How to create a file of specific size using Linux command line

Run for a second:

yes "some text" > testfile.txt

Reduce size:

truncate -s 50M testfile.txt

Create 50M file using fallocate command

fallocate -l 52428800 testfile.txt

To be more exact using inline arithmetic:

fallocate -l $((50*1024*1024)) > testfile.txt
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How to generate Self-Signed SSL on cPanel server using command line

Run and put your domain:

read -p "Domain: " domain; username=`/scripts/whoowns $domain`; email=`grep @ /var/cpanel/users/$username |tail -n1 |cut -d '=' -f2|sed -e 's/@/\%40/'`; whmapi1 generatessl domains=$domain countryName=US stateOrProvinceName=Texas localityName=Houston organizationName="The Justice League of GG" emailAddress=$email pass=`openssl rand -base64 15` keysize=2048 skip_certificate=0

Now use WHM to install it

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How to disable swap partition

To see your swap usage run the following:

free -m

To disable swap without reboot and just temporary run the following:

sudo swapoff -a

This will wipe out used swap space and disable it

To get this enabled again run next:

sudo swapon -a

To disable swap permanently you need to edit /etc/fstab as root and comment out a line related to swap

For example:

cat /etc/fstab |grep swap

# swap was on /dev/nvme0n1p6 during installation
#UUID=d10c1d70-bb88-43fc-bbe2-e17592b660ba none swap sw 0 0

Then reboot your machine to apply the change or try to run next:

mount -a

To reboot run:


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How to calculate innodb_buffer_pool_size value

Run to the following command to start calculation:

(SELECT SUM(data_length+index_length) Total_InnoDB_Bytes
FROM information_schema.tables WHERE engine='InnoDB') A;


Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 60295069
Server version: 10.3.34-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

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How to update reseller’s subaccounts disk quota and bandwidth on cPanel server

Useful if you have plan limited by:

– limitation by amount of cPanel accounts
– bandwidth limitation
– disk space limitation
– overselling disabled

Update reseller’s packages with new limits via command line

sed -i -e "s/QUOTA=.*/QUOTA=2000/g" /var/cpanel/packages/resellerusername_*
sed -i -e "s/BWLIMIT=.*/BWLIMIT=20000/g"
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How to specify which IP address to use for curl or wget commands

Useful when you try to send a request from cPanel shell from your Dedicated IP address

For curl you need to use –interface to specify IP address


curl --interface

For wget you need to use –bind-address to set IP from which you need to send a request

wget --bind-address=
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