mdadm.conf 
```
Add the ARRAY definitions at end of the file. If any definitions are already there, don’t repeat them.

Mounting New RAID Device

Before you can mount RAID device, you need to find UUID for the raid device, this can be done with command
```
blkid
```
Example
```
root@grml ~ # blkid
/dev/loop0: TYPE="squashfs"
/dev/sda2: UUID="feacd62e-d23f-483d-8971-aa3f110fea05" TYPE="swap" PARTUUID="3019f70f-516a-493f-97cf-2aa001e1c574"
/dev/sda3: UUID="f162656d-bde9-4b14-8823-21e2a1618a2d" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="1fd4e63f-33a4-4c52-bc00-915c9d7965b8"
/dev/sda4: UUID="52ceb7c4-f065-4cc7-9c19-276a98be29a8" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="b8f92699-2892-482c-8abe-b90ca91b5fc0"
/dev/sdb1: UUID="44f0ec6b-f831-1a0c-3822-95f8d41fa0fe" UUID_SUB="65fd2c84-1217-2df7-2a2c-83046458805a" LABEL="grml:0" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="b197077b-4a34-4459-8230-5c2a3b1c7085"
/dev/sdc1: UUID="44f0ec6b-f831-1a0c-3822-95f8d41fa0fe" UUID_SUB="fedb9e98-dd9f-daed-fc63-4f6a86ebfc9e" LABEL="grml:0" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="807fda4f-d22b-4fa7-8810-839e68ae917e"
/dev/sdd1: UUID="44f0ec6b-f831-1a0c-3822-95f8d41fa0fe" UUID_SUB="071de57a-6d12-70e8-ed6d-cefe8371e915" LABEL="grml:0" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="76f0cbbe-858a-4153-87dd-5665d1ac9939"
/dev/sda1: PARTUUID="9034a389-a6b2-424e-bd19-ce7e55561eba"
/dev/md0: UUID="9bd3d3ee-cc6b-43d5-91ed-627440cc9154" BLOCK_SIZE="4096" TYPE="ext4"
root@grml ~ # 
```
In this cause UUID for /dev/md0 is
```
UUID="9bd3d3ee-cc6b-43d5-91ed-627440cc9154"
```
Edit /etc/fstab
```
vi /etc/fstab
```
Add
```
UUID="9bd3d3ee-cc6b-43d5-91ed-627440cc9154"   /home  ext4    defaults  0       1
```
In the above

/home = is the mount point. If you need to mount the new RAID device as another folder, you need to create an empty directory first.

UUID=”9bd3d3ee-cc6b-43d5-91ed-627440cc9154″ = replace with your actual UUID.

Check status of raid

To see the status of the RAID, use the command
```
cat /proc/mdstat
```
Find RAID details

To find RAID details, use the following command
```
mdadm --detail /dev/mdX
```
Back to RAID
December 9, 2021

Category: Linux

how to check apache log4j version

Create RAID 0

Format RAID device

Updating mdadm.conf

Mounting New RAID Device

Check status of raid

Find RAID details