Justin's questions

The company I'm currently working for has a script that runs at night that takes a MySQL dump of the production environment and imports it into the staging environment. This is a very basic setup - No replication, no fancy backup or migration utilities. Literally just a mysqldump and import.

Were occasionally running into issues with discrepancies in the data. Upon looking for some solutions to verify the data integrity, I found the CHECKSUM TABLE command.

If I wanted to use the CHECKSUM TABLE, when should it be ran on the server? Before or after the mysqldump? Or is it a bad idea to use rely on the checksum if the backup was taken while the table wasn't locked? The origin of the data is the active production mysql server. So id like to find a way to confirm data integrity without locking the tables in the production database, if possible.

Thank you

I'm having some issues setting up Let's Encrypt for a couple websites that are setup on two different servers, and have the traffic distributed to them via HAProxy.

The servers have a number VHosts/domains on them, all of which are going to need SSL certificates. For the sake of this post, lets say they're:

1. foo.some-site.com
2. bar.some-site.com

Both of these A records are setup with two IP addresses. I can verify with nwtools.com or just nslookup that both of the A records foo.some-site.com and bar.some-site.com resolve the same two IP addresses. And I know that Let's Encrypt requires the vhost to have a valid record used so it can do a lookup.

I planned on running the Lets Encrypt setup on both servers for all the vhosts, and it worked fine for one of them, but when I moved onto the second one, I got an error:

[root@server httpd]# /opt/letsencrypt/letsencrypt-auto --apache -d foo.some-site.com
Checking for new version...
Requesting root privileges to run letsencrypt...
   /root/.local/share/letsencrypt/bin/letsencrypt --apache -d foo.some-site.com
Failed authorization procedure. foo.some-site.com (tls-sni-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: Failed to connect to host for DVSNI challenge

IMPORTANT NOTES:
 - The following errors were reported by the server:

   Domain: foo.some-site.com
   Type:   connection
   Detail: Failed to connect to host for DVSNI challenge

   To fix these errors, please make sure that your domain name was
   entered correctly and the DNS A record(s) for that domain
   contain(s) the right IP address. Additionally, please check that
   your computer has a publicly routable IP address and that no
   firewalls are preventing the server from communicating with the
   client. If you're using the webroot plugin, you should also verify
   that you are serving files from the webroot path you provided.

Could this possibly be because it's doing a lookup or trying to curl foo.some-site.com, and it may be getting directed to the other server? I'm not sure how that would really matter, since both have the same VHosts on them, unless LetsEncrypt is actually listening for the connection that its making itself...

Whats throwing me off is it worked for one of them just fine (say bar.some-site.com), so why would it work for one site, but fail for another one with the exact same setup?

If anyone knows of a way to get Lets Encrypt setup for the same vhosts on two different servers, the help would be much appreciated!

I needed a good NFS storage cloud in AWS, and since EFS is just in preview mode, I did some research, and GFS looked like it would be the best bet.

Currently, I have two servers that are part of one cluster, each is using an EBS volume for the storage, and I was able to create them just fine, and I can read/write as well. But I think I'm having speed issues.

One of the volumes is shared between two web servers, and it holds the php files, which uses the Laravel framework, so theres a lot of files to install. Checking out the git repo and installing via npm install basically never ends, but if I go to a separate directory (not on NFS), and check out the same repo, it works fine, then I just rsync everything over (which again, takes much longer than I would expect, hours). The directory size of everything checked out is only 255M, so I wouldn't think this would take that long.

I created a 1GB file using dd to see the speed:

# dd if=/dev/zero of=./test.txt bs=1024k count=1000 conv=sync
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 139.762 s, 7.5 MB/s

7.5 MB/s - Thats pretty slow I would think.

Would something like this be improved by adding more resources to the Glusterfs nodes? or adding more nodes to the cluster? Or is there throttling somewhere? I'm somewhat new to AWS, as well as GlusterFS, so any help would be appreciated.

UPDATE

Just an FYI, both instances are t2.micro, and in the us-west-2a AZ

Im a little new to AWS, but I've been a Linux admin/engineer for a while. I had a question regarding AWS DNS setup.

I setup a Hosted Zone inside Route53 so I could configure the servers to use hostnames without having to tweak the /etc/hosts file for every record. I went into the VPC and created the DHCP Option Sets and set the domain I set in the Route 53 Hosted Zone, as well as the nameservers listed there.

That allows me to do the lookups to the servers on my domain, but obviously since I removed the default Nameserver from the DHCP Option Sets, it cant do external lookups.

If I create a Option Set with the default Nameserver, and then the rest from ones assigned to the Domain, that wont work either, it just uses whatever teh first NS entry is in the resolv.conf (which I expected)