Zumo de Vidrio's questions

I have 2 servers with postfix.

ServerA with this main.cf:

relayhost = smtp.public.com:587
smtp_use_tls=yes
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/smarthost_passwd
smtp_sasl_security_options =

Sending emails locally from server A works fine, it does properly the relay over the public smtp and the message arrives to the destination

Now I want to configure ServerB so that when I send an email from it, it will go directly to ServerA which should send the email through the public smtp server (as it does when sending from ServerA by itself)

Telnet from ServerB to ServerA on port 25 is working.

How can I perform this configuration ? I'm not even able to find the correct words for googling it.

EDIT

It worked after following the validated answer.

In case of this can be useful for someone else, these are the configuration files that I finally used:

ServerA:

main.cf:

relayhost = <IP/domain SMTP externe>:<port>
smtp_use_tls=yes
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/smarthost_passwd
smtp_sasl_security_options =
mynetworks = <Net of ServerB>

/etc/postfix/smarthost_passwd:

<IP/domain SMTP externe>:<port>     <user>:<pass>

ServerB:

main.cf:

relayhost = <hostname_ServerA>:<port>
smtp_use_tls=yes
smtp_sasl_auth_enable = no
smtp_sasl_security_options =

I have an Ubuntu 16.04 with the following NTP configuration:

driftfile /var/lib/ntp/drift

restrict -4 default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

restrict 127.0.0.1 nomodify notrap
restrict 10.0.200.15 mask 255.255.255.0 nomodify notrap

server 127.127.1.0
fudge 127.127.1.0 stratum 10

server 0.ntp.pool.org iburst prefer minpoll 4 maxpoll 7
server 1.ntp.pool.org iburst prefer minpoll 4 maxpoll 7
server 2.ntp.pool.org iburst prefer minpoll 4 maxpoll 7
tinker panic 0

restrict 127.0.0.1
restrict -6 ::1

But it is always synchronizing with localhost (I think it is because the lower stratum value):

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 127.127.1.0     .LOCL.          10 l  16h   64    0    0.000    0.000   0.000
 64.99.80.121    .STEP.          16 u    -  128    0    0.000    0.000   0.000

However I want it to synchronize with the external NTP ntp.pool.org

I have added the ubuntu ntp server to the ntp.conf file:

server ntp.ubuntu.com iburst prefer minpoll 4 maxpoll 7

And now I see that it has a stratum 2 and the ntp is able to synchronize to it:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 127.127.1.0     .LOCL.          10 l  16h   64    0    0.000    0.000   0.000
 64.99.80.121    .STEP.          16 u    -  128    0    0.000    0.000   0.000
*91.189.91.157   194.58.200.20    2 u   15  128  377   79.191    0.042   1.964

The ntptrace gives timeout for both servers:

$ ntptrace ntp.ubuntu.com
ntp.ubuntu.com: timed out, nothing received
***Request timed out

$ ntptrace ntp.pool.org
ntp.pool.org: timed out, nothing received
***Request timed out

Am I missing some configuration to be able to synchronize only with ntp.pool.org?

I have checked the answers here but I'm not finding an answer for my case

UPDATE

This VM will act as ntp server for another VMs.

Query results:

ntpdate -q ntp.pool.org
server 64.99.80.121, stratum 0, offset 0.000000, delay 0.00000
26 Nov 14:34:37 ntpdate[4577]: no server suitable for synchronization found

ntpdate -q ntp.ubuntu.com
server 91.189.94.4, stratum 2, offset 0.000290, delay 0.03615
server 91.189.89.199, stratum 2, offset 0.000654, delay 0.03668
server 91.189.89.198, stratum 2, offset -0.000251, delay 0.03674
server 91.189.91.157, stratum 2, offset 0.000159, delay 0.10548
26 Nov 14:36:15 ntpdate[4585]: adjust time server 91.189.94.4 offset 0.000290 sec

I have found in ntp documentation that stratum 16 indicates some problems with the ntp server. Can we conclude that ntp.pool.org is not working ?

Due to limitations in physical ressources, I need to know if is it possible to declare the same host as manager and node at the same time?

I can't find anything in the official documentation. In case of it is technically possible, is that a good practice? Could it cause any problems?

I have a service web running in the url service.old_domain.com (hosted in an internal DNS service)

Now I want to do a redirection from the url service.new_domain.com (hosted in an external DNS service)

Is it enough with adding a CNAME in the external DNS service like:

service.new_domain.com -> service.old_domain.com

Or shall I add a type A like:

service.new_domain.com -> IP address of "service.old_domain.com"

I am running multiple redmine instances over docker where the web requests are handled with docker flow proxy ACL's so that every ACL is performing the link between the name of the running docker container with its domain as configured in the file haproxy.cfg

My question is if it is possible to point 2 different domains to the same redmine instance. I have been looking in the docker flow proxy configuration but I'm not able to find the answer.

Is it possible to define a database pool value in order to decrease the database connections sent from zabbix server?

I saw a method when it was done through apache mod_fcgid, Shall it be done with mod mpm_prefork as well?

By doing tests (with only 2 users connected through web gui), I found 60 outgoing connections to database server when my limit in database server was 100, 23 when my limit was 20 (of course it didn't work) and with limit 30 I have 29 outgoing connections, Why such difference?

It seems to me that somehow, zabbix is able to identify the maximum number of database connections to create outgoing connections, but honestly that's a little strange for me, Zabbix seems to abuse of resources when I increase the pool in database server.

The scenario is a shared PostgreSQL server, that's why increasing pools in database server side is not a good idea in my case.

Zabbix is installed in a CentOS 7 server.

Environment: 5 apache instances (balancerX) which distribute the traffic among 3 application servers (serverX).

With mod_balancer configuration by request with same loadfactor, server1 has a huge load while the other ones are having less load, that's why the balancer configuration is applied in the same way to all the servers no matter the real load of them, so always the first connection to balancer1,2,3,4 or 5 is redirected to server1. Since users are assigned the balancers randomly due to a HW balancer (that unfortunately can't be managed), I can't control that the 3 servers are receiving the same amount of connections.

How can I configure it to have the same load on server1,2 and 3?

Schema:

Balancer1   Balancer2   Balancer3   Balancer4   Balancer5
---------   ---------   ---------   ---------   ---------
Server1     Server1     Server1     Server1     Server1
Server2     Server2     Server2     Server2     Server2
Server3     Server3     Server3     Server3     Server3