IMB's questions

Trying to run firewalld on a fresh AlmaLinux 9 VPS (OpenVZ). Only did the ff. so far:

dnf upgrade
systemctl start firewalld
systemctl enable firewalld
systemctl status firewalld

I am immediately greeted with these errors:

Oct 26 06:58:14 myserver firewalld[1097]: ERROR: '/usr/sbin/iptables -w10 -t mangle -X' failed: iptables v1.8.7 (nf_tables):  CHAIN_USER_DEL failed (Device or resource busy): chain POSTROUTING_direct
Oct 26 06:58:15 myserver firewalld[793]: ERROR: '/usr/sbin/iptables -w10 -t nat -A PREROUTING -j PREROUTING_direct' failed: iptables v1.8.7 (nf_tables):  CHAIN_ADD failed (No such file or directory): chain PREROUTING
Oct 26 06:58:16 myserver firewalld[793]: ERROR: '/usr/sbin/iptables -w10 -t nat -A PREROUTING -j PREROUTING_direct' failed: iptables v1.8.7 (nf_tables):  CHAIN_ADD failed (No such file or directory): chain PREROUTING
Oct 26 06:58:17 myserver firewalld[1097]: ERROR: '/usr/sbin/ip6tables -w10 -t raw -X' failed: ip6tables v1.8.7 (nf_tables):  CHAIN_USER_DEL failed (Device or resource busy): chain PREROUTING_direct
Oct 26 06:58:17 myserver firewalld[1097]: ERROR: '/usr/sbin/ip6tables -w10 -t raw -X' failed: ip6tables v1.8.7 (nf_tables):  CHAIN_USER_DEL failed (Device or resource busy): chain PREROUTING_direct
Oct 26 06:58:18 myserver firewalld[793]: ERROR: '/usr/sbin/ip6tables -w10 -t nat -A PREROUTING -j PREROUTING_direct' failed: ip6tables v1.8.7 (nf_tables):  CHAIN_ADD failed (No such file or directory): chain PREROUTING
Oct 26 06:58:20 myserver firewalld[793]: ERROR: '/usr/sbin/ip6tables -w10 -t nat -A PREROUTING -j PREROUTING_direct' failed: ip6tables v1.8.7 (nf_tables):  CHAIN_ADD failed (No such file or directory): chain PREROUTING
Oct 26 06:58:20 myserver firewalld[1097]: ERROR: COMMAND_FAILED: '/usr/sbin/iptables -w10 -t mangle -X' failed: iptables v1.8.7 (nf_tables):  CHAIN_USER_DEL failed (Device or resource busy): chain POSTROUTING_direct
Oct 26 06:58:23 myserver firewalld[793]: ERROR: COMMAND_FAILED: '/usr/sbin/ip6tables -w10 -t nat -A PREROUTING -j PREROUTING_direct' failed: ip6tables v1.8.7 (nf_tables):  CHAIN_ADD failed (No such file or directory): chain PREROUTING

Any ideas?

Say you have the ff. email server:

server1.com has the mailbox [email protected]

server2.com has the mailbox [email protected]

If the MX priority settings are:

Priority: 0
Destination: server1.com

Priority: 10
Destination: server2.com

Will sending an email to [email protected] eventually arrive at server2.com or will it fail immediately because it doesn't exist in server1.com?

I have this line in /etc/apache2/mods-enabled/ssl.conf

SSLProtocol -all +TLSv1.2

However SSL checker whynopadlock still shows this:

Any ideas on how to completely disable TLSv1 in Apache 2.4 (Debian 8) ?

Our email is being spoofed. We already have SPF/DKIM/DMARC p="quarantine" policies in place however we are still receiving thousands of Non-Delivery Receipt (NDR) in our inbox.

Will changing to DMARC p="reject" prevent NDR backscatter?

Any other advice how to prevent NDR backscatter?

Note: We are using OpenSRS hosted email.

Possible Duplicate:
How do you do Load Testing and Capacity Planning for Web Sites

I've seen tutorials saying they can run decent websites on 64MB RAM (Debian/Lighttpd/PHP/MySQL) however it's not clearly defined how much hits/traffic a "decent" site gets.

Is there a rule of thumb on how much RAM a web server needs? To keep things simple, let's say you're running a site with static content and it's averaging at 100,000 hits per hour (HTML + images combined, no MySQL). How much RAM is the minimum requirement for that?

As a followup question to his very popular question: Why is DNS failover not recommended?, I think it was agreed that DNS failover is not 100% reliable due to caching.

However the highest voted answer did not really discuss what is the better solution to achieve failover between two different data centers. The only solution presented was local load balancing (single data center).

So my question is quite simply what is the real solution to cross data center failover?

Does it still make sense to setup your own failover system (HAproxy + 2 or more servers for example) when self healing cloud seems like a practical solution? They seem to do the same job or am I missing something?

I'm looking to setup an email server which can accommodate hundreds of accounts with "unlimited" email space. I understand that there is no such thing as unlimited but I am under the impression I can RAID several disks (or a bunch servers) as I go.

To demonstrate my need: I could start with a single server with 500GB space now I need provisions or a plan for additional x number of 500GBs drives in the future (all seen as one big drive). I do not know how to properly do this or if this is the best approach to my goal. Your advice will be very much appreciated.

To put simply: How do I best handle expected email storage expansion in the future?

Ever since I bought a VPS, I have been receiving emails like those shown below since day one, every single day. I was wondering if is this really normal? Is there anyway I can prevent it, or is CSF/LFD pretty much my best defense already?

Possible Duplicate:
How long does it take for an A record to propagate?

I recently changed nameservers and it has been 24 hours since. Some of my visitors are complaining they are still viewing the old site while some are already seeing the new site. Is there any way to speed-up the DNS propagation without updating the hosts file of each of my visitors?

Are there any best practices when it comes to changing nameservers to minimize this problem?

Note: This is a follow-up to my previous question regarding DNS Failover.

The Goal: to make the client's web browser select the next available server if one is down instantly.

I've read somewhere that multiple A records (while not the best solution) is the only "instant failover" solution possible for HTTP/browser-based applications.

Here's the scenario/example:

I have two servers A and B which contains exactly the same content. The IP address of server A is 1.1.1.1 and 1.1.1.2 The IP address of server B is 2.2.2.1 and 2.2.2.2 I have a domain registered at Godaddy. If I want to make use of DNS round robin, which method is best?

Method 1: Do I set my nameserver entries at Godaddy like this?

1. ns1.serverA.com
2. ns2.serverA.com
3. ns1.serverB.com
4. ns2.serverB.com

Method 2: Or do I make Godaddy as my nameserver and add A Records like this:

1. A @ 1.1.1.1
2. A @ 1.1.1.2
3. A @ 2.2.2.1
4. A @ 2.2.2.2

My question is, will DNS round robin work with either of the two methods? If not then what's the best method to achieve the goal?

I've been reading about DNS failovers and a bunch of other technical terms however I'm a bit of a newbie in this so it all sounds Greek to me. Basically here's what I just need:

I have two shared hosting accounts from two different providers (Server A and Server B). Each of this accounts contain exactly the same website content.

On a normal day, typing my domain name should point to the IP of Server A. But on a bad day in which Server A is down or unreachable, my domain name should point to the IP of Server B in the fastest way possible.

How do you achieve this and what services can you recommend if any? Thanks.

Note: this question has a follow-up question: DNS Round Robin: Multiple Nameservers VS Multiple A Records?