Category: How To

How to Update PATH Variable in Linux

A PATH variable is a system variable that stores the information about the binary files location that you may run for commands. When you log in as an user, or use a custom control panel like Plesk/Cyberpanel/Cpanel, you might want to add some custom paths as a user to take binary commands. One of the example, could be to change the default php path, or a laravel command location from vendor folder. To do this, you need to extend/update the PATH variable for a specific user.

PATH variable extends with the “:”. If you type the following, in your shell, you may see the existing paths in the PATH variable:

[elastic-keldysh@pl1 ~]$ echo $PATH
/usr/share/Modules/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin

Now, if I want to extend this to take the php binary available in /opt/plesk/php/7.2/bin/php, then we can extend the PATH variable using the following:

PATH=$PATH:/opt/plesk/php/7.2/bin/

Now, if you check, the PATH variable again, you can see it is added:

[elastic-keldysh@pl1 ~]$ echo $PATH
/usr/share/Modules/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/opt/plesk/php/7.2/bin/
[elastic-keldysh@pl1 ~]$

We have successfully modified the PATH variable, but only for the existing session. If you want to persist the changes, then, you need to add the command in .bashrc/.profile/.bash_profile file depending on your shell type and OS. You can add to either of the file and test with the following command:

[elastic-keldysh@pl1 ~]$ echo "PATH=$PATH:/opt/plesk/php/7.2/bin/" >> .profile

Replace .profile with .bashrc or .bash_profile depending on the file that works for you. You may logout and relogin, and then run the echo command again to see if the $PATH is persisting or not.

How to Fix /usr/bin/env: ‘php’: Permission denied in Plesk

If you are seeing an error like the following in your Plesk:

bash-4.4$ laravel
/usr/bin/env: ‘php’: Permission denied

Your binary to php is probably being used through redirection like .bashrc file and an alias is hooked for your php command to work. A better way to do this, is to hook the php binary to your PATH variable. You may do this and fix the error by following this tutorial:

How to Add PHP in Default Path for Plesk / How to Fix -bash: php: command not found for Plesk User

Hope this helps. Thanks.

How to Add PHP in Default Path for Plesk / How to Fix -bash: php: command not found for Plesk User

If you have added SSH access to your plesk user using the following tutorial:

How to Enable SSH in Plesk User Domain

and then, tried to run php command like the following:

[elastic-keldysh@pl1 ~]$ php -v
-bash: php: command not found

You might have encountered the above error. This is because plesk do not store the php binary in your PATH variable locations. You may check your existing path variables here:

[elastic-keldysh@pl1 ~]$ echo $PATH
/usr/share/Modules/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin

Plesk stores it’s php binaries for different versions here:

/opt/plesk/php/

So, for example if you are trying to use PHP 7.4 binary, this would be like the following:

[elastic-keldysh@pl1 php]$ /opt/plesk/php/7.4/bin/php -v
PHP 7.4.10 (cli) (built: Sep  4 2020 03:49:35) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with the ionCube PHP Loader + ionCube24 v10.4.2, Copyright (c) 2002-2020, by ionCube Ltd.
    with Zend OPcache v7.4.10, Copyright (c), by Zend Technologies

So, to use only php -v, you need to add this bin path to your path variable. You may do that by running the following command:

PATH=$PATH:/opt/plesk/php/7.4/bin/

Now, you may run the following and it will work:

[elastic-keldysh@pl1 php]$ php -v
PHP 7.4.10 (cli) (built: Sep  4 2020 03:49:35) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with the ionCube PHP Loader + ionCube24 v10.4.2, Copyright (c) 2002-2020, by ionCube Ltd.
    with Zend OPcache v7.4.10, Copyright (c), by Zend Technologies

Now, we need to remember, this will only sustain for the existing session, if we log out and re login, this would be lost. To keep this permanent on each login, we need to put this in the .profile file. You may do this by running the following:

echo "PATH=$PATH:/opt/plesk/php/7.4/bin/" >> .profile

Once done, now you may try to login back again and see php -v is still working:

[elastic-keldysh@pl1 ~]$ exit
logout
[root@pl1 ~]# su - elastic-keldysh
Last login: Thu Oct  1 13:42:13 IST 2020 on pts/0
[elastic-keldysh@pl1 ~]$ php -v
PHP 7.4.10 (cli) (built: Sep  4 2020 03:49:35) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with the ionCube PHP Loader + ionCube24 v10.4.2, Copyright (c) 2002-2020, by ionCube Ltd.
    with Zend OPcache v7.4.10, Copyright (c), by Zend Technologies
[elastic-keldysh@pl1 ~]$

How to Enable SSH in Plesk User Domain

After you have created the domain from Plesk panel, go to Websites & Domains List, click on your domain to view details of your domain settings.

Now click on FTP access, and from the List click on the main username. In the FTP details for the user page, you will see an option says ‘Access to the server over SSH’ with a drop down that primarily says ‘Forbidden’. You may select the kind of SSH, you would like to give to your user. If you are familiar with the ‘jailshell’ in Cpanel, then it is the option that says ‘/bin/bash (chrooted)’, or you may select /bin/bash to give them normal shell.

Now, you may press ‘Apply’ to set SSH access to the user.

How to Copy a Disk Over SSH?

First, let’s see why do we need to copy a disk over SSH. One is of course for backup. For example if you have a VM on a LVM partition. You want to keep a copy of the block level backups, you prefer to create a snapshot of the lvm partition and then copy the disk as an image to your backup server. The other being quite the same, but for different purpose. What if you want to migrate a VM that you have created on an LVM partition, and then you want to migrate it as a raw file to another server? Or a LVM partition to another server? For those cases, the technique is pretty awesome.

Copy The Disk to a RAW Image

First, let’s learn how can copy a disk as raw image.

For example, you are sitting in your backup server. And you want to copy a disk or lvm partition or a partition of a disk, from a remote server to your backup server. And you want to keep the copy of the image, then you may run dd command as following from your backup server:

ssh [email protected] "dd if=/dev/vg0/v1092-kdkdksjuekksq" | dd of=/backup/v1092.raw

In our case, 10.10.10.10 is the IP of the server, that partition/disk currently reside. We are trying to copy a LVM partition namely: /dev/vg0/v1092-kdkdksjuekksq, just replace this one with the one your desired lvm partition. You may also do this for a disk like /dev/sda, the command would be like the following then:

ssh [email protected] "dd if=/dev/sda" | dd of=/backup/v1092.raw

Now as you have copied the disk/partition, you may look at what the partition holds by checking the data inside it. To know, how to mount a raw disk image, you may check the following:

How-to-Mount-raw-VM-disk-images-KVMorXenorVMW

Copy The Disk To Another Remote Disk over SSH

You may either copy the disk directly to a secondary disk you have on the backup/migrated server or dump the image that you copied to another disk/partition of same size or bigger. To copy directly a partition /dev/sda from another server, to a backup server with the secondary disk /dev/sdb, you may do the following:

ssh [email protected] "dd if=/dev/sda" | dd of=/dev/sdb

This would backup /dev/sda from 10.10.10.10 and restore to /dev/sdb drive you have on the server that ran the command.

To just dump the image file, that copied earlier on the other example to /dev/sdb, you may do the following:

dd if=/backup/v1092.raw of=/dev/sdb

Hope this helps.

How to Enable Query Logging in MySQL/MariaDB

For example, you manage a high traffic website, that utilizes an abstraction layer like an ORM to manage MySQL queries. Now, as a DevOps/System Admin, it becomes difficult for you to get a stat of which MySQL query being overused in the scenario. For these cases, one way, you may get some idea on what being overused, is called ‘MySQL General Logs’. Remember, it is very much different than the MySQL Slow Query Logging. It is not essential to have a slow query in the system to determine if your mysql is boggling. It is very much possible, there are queries, that take very small amount of time, but starves your CPU by executing many times and performs the same operation. Once you are able to identify them, you may utilize any Hashmap based caching strategy like Memcache or Redis or Simple file cache to reduce your load down on MySQL instance or cluster.

First, we create a query logging file and set the right permission:

touch /var/log/mysql_query.log
chown mysql:mysql /var/log/mysql_query.log

Once the file creation is done, now we can enable general log either by using mysql shell, if you would like to avoid restarting your mysql instance or in my.cnf file to keep the change permanent. A point to note, you should not do query logging all the time, as it decreases MySQL performance by 15-25%, which might hurt your overall production performance, plus the size of log will cumulatively increase if you have a server that performs over a thousand or more queries per second. 

# Type in your shell prompt
mysql

# this will open your mysql shell, you may run mysql commands as below:

mysql > SET global general_log = 1;
mysql > SET global log_output = '/var/log/mysql_query.log';

This should immediately advise mysql to push the logs to /var/log/mysql_query.log.

Now, if you observe the file, you may see the queries are coming up so quickly that you may hardly find anything out from it. The file has no output until you aggregate the result. If you have a large file, a better way to aggregate result by using Lotstash and Elasticsearch. We won’t do that here, that would be a topic for another blog post. We would instead use, some basic shell aggregation to see if we can determine anything useful from this. You may use the following tool, that list the last 10000 lines, then sort, and group the unique lines with the count and order by ascending to put the most frequent query at the end of the line:

tail -10000 /var/log/mysql_query.log | sort | uniq -c | sort -n

This will help you by giving the top most used query in last 10K queries. If the number is more than 5%, you need to pay attention to that. If it is the same query, that means, you may use a Hashmap based caching technique to reduce database boggling and improve performance.

Hope this helps.

How To Get Disk Serial Number in Megaraid

Question:

We can use smartctl to get the disk serial ID in case of disk replacement or crashes, with the following:

smartctl -a /dev/sdX

Where X is the device identifier like, for the first disk, this would be sda, second sdb etc. But in case the devices are behind the RAID, this command returns an error:

[root@tampa-lb ~]# smartctl -a /dev/sda
smartctl 7.0 2018-12-30 r4883 [x86_64-linux-3.10.0-1127.el7.x86_64] (local build)
Copyright (C) 2002-18, Bruce Allen, Christian Franke, www.smartmontools.org

Smartctl open device: /dev/sda failed: DELL or MegaRaid controller, please try adding '-d megaraid,N'

How to make this work?

Answer:

To get the serial numbers behind the LSI MegaRAID, you would first need to find out the device ID using LSI Megaraid tools. A quick way to install LSI Megaraid tool is available here:

How to: Install LSI Command Line Tool

One you have installed the LSI Megaraid command line tools, now you may use the following command to identify your device:

/opt/MegaRAID/MegaCli/MegaCli64 -PDList -aAll | egrep 'Slot\ Number|Device\ Id|Inquiry\ Data|Raw|Firmware\ state' | sed 's/Slot/\nSlot/g'

This would output something like the following:

Slot Number: 1
Device Id: 11
Raw Size: 447.130 GB [0x37e436b0 Sectors]
Firmware state: Online, Spun Up
Inquiry Data: 50026B72822A7D3A    KINGSTON SEDC500R480G                   SCEKJ2.3

In this server, it has one disk, but you may have multiple disk with different ‘Firemware state’ and ‘Device Id’. To use smartmontools, you need to pick the ‘Device Id’, mentioned here, which is 11. Now you can run the following command to get the device details using smartctl:

smartctl -d megaraid,N -a /dev/sdX

Here, N is the device ID, and X is the device name, you may get the device name using df -h command or fdisk -l. For our case, this command would be like the following:

smartctl -d megaraid,11 -a /dev/sda

This would print a lot of information about your device, but if you are looking to identify the Serial Number only, you may run the following:

~ smartctl -d megaraid,11 -a /dev/sda|grep Serial
Serial Number:    50026B72822A7D3A

One thing to note, we can also get Serial number from the MegaCli tools Inquiry data, you may have already noticed:

[root@tampa-lb ~]# /opt/MegaRAID/MegaCli/MegaCli64 -PDList -aAll | grep 'Inquiry Data'
Inquiry Data: 50026B72822A7D3A    KINGSTON SEDC500R480G                   SCEKJ2.3

Here, the first parameter in the return is the same as smartctl returns as Serial number, it’s because it’s the serial number that megacli gets/identifies as well.

How to Install Let’s Encrypt in Cpanel

Let’s Encrypt is a popular tool to use free SSL for your website. Cpanel comes with Sectigo free ssl service through requesting and pooling system. Although, you might feel interested in getting the SSL released immediately without a queue based approach, and would prefer to use Let’s Encrypt that’s why.

There are two ways, you may install Let’s Encrypt in Cpanel.

  1. Using Cpanel Plugin

First one would be using the plugin created by Cpanel. Login to your server as root:

ssh root@server_ip

Then, run the following to install Let’s Encrypt in your cpanel system

/usr/local/cpanel/scripts/install_lets_encrypt_autossl_provider

It might take a couple of minutes, then it should install Let’s Encrypt as a provider in AutoSSL.

Now, go to WHM >> Manage AutoSSL and select Let’s Encrypt as the provider instead of Sectigo Cpanel default. You need to check the Agreement rules under the Let’s Encrypt selection and you may create the account in Let’s Encrypt using the same tool.

Once done, your new SSLs would be issued using the Let’s Encrypt tool through Cpanel AutoSSL plugin.

2. Using FleetSSL

There is a 3rd party tool, existed before Cpanel provided a plugin for Let’s Encrypt. It’s FleetSSL. One key benefit of using FleetSSL is that, it allows the Cpanel end users to control issuing and renewing the SSL from Cpanel. One key cons of using FleetSSL is that, it is not free of charge, it comes with 30$ one time fees. But mainly hosting provider would not mind to use this as it is a nice addition for the end user feature set in a hosting provider’s point of view.

You may check for details here:

https://letsencrypt-for-cpanel.com/

Now, once you complete installing Let’s Encrypt SSL, you may now use Let’s Encrypt for different cpanel services like webmail/cpanel/whm/calenders/MTA services. You may check the following to know how to:

How To: Install AutoSSL for Server Hostname – Cpanel Server

How to Install Odoo 13 in CentOS 7

Odoo is currently one of the most popular tool for business purposes. It has a community edition, that allows managing ERP at very low cost. Odoo was previously known as OpenERP. Odoo requires to be installed on a dedicated server or VPS. Odoo 13 had come out on October, 2019. Odoo 14 hasn’t been released yet for production. I will have a straight forward how to on installing the latest Odoo 13 in CentOS 7.

Log in to your system and update

First step would be to login to your system and then update the system using yum.

ssh root@server_ip

You may check the CentOS version from the redhat release file using the following:

cat /etc/redhat-release

It should show you something like the following if you 

CentOS Linux release 7.8.2003 (Core)

Now, you may try updating the system with yum

yum update -y

Once done, now install the EPEL repository as we need it to satisfy a couple of dependecies:

yum install epel-release

Install Python 3.6 packages and Odoo dependencies

We need Python 3.6 at least to run Odoo 13. Odoo 12 had support for Python 3.5, unfortunately, Odoo 13 doesn’t. We will use ‘Software Collection (scl)’ repository to install and use Python 3.6. To find the available Python versions in SCL, you may check the following:

SCL Repository for Python

Now, to install Python 3.6 using SCL, we first need to install the SCL repository for Centos:

yum install centos-release-scl

Once the SCL is loaded, now, you may install the python 3.6 using the following command:

yum install rh-python36

Once the Python is installed, now we will install several tools and packages for Odoo dependencies with the following command:

yum install git gcc nano wget nodejs-less libxslt-devel bzip2-devel openldap-devel libjpeg-devel freetype-devel

Create Odoo User

We now need to create a system user and group for Odoo and define a home directory to /opt/odoo

useradd -m -U -r -d  /opt/odoo -s /bin/bash odoo

You may use any username here, but remember to create the same username for the PostgreSQL as well.

Install PostgreSQL

CentOS base repository unfortunately, comes with Postgresql 9.2. But we want to use PostgreSQL 9.6 for our Odoo installation. You may check the available PostgreSQL for CentOS 7 using the following command:

yum list postgresql*

As by default CentOS 7 does not provide the PostgreSQL 9.6, we would use PostgreSQL official repository to download and install the 9.6 version.

First, we install the Postgres Yum Repository using the following command:

yum install https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm

Now, you may install PostgreSQL 9.6 and related required packages using the following command:

yum install postgresql96 postgresql96-server postgresql96-contrib postgresql96-libs

Now, we need to initialize the postgres database and start it. You may do that using the following:

# Initialize the DB
/usr/pgsql-9.6/bin/postgresql96-setup initdb

# Start the database
systemctl start postgresql-9.6.service

Now you may enable Postgres to start when booting up using the systemctl enable command:

systemctl enable postgresql-9.6.service

Now, we need to create a database user for our Odoo installation. You may do that using the following:

su - postgres -c "createuser -s odoo"

Note: If you have created a different user for Odoo installation other than ‘odoo’ than you should change the username here as well.

Install Wkhtmltopdf

Wkhtmltopdf is a open source tool to make html in pdf format so that you may print pdf reports. This tool is used by Odoo and requires to be installed as dependency. CentOS 7 repository does not provide the latest version of this tool, and Odoo requires you to use the latest version. Hence, we require to download the latest version from the Wkhtmltopdf website and install it. To do that, you may first visit the page:

https://wkhtmltopdf.org/downloads.html

The page gives you the direct rpm download link for each version of CentOS/Ubuntu/Mac etc. Download the stable version for CentOS 7. At the time of writing, the URL for CentOS 7 x86_64 bit is the following:

https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox-0.12.6-1.centos7.x86_64.rpm

You may install this using the following:

cd /opt/
wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox-0.12.6-1.centos7.x86_64.rpm
yum localinstall wkhtmltox-0.12.6-1.centos7.x86_64.rpm

Install and Configure Odoo 13

If you have come all through here, that means you are done with the all dependency installations before starting to download Odoo 13 source code. We will download Odoo 13 from it’s Github repo and use virtualenv to create an isolated python environment to install this python software.

First, login as odoo from root:

su - odoo

Clone the Odoo source code from Github repository:

git clone https://www.github.com/odoo/odoo --depth 1 --branch 13.0 /opt/odoo/odoo13

This will bring the Odoo 13 branch from the Odoo repository and put it inside the folder /opt/odoo/odoo13

Now, we need to enable software collections in order to access python binaries:

scl enable rh-python36 bash

Then we need to create a virtual environment to complete the installation:

cd /opt/odoo
python3 -m venv odoo13-venv

Now, you may activate the virtual environment you have just created:

source odoo13-venv/bin/activate

Now, we upgrade the pip and install the wheel library:

pip install --upgrade pip
pip3 install wheel

Once done, now we can using pip3 to install all the required Python modules from the requirements.txt file:

pip3 install -r odoo13/requirements.txt

Once the installation is complete, now we can deactivate the virtual environment and get back to the root user

deactivate && exit ; exit

If you think, you will create custom modules, you may now create it and give odoo the permission accordingly:

mkdir /opt/odoo/odoo13-custom-addons
chown odoo: /opt/odoo/odoo13-custom-addons

Now, we can fill up the odoo configuration file. First open the odoo.conf file:

nano /etc/odoo.conf

You may paste the following inside:

[options]
; This is the password that allows database operations:
admin_passwd = set_the_password_to_create_odoo_database
db_host = False
db_port = False
db_user = odoo
db_password = False
addons_path = /opt/odoo/odoo13/addons,/opt/odoo/odoo13-custom-addons
; You can enable log file with uncommenting the next line
; logfile = /var/log/odoo13/odoo.log

Please do not forget to change the password ‘set_the_password_to_create_odoo_database’ with a new strong password. This would be used to create Odoo databases from the login screen.

Create the systemd service file and start Odoo 13

Now, we will create a service file, to be able to start, stop and restart Odoo daemon. To do that, first create a service file using the following:

nano /etc/systemd/system/odoo13.service

and paste the following:

[Unit]
Description=Odoo13
Requires=postgresql-9.6.service
After=network.target postgresql-9.6.service

[Service]
Type=simple
SyslogIdentifier=odoo13
PermissionsStartOnly=true
User=odoo
Group=odoo
ExecStart=/usr/bin/scl enable rh-python35 -- /opt/odoo/odoo13-venv/bin/python3 /opt/odoo/odoo13/odoo-bin -c /etc/odoo.conf
StandardOutput=journal+console

[Install]
WantedBy=multi-user.target

Now, save the file and exit.

Now, you need to reload the systemd daemon to be able to read the latest changes you have made to services. To do that, run:

systemctl daemon-reload

Finally, now we can start Odoo 13 instance using the following command:

systemctl start odoo13

If you are interested to check the status of the instance, you may do this:

systemctl status odoo13
[root@hr ~]# systemctl status odoo13
● odoo13.service - Odoo13
   Loaded: loaded (/etc/systemd/system/odoo13.service; enabled; vendor preset: disabled)
   Active: active (running) since Sun 2020-09-13 08:26:46 EDT; 23h ago
 Main PID: 24502 (scl)
   CGroup: /system.slice/odoo13.service
           ├─24502 /usr/bin/scl enable rh-python36 -- /opt/odoo/odoo13-venv/bin/python3 /opt/odoo/odoo13/odoo-bin -c /etc/odoo.conf
           ├─24503 /bin/bash /var/tmp/sclSWH04z
           └─24507 /opt/odoo/odoo13-venv/bin/python3 /opt/odoo/odoo13/odoo-bin -c /etc/odoo.conf

It show green active running, if everything worked out. If you see no error, you may now enable Odoo to start during the boot:

systemctl enable odoo13

If you would like to see the logs, you may either use the journal tools like the following:

journalctl -u odoo13

or uncomment the following line to log the debugs in /etc/odoo.conf

logfile = /var/log/odoo13/odoo.log

After making any change to /etc/odoo.conf, do not forget the restart the Odoo13 instance using systemctl.

Test the Installation

You may now test the installation using http://your_server_ip:8069. If everything worked, it should come up. If it doesn’t, you may try stopping your ‘firewalld’ to see if firewall is blocking the port or not:

systemctl stop firewalld

At Mellowhost, we provide Odoo installation and configuration assistance for absolute free of charge. If you are willing to try out any of our VPS for Odoo, you may do so and talk with us through the Live chat or the ticket for Odoo assistance.

Furthermore, Good luck.

How to Call a Controller Method from Tinker – Laravel

LARAVEL TINKER

If you love to debug and test things in an app shell like me, then you are also a big fan of Tinker in laravel. Tinker is the shell prompt for Laravel and can be used to test and run different commands in php inside the app. You may run the following to hop into the tinker shell in a laravel environment:

php artisan tinker

Once you hop in the tinker, you can call any model or run any php command from the shell.

HOW TO RUN CONTROLLER METHOD FROM TINKER

There are times, you might feel more interest into evaluating a large controller method. To run a controller method, we first need to enter the service container of laravel. Laravel providers a helper method called ‘app()’ to enter the service container. It can then use a method called ‘call’ to access and execute a method inside a controller namespace, like the following:

app()->call('App\Http\Controllers\AdminControllers@yourmethod');

Repace your controller name and the method name after @. One thing, you need to realize is that the method ‘call’ takes the method reference, not the function itself. That means, you can not add brackets () at the end of method name while giving it in the call method.

HOW TO PASS PARAMETERS TO CONTROLLER FROM TINKER

As discussed earlier, you are passing reference only, not the function, hence you can not pass parameters like we usually do in methods/functions. We need to pass this as an argument in array.

Here is a more constructive way to do this:

# let's make an instance of controller first, can be done using make method of service container
$controller = app()->make('App\Http\Controllers\AdminControllers');

# now let's call the method, inside the container, method name is 'getNewsByCatId'
app()->call([$controller, 'getNewsByCatId']);

# pass a parameter called id = 5
app()->call([$controller, 'getNewsByCatId'], ['id' => 5]);