Recently I ran a command in mysql that resulted in this error:

mysql: [ERROR] unknown variable 'sql_mode=IGNORE_SPACE,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'

So I had to add a line to the mysql config file. In Ubuntu 16:

# nano /etc/mysql/mysql.conf.d/mysqld.cnf

Add the following line under mysqld


[mysqld]
sql_mode = "STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

Restart mysql:

# systemctl restart mysql

UFW is installed by default on Ubuntu. If it has been uninstalled for some reason, yYou can install it with apt-get:

# sudo apt-get install ufw

Check the Status

# sudo ufw status verbose

By default, UFW is disabled so you should see something like this:

Output:


# Status: inactive

If UFW is active, the output will say that it’s active, and it will list any rules that are set. For example, if the firewall is set to allow SSH (port 22) connections from anywhere, the output might look something like this:

Output:


Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
22/tcp                     ALLOW IN    Anywhere

Let’s set your UFW rules back to the defaults so we can be sure that you’ll be able to follow along with this tutorial. To set the defaults used by UFW, use these commands:


# sudo ufw default deny incoming
# sudo ufw default allow outgoing

As you might have guessed, these commands set the defaults to deny incoming and allow outgoing connections. These firewall defaults, by themselves, might suffice for a personal computer but servers typically need to respond to incoming requests from outside users. We’ll look into that next.

Allow SSH Connections

To configure your server to allow incoming SSH connections, you can use this UFW command:

# sudo ufw allow ssh

this command works the same as the one above:

# sudo ufw allow 22
# sudo ufw allow 2222

Now that your firewall is configured to allow incoming SSH connections, we can enable it

# sudo ufw enable

HTTP—port 80
HTTP connections, which is what unencrypted web servers use, can be allowed with this command:

# sudo ufw allow http

If you’d rather use the port number, 80, use this command:


# sudo ufw allow 80

HTTPS—port 443
HTTPS connections, which is what encrypted web servers use, can be allowed with this command:

pre>
# sudo ufw allow https

If you’d rather use the port number, 443, use this command:

# sudo ufw allow 443

FTP—port 21
FTP connections, which is used for unencrypted file transfers (which you probably shouldn’t use anyway), can be allowed with this command:

# sudo ufw allow ftp

If you’d rather use the port number, 21, use this command:

# sudo ufw allow 21/tcp

Allow Specific Port Ranges
You can specify port ranges with UFW. Some applications use multiple ports, instead of a single port.

For example, to allow X11 connections, which use ports 6000-6007, use these commands:


# sudo ufw allow 6000:6007/tcp
# sudo ufw allow 6000:6007/udp

When specifying port ranges with UFW, you must specify the protocol (tcp or udp) that the rules should apply to. We haven’t mentioned this before because not specifying the protocol simply allows both protocols, which is OK in most cases.

Allow Specific IP Addresses
When working with UFW, you can also specify IP addresses. For example, if you want to allow connections from a specific IP address, such as a work or home IP address of 15.15.15.51, you need to specify “from” then the IP address:


# sudo ufw allow from 15.15.15.51

You can also specify a specific port that the IP address is allowed to connect to by adding “to any port” followed by the port number. For example, If you want to allow 15.15.15.51 to connect to port 22 (SSH), use this command:


# sudo ufw allow from 15.15.15.51 to any port 22

Allow Subnets
If you want to allow a subnet of IP addresses, you can do so using CIDR notation to specify a netmask. For example, if you want to allow all of the IP addresses ranging from 15.15.15.1 to 15.15.15.254 you could use this command:

# sudo ufw allow from 15.15.15.0/24

Likewise, you may also specify the destination port that the subnet 15.15.15.0/24 is allowed to connect to. Again, we’ll use port 22 (SSH) as an example:


# sudo ufw allow from 15.15.15.0/24 to any port 22

Allow Connections to a Specific Network Interface
If you want to create a firewall rule that only applies to a specific network interface, you can do so by specifying “allow in on” followed by the name of the network interface.

You may want to look up your network interfaces before continuing. To do so, use this command:


ip addr
Output Excerpt:
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state
...
3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default 
...

The highlighted output indicates the network interface names. They are typically named something like “eth0” or “eth1”. So, if your server has a public network interface called eth0, you could allow HTTP traffic (port 80) to it with this command:


# sudo ufw allow in on eth0 to any port 80

Doing so would allow your server to receive HTTP requests from the public Internet.

Or, if you want your MySQL database server (port 3306) to listen for connections on the private network interface eth1, for example, you could use this command:


# sudo ufw allow in on eth1 to any port 3306

This would allow other servers on your private network to connect to your MySQL database.

Deny Connections
If you haven’t changed the default policy for incoming connections, UFW is configured to deny all incoming connections. Generally, this simplifies the process of creating a secure firewall policy by requiring you to create rules that explicitly allow specific ports and IP addresses through.

To write deny rules, you can use the commands that we described above except you need to replace “allow” with “deny”.

For example to deny HTTP connections, you could use this command:


# sudo ufw deny http

Or if you want to deny all connections from 15.15.15.51 you could use this command:


# sudo ufw deny from 15.15.15.51

If you need help writing any other deny rules, just look at the previous allow rules and update them accordingly.

Now let’s take a look at how to delete rules.

Delete Rules
Knowing how to delete firewall rules is just as important as knowing how to create them. There are two different ways specify which rules to delete: by rule number or by the actual rule (similar to how the rules were specified when they were created). We’ll start with the delete by rule number method because it is easier, compared to writing the actual rules to delete, if you’re new to UFW.

By Rule Number
If you’re using the rule number to delete firewall rules, the first thing you’ll want to do is get a list of your firewall rules. The UFW status command has an option to display numbers next to each rule, as demonstrated here:


# sudo ufw status numbered
Numbered Output:
Status: active

     To                         Action      From
     --                         ------      ----
[ 1] 22                         ALLOW IN    15.15.15.0/24
[ 2] 80                         ALLOW IN    Anywhere

If we decide that we want to delete rule 2, the one that allows port 80 (HTTP) connections, we can specify it in a UFW delete command like this:


# sudo ufw delete 2

This would show a confirmation prompt then delete rule 2, which allows HTTP connections. Note that if you have IPv6 enabled, you would want to delete the corresponding IPv6 rule as well.

By Actual Rule
The alternative to rule numbers is to specify the actual rule to delete. For example, if you want to remove the “allow http” rule, you could write it like this:


# sudo ufw delete allow http

You could also specify the rule by “allow 80”, instead of by service name:


# sudo ufw delete allow 80

This method will delete both IPv4 and IPv6 rules, if they exist.

How To Disable UFW (optional)
If you decide you don’t want to use UFW for whatever reason, you can disable it with this command:


# sudo ufw disable

Any rules that you created with UFW will no longer be active. You can always run sudo ufw enable if you need to activate it later.

Reset UFW Rules (optional)
If you already have UFW rules configured but you decide that you want to start over, you can use the reset command:


# sudo ufw reset

This will disable UFW and delete any rules that were previously defined. Keep in mind that the default policies won’t change to their original settings, if you modified them at any point. This should give you a fresh start with UFW.

How can I increase the space on an Ubuntu Boot Partition?

When trying to install programs on my Ubuntu server but the server is not allowing me to do that because the boot partition ‘/dev/sda1’ is full.

/dev/sda1       236M   236M  0M  100% /boot

By default Ubuntu has a small /boot partition. When you have auto updates enabled this can cause some issues as newer kernels are not automatically purged. So, you will need to increase the size of the Ubuntu Boot Partition.

You can add the following to your crontab to run every Sunday night at 11:30PM to clean out old kernels. You can do so by running crontab -e as root and adding the following line at the bottom of that file.


30 23 * * 6 apt-get autoremove

You will also want to reboot every so often so newer kernels are being used and newer kernels are not causing the issues. I would suggest rebooting at your earliest convenience and running


# apt-get autoremove 

to load the newest kernel and delete the older kernels already installed on your server.

However, once rebooted and the autoremove command is done more disk space will be free.

Info

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            990M  4.0K  990M   1% /dev
tmpfs           201M  716K  200M   1% /run
/dev/dm-0        15G  1.9G   12G  14% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
none            5.0M     0  5.0M   0% /run/lock
none           1001M     0 1001M   0% /run/shm
none            100M     0  100M   0% /run/user
/dev/sda1       236M   72M  152M  32% /boot

$ du -shcx /boot/*
1.2M /boot/abi-3.16.0-30-generic
1.2M /boot/abi-3.16.0-77-generic
169K /boot/config-3.16.0-30-generic
169K /boot/config-3.16.0-77-generic
6.7M /boot/grub
21M /boot/initrd.img-3.16.0-30-generic
21M /boot/initrd.img-3.16.0-77-generic
du: cannot read directory ‘/boot/lost+found’: Permission denied
12K /boot/lost+found
174K /boot/memtest86+.bin
175K /boot/memtest86+.elf
176K /boot/memtest86+_multiboot.bin
3.4M /boot/System.map-3.16.0-30-generic
3.4M /boot/System.map-3.16.0-77-generic
6.1M /boot/vmlinuz-3.16.0-30-generic
6.2M /boot/vmlinuz-3.16.0-77-generic
70M total

  
				 			
			

How to install PHP 5.6 on Ubuntu 16.04 Xenial and replace php 7. Let’s assume you have a fresh Ubuntu 16.04 server.

Install add-apt-repository:


# sudo apt-get install python-software-properties

Add repository for PHP 5.6:


# sudo add-apt-repository -y ppa:ondrej/php

Update package lists:


sudo apt-get update


Install php5-fpm:


# sudo apt-get install php5.6-fpm

Check the result:


# php -v
PHP 7.0.4-7ubuntu2.1 (cli) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies


Run the following:

# sudo mv /usr/bin/php /usr/bin/php7
# sudo mv /usr/bin/php5.6 /usr/bin/php

Check again


# php -v
PHP 5.6.23-2+deb.sury.org~xenial+1 (cli) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies

Restart Apache

# service apache2 restart

How to install Apache, MySQL and PHP on Ubuntu 14.04

Update

# sudo apt-get update

Apache

# sudo apt-get install apache2

Install MySQL

# sudo apt-get install mysql-server php5-mysql
# sudo mysql_install_db
# mysql_secure_installation

Install PHP

# sudo apt-get install php5 libapache2-mod-php5 php5-mcrypt

Restart Server

# sudo /etc/init.d/apache2 restart

Check Apache

Open a web browser and navigate to http://IPADDRESS. You should see a message saying It works!

Check PHP

# php -r 'echo "\n\nYour PHP installation is working fine.\n\n\n";'

Getting error for Plesk auto installer on Ubuntu 12 Trusty:


Reading package lists...
W: GPG error: http://autoinstall.plesk.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 227C38D6AF741DEB
W: GPG error: http://autoinstall.plesk.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 227C38D6AF741DEB
W: GPG error: http://autoinstall.plesk.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 227C38D6AF741DEB
W: GPG error: http://autoinstall.plesk.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 227C38D6AF741DEB
W: GPG error: http://autoinstall.plesk.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 227C38D6AF741DEB
Gathering information about installed license key...
Checking whether the package dependencies are resolved.
E: Unable to correct problems, you have held broken packages.
---X--- `apt-get` output ---------------------
Reading package lists...
Building dependency tree...
Reading state information...
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
plesk-base : Depends: sw-engine (>= 2.13.9) but it is not going to be installed
plesk-core : Depends: libmyodbc but it is not installable
Depends: pigz but it is not installable
plesk-php56-dba : Depends: libdb5.1 but it is not installable
plesk-php56-imap : Depends: libc-client2007e but it is not installable
plesk-php56-mcrypt : Depends: libmcrypt4 but it is not installable
plesk-service-node-utilities : Depends: libxml-dumper-perl but it is not installable
Depends: sysv-rc-conf but it is not installable
pp12.0.18-bootstrapper : Depends: sw-engine (>= 2.0) but it is not going to be installed
psa-courier-imap : Depends: libdb5.1 but it is not installable
Depends: libssl0.9.8 but it is not installable
psa-php5-configurator : Depends: php5-imap but it is not installable
psa-updates : Depends: sw-engine (>= 2.13.12) but it is not going to be installed

Check following:

1. /etc/apt/sources.list

2. uncomment the deb repos listed as universal/multiverse

3. re-run apt-get update

4. re-run plesk installer

I have also noticed that it tends to give an error about the hostname as well, which I resolved by temporarily setting the hostname to pretty much anything, such as newserver.

Other Information: http://forum.odin.com/threads/plesk-autoinstaller-gpg-error.332686/

Check your current timezone by just running


# date
Thu Mar 21 18:02:49 MST 2012

Or checking the timezone file at


# more /etc/timezone
US/Arizona

So to change it just run


$ sudo dpkg-reconfigure tzdata

And follow on screen instructions. Easy.

Also be sure to restart cron as it won’t pick up the timezone change and will still be running on UTC.

# /etc/init.d/cron stop
# /etc/init.d/cron start

sysv-rc-conf is an alternate option for Ubuntu.


# sudo apt-get install sysv-rc-conf


# sysv-rc-conf --list xxxx

Also, to disable a process at boot, you could simply disable it by:

# sudo update-rc.d apache2 disable

and then if you would like to enable it again:


# sudo update-rc.d apache2 enable