How to expand a disk in Azure
Windows
https://querysurge.zendesk.com/hc/en-us/articles/115002530951-Azure-Expand-Disk-
Linux
https://docs.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks
Linux, Windows, Software Tips, Articles and Hacks
How to expand a disk in Azure
Windows
https://querysurge.zendesk.com/hc/en-us/articles/115002530951-Azure-Expand-Disk-
Linux
https://docs.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks
Subnet to Mask Bits conversion table
Mask CIDR Length (Mask Bits)
128.0.0.0 1
192.0.0.0 2
224.0.0.0 3
240.0.0.0 4
248.0.0.0 5
252.0.0.0 6
254.0.0.0 7
255.0.0.0 8
255.128.0.0 9
255.192.0.0 10
255.224.0.0 11
255.240.0.0 12
255.248.0.0 13
255.252.0.0 14
255.254.0.0 15
255.255.0.0 16
255.255.128.0 17
255.255.192.0 18
255.255.224.0 19
255.255.240.0 20
255.255.248.0 21
255.255.252.0 22
255.255.254.0 23
255.255.255.0 24
255.255.255.128 25
255.255.255.192 26
255.255.255.224 27
255.255.255.240 28
255.255.255.248 29
255.255.255.252 30
255.255.255.254 31
255.255.255.255 32
How to test apache.
Create 2 files:
testload.php
test.php
Create a php file testload.php that checks the existence of another file named test.php in the same directory of two CentOS 7 servers with the same hardware characteristics and load but with different MPM. One of them will use event and the other one will use prefork.
<!--?php $filename = 'test.php'; if (file_exists($filename)) { echo "The file $filename exists"; } else { echo "The file $filename does not exist"; } ?-->
With ab, we will sent 50 (-c 50) concurrent requests at the same time and repeat the test 1000000 times
# ab -c 50 -n 100000 http://localhost/testload.php
200 simultaneous requests until 2000 requests are completed:
# ab -k -c 100 -n 2000 localhost/testload.php
Another test to localhost
PREFORK
]# ab -c 50 -n 100000 http://localhost/index.html This is ApacheBench, Version 2.3 <$Revision: 1430300 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking localhost (be patient) Completed 10000 requests Completed 20000 requests Completed 30000 requests ^C Server Software: Apache/2.4.6 Server Hostname: localhost Server Port: 80 Document Path: /index.html Document Length: 15167 bytes Concurrency Level: 50 Time taken for tests: 3596.808 seconds Complete requests: 34570 Failed requests: 0 Write errors: 0 Non-2xx responses: 34571 Total transferred: 537122767 bytes HTML transferred: 524331497 bytes Requests per second: 9.61 [#/sec] (mean) Time per request: 5202.210 [ms] (mean) Time per request: 104.044 [ms] (mean, across all concurrent requests) Transfer rate: 145.83 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 0 0.1 0 3 Processing: 213 5198 241.5 5203 10154 Waiting: 174 4428 227.6 4435 9302 Total: 214 5198 241.5 5203 10154 Percentage of the requests served within a certain time (ms) 50% 5203 66% 5264 75% 5302 80% 5327 90% 5391 95% 5449 98% 5532 99% 5617 100% 10154 (longest request)
The term hairpinning comes from the fact that the traffic comes from one source into a router or similar devices, makes a U-turn and goes back the same way it came.
Visualize this and you see something that looks like a hairpin.
Hairpin NAT is a useful technique for accessing an internal server using a public IP. Since you are using a public IP to attempt to access a server in your network, the traffic will attempt to go out to the internet. In order to reach the server, the traffic will need to be redirected to the correct location.
The issue with this article is that you need to load a website or use curl to access the website on an internal IP that is set up as NAT to a public IP.
Scenario:
Server1 – Web Server. Has a public IP 214.44.55.44 and is behind a firewall with the private IP 10.0.0.12.
When you try and load the site on this server, it does not load.
Fix: Set up hosts file to point to the private IP.
Use this information when changing the hostname in centos 7.
Ways to show the hostname
# hostname # hostname -s # hostname -f # cat /etc/hostname # hostnamectl
How to change the hostname.
In order to change or set a CentOS 7 machine hostname, use the hostnamectl command as shown in the below command excerpt.
# hostnamectl set-hostname your-new-hostname
In order to apply the new hostname, a system reboot is required, issue one of the below commands in order to reboot a CentOS 7 machine.
# init 6 # systemctl reboot # shutdown -r now
A second method to setup a CentOS 7 machine hostname is to manually edit the /etc/hostname file
# nano /etc/hostname
How to clean ubuntu up automatically. Set an alais up in the bash profile:
nano .bashrc
alias clean='sudo apt-get autoremove -y && sudo rm -rf ~/.local/share/Trash/*'
Here is how to quickly Determine which Mysql configuration file is being used
$ which mysqld /usr/sbin/mysqld
$ /usr/sbin/mysqld --verbose --help | grep -A 1 "Default options" Default options are read from the following files in the given order: /etc/mysql/my.cnf ~/.my.cnf /usr/etc/my.cnf
When booting an Azure VM, this error:
304.863321] —[ end Kernel panic – not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
Solution: remove old linux kernels, your /boot drive is out of space.
-boot to grub and click on “Advanced options”
-Select a previous kernel (should boot fine)
login and enter command
$ df
See if your /boot directory is 100% used
Remove old linux kernels
$ sudo apt-get autoremove
Also, there may be an issue with the storage drivers (that should be built into initramfs) needed for Hyper-V / Azure.
Other Information: https://support.microsoft.com/en-us/help/4091524/how-recovery-azure-linux-vm-from-kernel-related-boot-related-issues
https://docs.plesk.com/en-US/onyx/advanced-administration-guide-linux/65871/
The Zabbix plugin actively sends information to a Zabbix server like:
Ceph status
I/O operations
I/O bandwidth
OSD status
Storage utilization