Category: Linux

Install MySQL 8 on Ubuntu/Debian
To install MySQL 8 on Ubuntu/Debian, download the .deb repository file from

https://dev.mysql.com/downloads/repo/apt/

Following link may change, so always get newer version download link from above url.
```
wget https://dev.mysql.com/get/mysql-apt-config_0.8.24-1_all.deb
dpkg -i mysql-apt-config_0.8.24-1_all.deb
```
It ask you to select MySQL version, default is 8, just press down arrow and select “Ok”.

Now you are ready to install MySQL 8, you need to run apt update before you can install.
```
apt update
apt install mysql-server
```
It ask you to enter password.

Next it ask you to select password format.

MySQL 8 have a different authentication plugin, that use more secure password format. You can select Legacy Authentication for compatibility with MySQL version 5.x

Changing MySQL version

if you want to install differnt MySQL version, uninstall current MySQL version, then select a differnt MySQL version by running
```
dpkg-reconfigure  mysql-apt-config
```
MySQL 8 apt Error The following signatures were invalid
mysql
April 22, 2018
error: no acceptable C compiler found
When compiling software from source i get error
```
configure: error: no acceptable C compiler found in $PATH
```
To fix error, on CentOS, run
```
yum install gcc -y
```
On Debian/Ubuntu
```
apt install build-essential
```
Errors
April 22, 2018
Dig
dig is a command line tool like nslookup used to check dns

Find Reverse-DNS/PTR using dig, nslookup, host
Requesting a zone trasnfer with dig

Here is the basic usage
```
dig DOMAIN_NAME
```
dig have multiple sections, ANSWER SECTION is what you need to look for. After answer section, it shows some info about DNS server used to query.

+short

+short option allow you to just slow the answer.
```
root@ok-vm:~# dig +short serverok.in
104.28.18.89
104.28.19.89
root@ok-vm:~# 
```
To find Specific Record type
```
dig DOMAIN_NAME RECORD_TYPE
```
Example
```
root@ok-vm:~# dig +short serverok.in mx
5 alt1.aspmx.l.google.com.
5 alt2.aspmx.l.google.com.
10 alt3.aspmx.l.google.com.
11 alt4.aspmx.l.google.com.
1 aspmx.l.google.com.
root@ok-vm:~# 
```
Dig show detailed info

You can use +trace to get more detailed info on dig query.
```
dig +trace RECORD_TYPE DOMAIN_NAME
```
Example
```
dig +trace ns boby.serverok.in
```
See nslookup, dns
April 21, 2018
phpstrom

Installing PhpStorm on Ubuntu

April 16, 2018
Installing PhpStorm on Ubuntu
Download latest version of PhpStorm from

https://www.jetbrains.com/phpstorm/download/#section=linux

You get a file with name like “PhpStorm-2018.1.1.tar.gz”

Extract the file, put in a folder, i normally put it in directory ~/programs/phpstrom/

Now open terminal, go to folder
```
cd ~/programs/phpstrom/bin
```
Run phpStrom with command
```
./phpstorm.sh
```
Create Application Shortcut

Creating application shortcut is easy. Just go to Tools > Create Desktop Entry.

phpstrom
April 16, 2018
Clean Magento session folder
On a VPS hosting Magento 1.9 disk was getting full. On checking, found var/session folder taking too much disk space.

Disk usage was 34 GB.

This folder is used to store PHP session files. You can delete them.

I created a cronjob to delete the session files that are older.
```
mkdir /usr/serverok/
vi /usr/serverok/clean-session
```
Add following content
```
#!/bin/bash

/bin/find /path/to/var/session -type f -mtime +10 -name "sess_*" -delete
```
Make it executable
```
chmod 755 /usr/serverok/clean-session
```
Set a cronjob to run everyday
```
@daily /usr/serverok/clean-session > /dev/null 2>&1
```
Method 2 – Strong session in database

Edit file
```
vi app/etc/local.xml
```
Find
Replace with
Magento
April 15, 2018

Install Monit on Ubuntu

Monit can be used to monitor services, restart them if required. To install monit, run

apt -y install monit

To start monit, run

systemctl start monit

Monitor Apache

vi /etc/monit/conf-available/apache2-custom

Add

check process apache with pidfile /var/run/apache2/apache2.pid
    group www-data
    start program = "/etc/init.d/apache2 start"
    stop program  = "/etc/init.d/apache2 stop"
    if failed host localhost port 80 protocol http then restart
    if 5 restarts within 5 cycles then timeout

Activate the rule with

ln -s /etc/monit/conf-available/apache2-custom /etc/monit/conf-enabled/apache2-custom

Restart monit with

systemctl restart monit

Testing If Monit works

Open 2 terminals. On one, tail the monit logs with

tail -f /var/log/monit.log

On other terminal, stop Apache

service apache2 stop

Within 2 minutes, monit will restart apache web server.

monit

April 14, 2018

Unban an IP from CSF Firewall
To unban an IP from CSF firewall, run
```
csf -dr IP_ADDR
```
Here i have an IP blocked in firewall.
```
[root@server22 ~]# iptables -L -n | grep 13.224.29.193
DROP       all  --  13.224.29.193        0.0.0.0/0           
LOGDROPOUT  all  --  0.0.0.0/0            13.224.29.193       
[root@server22 ~]# 
```
To see if CSF is blocking the IP, run
```
csf -g IP_ADDR
```
Example

This command also give reason for why the IP is blocked.

Lets unban the IP address with command
```
csf -dr IP_ADDR
```
Now IP should not be listed in iptables, verify it with
```
iptables -L -n | grep IP_ADDR
```
csf
April 13, 2018
Virtualmin Downloading PHP file
After setting up new site in virtualmin, PHP file get downloaded instead of getting executed.

To fix the problem, edit file
```
vi /etc/httpd/conf.d/php.conf
```
Find
```
    SetHandler application/x-httpd-php
```
Replace with
```
AddHandler php7-script .php
```
Restart apache
```
service httpd restart
```
virtualmin
April 12, 2018

Install ionCube on Debian 9

Download latest version of ionCube loader from

cd /usr/local/src
wget https://downloads.ioncube.com/loader_downloads/ioncube_loaders_lin_x86-64.tar.gz
tar xvf ioncube_loaders_lin_x86-64.tar.gz
cd ioncube/

Check PHP version with

php -v

On Debian 9, default will be PHP 7.0, so you need to use file ioncube_loader_lin_7.0.so

Find PHP extension_dir, this is where you need to put PHP extensions.

root@ip-172-31-44-173:/usr/local/src/ioncube# php -i | grep  extension_dir
extension_dir => /usr/lib/php/20151012 => /usr/lib/php/20151012
root@ip-172-31-44-173:/usr/local/src/ioncube#

Copy the file to extension directory

cp /usr/local/src/ioncube/ioncube_loader_lin_7.0.so /usr/lib/php/20151012

Enable ionCube loader with

echo "zend_extension=ioncube_loader_lin_7.0.so" > /etc/php/7.0/mods-available/ioncube.ini
ln -s /etc/php/7.0/mods-available/ioncube.ini /etc/php/7.0/cli/conf.d/01-ioncube.ini
ln -s /etc/php/7.0/mods-available/ioncube.ini /etc/php/7.0/apache2/conf.d/01-ioncube.ini

Now php -m will show ioncube

root@ip-172-31-44-173:~# php -m | grep ion
ionCube Loader
Reflection
session
the ionCube PHP Loader (enabled) + Intrusion Protection from ioncube24.com (unconfigured)
root@ip-172-31-44-173:~#

Restart apache

service apache2 restart

ioncube | ionCube on Debian 8

April 11, 2018

Unable to Write to Disk – Inodes Full
On a server, can’t write to disk. I checked disk usage with
```
df -h
```
Everything is good. Next i checked Inodes usage with
```
df -hi
```
Inodes usage was 100%

[root@w8bd-blkx ~]# df -hi
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/ploop36812p1 6.1M 6.1M 5 100% /
/dev/simfs 6.1M 6.1M 5 100% /tmp
/dev/simfs 6.1M 6.1M 5 100% /var/tmp
none 1.0M 160 1.0M 1% /dev
[root@w8bd-blkx ~]#

This normally happen when you have too many smaller files.

First of all free up some Inodes by removing unwanted log files, most of the time you can delete some logs in /var/log folder.

To find where the Inodes are used up, run command
```
find / -xdev -printf '%h\n' | sort | uniq -c | sort -k 1 -n
```
The command will display Inodes usage for folder sorted by Inodes.

In this case, httpdocs/var/session had too many session files. I removed all session files, that fixed the problem. To avoid this happening again, i created a cronjob, that delete old session files every day.

hdd
April 11, 2018
Sync Files between 2 servers
Here are some tools that can be used to sync files between 2 servers.
- rsync
- lsyncd
- unison
April 9, 2018

Category: Linux

Dig show detailed info