list mysql connections

lsof -nPi :3306

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
mysqld 5748 mysql 20u IPv4 19843 0t0 TCP *:3306 (LISTEN)
mysqld 5748 mysql 132u IPv4 24831149 0t0 TCP 10.50.124.17:3306->172.31.24.12:51908
mysqld 5748 mysql 163u IPv4 24831150 0t0 TCP 10.50.124.17:3306->172.31.24.12:51909
mysqld 5748 mysql 169u IPv4 24831446 0t0 TCP 10.50.124.17:3306->172.31.24.11:56843
mysqld 5748 mysql 193u IPv4 24831447 0t0 TCP 10.50.124.17:3306->172.31.24.11:56844
mysqld 5748 mysql 198u IPv4 24831448 0t0 TCP 10.50.124.17:3306->172.31.24.11:56845
mysqld 5748 mysql 265u IPv4 24831404 0t0 TCP 10.50.124.17:3306->172.31.24.12:51917
mysqld 5748 mysql 280u IPv4 24831505 0t0 TCP 10.50.124.17:3306->172.31.24.12:51918

ssh tunnel with key for tunnel only

cat .ssh/authorized_keys

no-pty,no-X11-forwarding,permitopen="10.157.80.133:8090",command="/bin/echo do-not-send-commands" ssh-dss AAAxSEm45jSTIFxSWl+JmeiaOe/re2J6xDQ/PMiKd9VkaVUdg== lunohod@deb

ssh -i /home/lunohod/.ssh/id_dsa lunohod@10.157.0.21 -L 10.10.0.1:8090:10.157.80.133:8090 -N -g #-f

delay pool in squid

Simple delay pool in squid:

# file: /etc/squid/squid.conf

delay_pools 1
delay_class 1 1
delay_access 1 allow all
delay_parameters 1 64000/64000          # 512 kbits == 64 kbytes per second

Mono repo - CentOS

Mono repo - CentOS: download.mono-project.com

How do I use OpenSSL to encrypt files? - bsdsupport.org

Q: How do I use OpenSSL to encrypt files?

Management infrastructure with DNS

You have several tens of servers in data centers in different parts of the world, a few large customers. Different versions of the software and settings for each cluster. This is familiar to many developers and operators. When running with hundreds of servers and network equipment management of the entire infrastructure can be time consuming.

Updating the software taking into account the characteristics of platforms, backup, reaction to incidents, and so on becoming a time consuming process.

To address these challenges ideal configuration management system. Like Chef, Puppet, SaltStack and others. If you are in the company may not use a configuration management system - start.

But in that case, if the infrastructure has been growing for several years. Gradually increase the number of servers. Or for some other reason you do not use the configuration management system. This article talks about how to add structure to your fleet of servers, network equipment and workstations.

Structure

Think about the structure of your company. Which groups of servers perform the same tasks. On what grounds and what groups can merge virtual machines. By type: Dev, Test, Prod. Feature: Vpn-servers, Web-servers, Db-servers. By location: BY, Client-name, Amazon. And so on.

[dev ]     +----+ +------+ +---+
[test] <=> |asia| |docker| |ec2|
[prod]     +----+ +------+ +---+

Then describe the structure and purpose of servers using DNS.
Examples:

vpn1.mts.devel.aptinfo.net
balancer2.us.dev.aptinfo.net
db3.azure.prod.aptinfo.net

app4.vmware.stage.aptinfo.net
sql5.ec2-west.preprod.aptinfo.net
www.aptinfo.net

Try to make the domain name gave the most information about the server as possible.

Convert the DNS structure

From a set of DNS records is easy to get a hierarchical structure.

{
    "domain": "aptinfo.net",
    "records": [
        {
            "content": "10.0.101.223",
            "fqdn": "app1.nl.stage.aptinfo.net",
            "subdomain": "app1.nl.stage",
            "type": "A"
        },
        {
            "content": "10.0.101.224",
            "fqdn": "app2.nl.stage.aptinfo.net",
            "subdomain": "app2.nl.stage",
            "type": "A"
        },

Transform list A, CNAME and other records in an associative array. We separate the domain part and group records by common parts of the subdomain.

'nl.stage': ['app1.nl.stage.aptinfo.net',
             'app2.nl.stage.aptinfo.net',
             'db1.nl.stage.aptinfo.net']

After this easy to get information about a group of servers using commands bash. It is also easy to manage groups of servers using different tools, such as Fabric.

$ fab  -R nl.stage  --  who
[app1.nl.stage.aptinfo.net] Executing task ''
[app1.nl.stage.aptinfo.net] run: who
[app1.nl.stage.aptinfo.net] out: root     pts/1        Jul 23 21:30 (10.50.124.15)
[app1.nl.stage.aptinfo.net] out: 

[app2.nl.stage.aptinfo.net] Executing task ''
[app2.nl.stage.aptinfo.net] run: who
[app2.nl.stage.aptinfo.net] out: root     pts/3        Jul 23 21:30 (10.50.124.15)
[app2.nl.stage.aptinfo.net] out: 

[db1.nl.stage.aptinfo.net] Executing task ''
[db1.nl.stage.aptinfo.net] run: who
No handlers could be found for logger "paramiko.transport"

Fatal error: Error reading SSH protocol banner

Underlying exception:
    Error reading SSH protocol banner

Aborting.
Disconnecting from root@app1.nl.stage.aptinfo.net... done.
Disconnecting from root@app2.nl.stage.aptinfo.net... done.
Error reading SSH protocol banner

Underlying exception:
    Error reading SSH protocol banner

But fabric has disadvantages. First: the program is interrupted if the return code is not equal to 0. The commands Secondly: an interrupt when one of the hosts is not available. For this purpose, more suitable Ansible

$ ansible  us.prod  -i ~/ansible/dynamic.py  -m shell  -a uptime

db2.us.prod.aptinfo.net | success | rc=0 >>
 15:33:38 up 1116 days, 21:55,  2 users,  load average: 0.04, 0.05, 0.07

app2.us.prod.aptinfo.net | success | rc=0 >>
 15:33:46 up 1117 days, 27 min,  2 users,  load average: 0.42, 0.53, 0.53

bckp.us.prod.aptinfo.net | success | rc=0 >>
 15:33:51 up 1152 days, 27 min,  1 user,  load average: 0.08, 0.43, 0.49

app1.us.prod.aptinfo.net | success | rc=0 >>
 15:33:52 up 1006 days,  7:07,  2 users,  load average: 2.19, 2.25, 2.20

Quickly and conveniently.
I hope this article will be useful.

yum throttle

echo throttle=128K >> /etc/yum.conf

man 5 yum.conf