Mysql enable error logging

Was attempting to get the mysql error_log to work. The issue was that skip_log_error was being passed as mysqld param.

Using mariadb

# Is error_log set
$ cat /etc/mysql/mariadb.conf.d/50-server.cnf | grep log_error

log_error = /var/log/mysql/error.log

# Is skip_log_error removed or commented out
$ cat /etc/mysql/mariadb.conf.d/50-mysqld_safe.cnf | grep skip_log_error


# You may already have mysqld running with skip-log-error param which will prevent error_log from working
$ ps aux | grep skip-log-error

mysql    29703  0.0  1.4 662768 168708 ?       Sl   May01   0:36 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --skip-log-error --pid-file=/var/run/mysqld/ --socket=/var/run/mysqld/mysqld.sock --port=3306

# stop mysqld by killing process
$ kill 29703

# restart mysql
$ sudo /etc/init.d/mysql restart

# view log variables to determine if working
$ mysql -uUsername -pPassword -se "SHOW VARIABLES" | grep -e log_error -e general_log -e slow_query_log
mysql some log variables

Mysql Error: too many open files

# error: ERROR 1018 (HY000): Can’t read dir of ‘.’ (errno: 24)

# Super user
$ sudo su

# See what mysql files are open
$ lsof -u mysql

# Count how many mysql files are open
$ lsof -u mysql | wc -l

# close mysql files
$ kill -9 `lsof -t -u mysql`

# sources

SNMP Getting Started

# install
sudo apt-get install snmp snmpd snmp-mibs-downloader

# configuration
# server
$ sudo nano /etc/snmp/snmpd.conf

rocommunity VegetaRocks
syslocation Vegeta planet 
sysContact Vegeta <>;

# restart snmpd
$ sudo /etc/init.d/snmpd restart

# Test. On client
$ snmpwalk -v1 -c VegetaRocks
$ snmpget -v1 -c VegetaRocks

# example of traffic in wireshark
snmp traffic wireshar

# list of SNMP OID

# sources

Zabbix installation and setup

Ubuntu 16.04 LTS (xenial):

$ wget
$ dpkg -i zabbix-release_3.0-1+xenial_all.deb
$ apt-get update
$ sudo apt-get install zabbix-agent zabbix-server-mysql zabbix-frontend-php snmpd php5.6-mysql php5.6-curl
$ sudo nano /etc/php/5.6/apache2/php.ini

; Defines the default timezone used by the date functions
date.timezone = America/Sao_Paulo

$ sudo /etc/init.d/apache2 restart

php info date

Determine what port zabbix listening to. Should be either or all 10050 and 10051. One for agent another for server.
$ sudo netstat -tlnp | grep zabbix
zabbix port listening


Default Username: Admin
Default Password: zabbix

Error Solution: The frontend does not match Zabbix database
zabbix database installation error

You should first populate the database with the sql file provided in /usr/share/doc/zabbix-server-mysql/create.sql

Depending on the size allowed in phpmyadmin its best to import thru the command line. Also this allows to edit the file if any errors (possible 1709)
$ mysql -u root -p zabbix < create.sql

Configure port
If you have the incorrect port set you will get this error
Zabbix server is running
To view the zabbix port (you may need to start zabbix)
$ sudo /etc/init.d/zabbix-agent restart
$ sudo netstat -tlnp | grep zabbix
To change web port
$ sudo nano /etc/zabbix/web/zabbix.conf.php

$ZBX_SERVER      = '';
$ZBX_SERVER_PORT = '10050';

To change agent port
$ sudo nano /etc/zabbix/zabbix_agentd.conf

### Option: ListenPort
#	Agent will listen on this port for connections from the server.
# Mandatory: no
# Range: 1024-32767
# Default:

If you want reinstall zabbix. To get the installation screen
delete /etc/zabbix/web/zabbix.conf.php
go to http://localhost/zabbix/setup.php

# comment out the line 'mibs'
$ sudo nano /etc/snmp/snmp.conf

# As the snmp packages come without MIB files due to license reasons, loading
# of MIBs is disabled by default. If you added the MIBs you can reenable
# loading them by commenting out the following line.
#mibs :

# error log location

possible errors

server error:
[Z3001] connection to database 'zabbix' failed: [1045] Access denied for user 'zabbix'@'localhost' (using password: NO)
mysql>grant all privileges on zabbix.* to zabbix@localhost identified by 'abc123'
$ sudo nano file:/etc/zabbix/zabbix_server.conf

### Option: DBPassword
#	Database password. Ignored for SQLite.
#	Comment this line if no password is used.
# Mandatory: no
# Default:

agent error:
$ tail -f zabbix_agentd.log
failed to accept an incoming connection: connection from "" rejected, allowed hosts: ""
zabbix_agentd.conf 'Server=...' need to match /etc/zabbix/web/zabbix.conf.php '$ZBX_SERVER'
$ sudo nano /etc/zabbix/zabbix_agentd.conf


$ sudo /etc/init.d/zabbix-agent restart


Virtual box Increase disk size

command example
$ VBoxManage modifyhd /home/user/VirtualBox\ VMs/windows7/windows7.vdi --resize 50000

I had an issue where new memory was not showing up in GParted GUI to be allocated. I cloned the virtual drive and use that one instead and it worked

C sharp (C#) Hello world

create a cs file hello-world.cs and add code.

run the file in cmd
C:\Desktop> C:\Windows\Microsoft.NET\Framework64\v3.5\csc.exe hello_word.cs

then a executable will be created called hello_word.exe. That is your program. Run that to run you program.