How to set up multiple secure (SSL/TLS, Qualys SSL Labs A+) websites using LXD containers

In previous posts we saw how to set up LXD on a DigitalOcean VPS, how to set up LXD on a Scaleway VPS, and how the lifecycle of an LXD container looks like.

In this post, we are going to

  1. Create multiple websites, each in a separate LXD container
  2. Install HAProxy as a TLS Termination Proxy, in an LXD container
  3. Configure HAProxy so that each website is only accessible through TLS
  4. Perform the SSL Server Test so that our websites really get the A+!

In this post, we are not going to install WordPress (or other CMS) on the websites. We keep this post simple as that is material for our next post.

The requirements are

Set up a VPS

We are using DigitalOcean in this example.

do-create-droplet-16041

Ubuntu 16.04.1 LTS was released a few days ago and DigitalOcean changed the Ubuntu default to 16.04.1. This is nice.

We are trying out the smallest droplet in order to figure out how many websites we can squeeze in containers. That is, 512MB RAM on a single virtual CPU core, at only 20GB disk space!

In this example we are not using the new DigitalOcean block storage as at the moment it is available in only two datacentres.

Let’s click on the Create droplet button and the VPS is created!

Initial configuration

We are using DigitalOcean in this HowTo, and we have covered the initial configuration in this previous post.

https://blog.simos.info/trying-out-lxd-containers-on-ubuntu-on-digitalocean/

Go through the post and perform the tasks described in section «Set up LXD on DigitalOcean».

Creating the containers

We create three containers for three websites, plus one container for HAProxy.

ubuntu@ubuntu-512mb-ams3-01:~$ lxc init ubuntu:x web1
Creating web1
Retrieving image: 100%
ubuntu@ubuntu-512mb-ams3-01:~$ time lxc init ubuntu:x web2
Creating web2

real    0m6.620s
user    0m0.016s
sys    0m0.004s
ubuntu@ubuntu-512mb-ams3-01:~$ time lxc init ubuntu:x web3
Creating web3

real    1m15.723s
user    0m0.012s
sys    0m0.020s
ubuntu@ubuntu-512mb-ams3-01:~$ time lxc init ubuntu:x haproxy
Creating haproxy

real    0m48.747s
user    0m0.012s
sys    0m0.012s
ubuntu@ubuntu-512mb-ams3-01:~$

Normally it takes a few seconds for a new container to initialize. Remember that we are squeezing here, it’s a 512MB VPS, and the ZFS pool is stored on a file (not a block device)! We are looking into the kernel messages of the VPS for lines similar to «Out of memory: Kill process 3829 (unsquashfs) score 524 or sacrifice child», which indicate that we reached the memory limit. While preparing this blog post, there were a couple of Out of memory kills, so I made sure that nothing critical was dying. If this is too much for you, you can select a 1GB RAM (or more) VPS and start over.

Let’s start the containers up!

ubuntu@ubuntu-512mb-ams3-01:~$ lxc start web1 web2 web3 haproxy
ubuntu@ubuntu-512mb-ams3-01:~$ lxc list
+---------+---------+-----------------------+------+------------+-----------+
|  NAME   |  STATE  |         IPV4          | IPV6 |    TYPE    | SNAPSHOTS |
+---------+---------+-----------------------+------+------------+-----------+
| haproxy | RUNNING | 10.234.150.39 (eth0)  |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web1    | RUNNING | 10.234.150.169 (eth0) |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web2    | RUNNING | 10.234.150.119 (eth0) |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web3    | RUNNING | 10.234.150.51 (eth0)  |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
ubuntu@ubuntu-512mb-ams3-01:~$

You may need to run lxc list a few times until you make sure that all containers got an IP address. That means that they all completed their startup.

DNS configuration

The public IP address of this specific VPS is 188.166.10.229. For this test, I am using the domain ubuntugreece.xyz as follows:

  1. Container web1: ubuntugreece.xyz and www.ubuntugreece.xyz have IP 188.166.10.229
  2. Container web2: web2.ubuntugreece.xyz has IP 188.166.10.229
  3. Container web3: web3.ubuntugreece.xyz has IP 188.166.10.229

Here is how it looks when configured on a DNS management console,

namecheap-configuration-containers

From here and forward, it is a waiting game until these DNS configurations are propagated to the rest of the Internet. We need to wait until those hostnames resolve into their IP address.

ubuntu@ubuntu-512mb-ams3-01:~$ host ubuntugreece.xyz
ubuntugreece.xyz has address 188.166.10.229
ubuntu@ubuntu-512mb-ams3-01:~$ host web2.ubuntugreece.xyz
Host web2.ubuntugreece.xyz not found: 3(NXDOMAIN)
ubuntu@ubuntu-512mb-ams3-01:~$ host web3.ubuntugreece.xyz
web3.ubuntugreece.xyz has address 188.166.10.229
ubuntu@ubuntu-512mb-ams3-01:~$

These are the results after ten minutes. ubuntugreece.xyz and web3.ubuntugreece.xyz are resolving fine, while web2.ubuntugreece.xyz needs a bit more time.

We can continue! (and ignore for now web2)

Web server configuration

Let’s see the configuration for web1. You must repeat the following for web2 and web3.

We install the nginx web server,

ubuntu@ubuntu-512mb-ams3-01:~$ lxc exec web1 — /bin/bash
root@web1:~# apt update
Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]

3 packages can be upgraded. Run ‘apt list –upgradable’ to see them.
root@web1:~# apt upgrade
Reading package lists… Done

Processing triggers for initramfs-tools (0.122ubuntu8.1) …
root@web1:~# apt install nginx
Reading package lists… Done

Processing triggers for ufw (0.35-0ubuntu2) …
root@web1:~#

nginx needs to be configured so that it understands the domain name for web1. Here is the diff,

diff --git a/etc/nginx/sites-available/default b/etc/nginx/sites-available/default
index a761605..b2cea8f 100644
--- a/etc/nginx/sites-available/default
+++ b/etc/nginx/sites-available/default
@@ -38,7 +38,7 @@ server {
        # Add index.php to the list if you are using PHP
        index index.html index.htm index.nginx-debian.html;
 
-       server_name _;
+       server_name ubuntugreece.xyz www.ubuntugreece.xyz;
 
        location / {
                # First attempt to serve request as file, then

and finally we restart nginx and exit the web1 container,

root@web1:/etc/nginx/sites-enabled# systemctl restart nginx
root@web1:/etc/nginx/sites-enabled# exit
exit
ubuntu@ubuntu-512mb-ams3-01:~$

Forwarding connections to the HAProxy container

We are about the set up the HAProxy container. Let’s add iptables rules to perform the forwarding of connections to ports 80 and 443 on the VPS, to the HAProxy container.

ubuntu@ubuntu-512mb-ams3-01:~$ ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 04:01:36:50:00:01  
          inet addr:188.166.10.229  Bcast:188.166.63.255  Mask:255.255.192.0
          inet6 addr: fe80::601:36ff:fe50:1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:40513 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26362 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:360767509 (360.7 MB)  TX bytes:3863846 (3.8 MB)

ubuntu@ubuntu-512mb-ams3-01:~$ lxc list
+---------+---------+-----------------------+------+------------+-----------+
|  NAME   |  STATE  |         IPV4          | IPV6 |    TYPE    | SNAPSHOTS |
+---------+---------+-----------------------+------+------------+-----------+
| haproxy | RUNNING | 10.234.150.39 (eth0)  |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web1    | RUNNING | 10.234.150.169 (eth0) |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web2    | RUNNING | 10.234.150.119 (eth0) |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
| web3    | RUNNING | 10.234.150.51 (eth0)  |      | PERSISTENT | 0         |
+---------+---------+-----------------------+------+------------+-----------+
ubuntu@ubuntu-512mb-ams3-01:~$ sudo iptables -t nat -I PREROUTING -i eth0 -p TCP -d 188.166.10.229/32 --dport 80 -j DNAT --to-destination 10.234.150.39:80
[sudo] password for ubuntu: 
ubuntu@ubuntu-512mb-ams3-01:~$ sudo iptables -t nat -I PREROUTING -i eth0 -p TCP -d 188.166.10.229/32 --dport 443 -j DNAT --to-destination 10.234.150.39:443
ubuntu@ubuntu-512mb-ams3-01:~$

If you want to make those changes permanent, see Saving Iptables Firewall Rules Permanently (the part about the package iptables-persistent).

HAProxy initial configuration

Let’s see how to configure HAProxy in container haproxy. We enter the container, update the software and install the haproxy package.

ubuntu@ubuntu-512mb-ams3-01:~$ lxc exec haproxy -- /bin/bash
root@haproxy:~# apt update
Hit:1 http://archive.ubuntu.com/ubuntu xenial InRelease
...
3 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@haproxy:~# apt upgrade
Reading package lists... Done
...
Processing triggers for initramfs-tools (0.122ubuntu8.1) ...
root@haproxy:~# apt install haproxy
Reading package lists... Done
...
Processing triggers for ureadahead (0.100.0-19) ...
root@haproxy:~#

We add the following configuration to /etc/haproxy/haproxy.conf. Initially, we do not have any certificates for TLS, but we need the Web servers to work with plain HTTP in order for Let’s Encrypt to be able to verify we own the websites. Therefore, here is the complete configuration, with two lines commented out (they start with ###) so that HTTP can work. As soon as we deal with Let’s Encrypt, we go full TLS (by uncommenting the two lines that start with ###) and never look back. We mention when to uncomment later in the post.

diff --git a/etc/haproxy/haproxy.cfg b/etc/haproxy/haproxy.cfg
index 86da67d..f6f2577 100644
--- a/etc/haproxy/haproxy.cfg
+++ b/etc/haproxy/haproxy.cfg
@@ -18,11 +18,17 @@ global
     ssl-default-bind-ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS
     ssl-default-bind-options no-sslv3
 
+        # Minimum DH ephemeral key size. Otherwise, this size would drop to 1024.
+        # @link: https://cbonte.github.io/haproxy-dconv/configuration-1.5.html#3.2-tune.ssl.default-dh-param
+        tune.ssl.default-dh-param 2048
+
 defaults
     log    global
     mode    http
     option    httplog
     option    dontlognull
+        option  forwardfor
+        option  http-server-close
         timeout connect 5000
         timeout client  50000
         timeout server  50000
@@ -33,3 +39,56 @@ defaults
     errorfile 502 /etc/haproxy/errors/502.http
     errorfile 503 /etc/haproxy/errors/503.http
     errorfile 504 /etc/haproxy/errors/504.http
+
+# Configuration of the frontend (HAProxy as a TLS Termination Proxy)
+frontend www_frontend
+    # We bind on port 80 (http) but (see below) get HAProxy to force-switch to HTTPS.
+    bind *:80
+    # We bind on port 443 (https) and specify a directory with the certificates.
+####    bind *:443 ssl crt /etc/haproxy/certs/
+    # We get HAProxy to force-switch to HTTPS, if the connection was just HTTP.
+####    redirect scheme https if !{ ssl_fc }
+    # TLS terminates at HAProxy, the container runs in plain HTTP. Here, HAProxy informs nginx
+    # that there was a TLS Termination Proxy. Required for WordPress and other CMS.
+    reqadd X-Forwarded-Proto:\ https
+
+    # Distinguish between secure and insecure requestsa (used in next two lines)
+    acl secure dst_port eq 443
+
+    # Mark all cookies as secure if sent over SSL
+    rsprep ^Set-Cookie:\ (.*) Set-Cookie:\ \1;\ Secure if secure
+
+    # Add the HSTS header with a 1 year max-age
+    rspadd Strict-Transport-Security:\ max-age=31536000 if secure
+
+    # Configuration for each virtual host (uses Server Name Indication, SNI)
+    acl host_ubuntugreece_xyz hdr(host) -i ubuntugreece.xyz www.ubuntugreece.xyz
+    acl host_web2_ubuntugreece_xyz hdr(host) -i web2.ubuntugreece.xyz
+    acl host_web3_ubuntugreece_xyz hdr(host) -i web3.ubuntugreece.xyz
+
+    # Directing the connection to the correct LXD container
+    use_backend web1_cluster if host_ubuntugreece_xyz
+    use_backend web2_cluster if host_web2_ubuntugreece_xyz
+    use_backend web3_cluster if host_web3_ubuntugreece_xyz
+
+# Configuration of the backend (HAProxy as a TLS Termination Proxy)
+backend web1_cluster
+    balance leastconn
+    # We set the X-Client-IP HTTP header. This is usefull if we want the web server to know the real client IP.
+    http-request set-header X-Client-IP %[src]
+    # This backend, named here "web1", directs to container "web1.lxd" (hostname).
+    server web1 web1.lxd:80 check
+
+backend web2_cluster
+    balance leastconn
+    # We set the X-Client-IP HTTP header. This is usefull if we want the web server to know the real client IP.
+    http-request set-header X-Client-IP %[src]
+    # This backend, named here "web2", directs to container "web2.lxd" (hostname).
+    server web2 web2.lxd:80 check
+
+backend web3_cluster
+    balance leastconn
+    # We set the X-Client-IP HTTP header. This is usefull if we want the web server to know the real client IP.
+    http-request set-header X-Client-IP %[src]
+    # This backend, named here "web3", directs to container "web3.lxd" (hostname).
+    server web3 web3.lxd:80 check

Let’s restart HAProxy. If you get any errors, run systemctl status haproxy and try to figure out what went wrong.

root@haproxy:~# systemctl restart haproxy
root@haproxy:~# exit
ubuntu@ubuntu-512mb-ams3-01:~$

Does it work? Let’s visit the website,

do-ubuntugreece

It’s is working! Let’s Encrypt will be able to access and verify that we own the domain in the next step.

Get certificates from Let’s Encrypt

We exit out to the VPS and install letsencrypt.

ubuntu@ubuntu-512mb-ams3-01:~$ sudo apt install letsencrypt
[sudo] password for ubuntu: 
Reading package lists... Done
...
Setting up python-pyicu (1.9.2-2build1) ...
ubuntu@ubuntu-512mb-ams3-01:~$

We run letsencrypt three times, one for each website. update It is also possible to simplify the following by using multiple domain (or Subject Alternative Names (SAN)) certificates. Thanks for @jack who mentioned this in the comments.

ubuntu@ubuntu-512mb-ams3-01:~$ sudo letsencrypt certonly --authenticator webroot --webroot-path=/var/lib/lxd/containers/web1/rootfs/var/www/html -d ubuntugreece.xyz -d www.ubuntugreece.xyz
... they ask for a contact e-mail address and whether we accept the Terms of Service...

IMPORTANT NOTES:
 - If you lose your account credentials, you can recover through
   e-mails sent to xxxxx@gmail.com.
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/ubuntugreece.xyz/fullchain.pem. Your cert
   will expire on 2016-10-21. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.
 - Your account credentials have been saved in your Let's Encrypt
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Let's
   Encrypt so making regular backups of this folder is ideal.
 - If you like Let's Encrypt, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

ubuntu@ubuntu-512mb-ams3-01:~$

For completeness, here are the command lines for the other two websites,

ubuntu@ubuntu-512mb-ams3-01:~$ sudo letsencrypt certonly --authenticator webroot --webroot-path=/var/lib/lxd/containers/web2/rootfs/var/www/html -d web2.ubuntugreece.xyz

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/web2.ubuntugreece.xyz/fullchain.pem. Your
   cert will expire on 2016-10-21. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.
 - If you like Let's Encrypt, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

ubuntu@ubuntu-512mb-ams3-01:~$ time sudo letsencrypt certonly --authenticator webroot --webroot-path=/var/lib/lxd/containers/web3/rootfs/var/www/html -d web3.ubuntugreece.xyz

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/web3.ubuntugreece.xyz/fullchain.pem. Your
   cert will expire on 2016-10-21. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.
 - If you like Let's Encrypt, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le


real    0m18.458s
user    0m0.852s
sys    0m0.172s
ubuntu@ubuntu-512mb-ams3-01:~$

Yeah, it takes only around twenty seconds to get your Let’s Encrypt certificate!

We got the certificates, now we need to prepare them so that HAProxy (our TLS Termination Proxy) can make use of them. We just need to join together the certificate chain and the private key for each certificate, and place them in the haproxy container at the appropriate directory.

ubuntu@ubuntu-512mb-ams3-01:~$ sudo mkdir /var/lib/lxd/containers/haproxy/rootfs/etc/haproxy/certs/
ubuntu@ubuntu-512mb-ams3-01:~$ DOMAIN='ubuntugreece.xyz' sudo -E bash -c 'cat /etc/letsencrypt/live/$DOMAIN/fullchain.pem /etc/letsencrypt/live/$DOMAIN/privkey.pem > /var/lib/lxd/containers/haproxy/rootfs/etc/haproxy/certs/$DOMAIN.pem'
ubuntu@ubuntu-512mb-ams3-01:~$ DOMAIN='web2.ubuntugreece.xyz' sudo -E bash -c 'cat /etc/letsencrypt/live/$DOMAIN/fullchain.pem /etc/letsencrypt/live/$DOMAIN/privkey.pem > /var/lib/lxd/containers/haproxy/rootfs/etc/haproxy/certs/$DOMAIN.pem'
ubuntu@ubuntu-512mb-ams3-01:~$ DOMAIN='web3.ubuntugreece.xyz' sudo -E bash -c 'cat /etc/letsencrypt/live/$DOMAIN/fullchain.pem /etc/letsencrypt/live/$DOMAIN/privkey.pem > /var/lib/lxd/containers/haproxy/rootfs/etc/haproxy/certs/$DOMAIN.pem'
ubuntu@ubuntu-512mb-ams3-01:~$

HAProxy final configuration

We are almost there. We need to enter the haproxy container and uncomment those two lines (those that started with ###) that will enable HAProxy to work as a TLS Termination Proxy. Then, restart the haproxy service.

ubuntu@ubuntu-512mb-ams3-01:~$ lxc exec haproxy bash
root@haproxy:~# vi /etc/haproxy/haproxy.cfg 

haproxy-config-ok
root@haproxy:/etc/haproxy# systemctl restart haproxy
root@haproxy:/etc/haproxy# exit
ubuntu@ubuntu-512mb-ams3-01:~$

Let’s test them!

Here are the three websites, notice the padlocks on all three of them,

The SSL Server Report (Qualys)

Here are the SSL Server Reports for each website,

You can check the cached reports for LXD container web1, LXD container web2 and LXD container web3.

Results

The disk space requirements for those four containers (three static websites plus haproxy) are

ubuntu@ubuntu-512mb-ams3-01:~$ sudo zpool list
[sudo] password for ubuntu: 
NAME         SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
mypool-lxd  14.9G  1.13G  13.7G         -     4%     7%  1.00x  ONLINE  -
ubuntu@ubuntu-512mb-ams3-01:~$

The four containers required a bit over 1GB of disk space.

The biggest concern has been the limited RAM memory of 512MB. The Out Of Memory (OOM) handler was invoked a few times during the first steps of container creation, but not afterwards during the launching of the nginx instances.

ubuntu@ubuntu-512mb-ams3-01:~$ dmesg | grep "Out of memory"
[  181.976117] Out of memory: Kill process 3829 (unsquashfs) score 524 or sacrifice child
[  183.792372] Out of memory: Kill process 3834 (unsquashfs) score 525 or sacrifice child
[  190.332834] Out of memory: Kill process 3831 (unsquashfs) score 525 or sacrifice child
[  848.834570] Out of memory: Kill process 6378 (localedef) score 134 or sacrifice child
[  860.833991] Out of memory: Kill process 6400 (localedef) score 143 or sacrifice child
[  878.837410] Out of memory: Kill process 6436 (localedef) score 151 or sacrifice child
ubuntu@ubuntu-512mb-ams3-01:~$

There was an error while creating one of the containers in the beginning. I repeated the creation command and it completed successfully. That error was probably related to this unsquashfs kill.

Summary

We set up a $5 VPS (512MB RAM, 1CPU core and 20GB SSD disk) with Ubuntu 16.04.1 LTS, then configured LXD to handle containers.

We created three containers for three static websites, and an additional container for HAProxy to work as a TLS Termination Proxy.

We got certificates for those three websites, and verified that they all pass with A+ at the Qualys SSL Server Report.

The 512MB RAM VPS should be OK for a few low traffic websites, especially those generated by static site generators.

 

11 comments

  • jack

    It looks like you have all three web servers on one machine. In this case it is not need to create three Let’s Encrypt certificates. You could create one certificate and have other domains in Certificate Alternative Name. Like:
    sudo letsencrypt certonly –authenticator webroot –webroot-path=/var/lib/lxd/containers/web3/rootfs/var/www/html -d http://www.ubuntugreece.xyz -d web3.ubuntugreece.xyz -d web2.ubuntugreece.xyz

    In above case one certificate is created which is valid for the following three domains:
    http://www.ubuntugreece.xyz
    web2.ubuntugreece.xyz
    web3.ubuntugreece.xyz

  • Simos Xenitellis

    @jack:

    Indeed, you can create a certificate with up to 100 domains with Let’s Encrypt.
    My attempt has been to show the process of creating certificates with different domains; I did not have handy different domains so I resorted showing this with subdomains only.

  • jack

    @Simos, I don’t want to go too deep, because this certificate section was not main point of the article. But if someone wants it is possible to have one certificate for entirely different domains and my suggestion above is not restricted to subdomains.

  • Simos Xenitellis

    @jack, Thanks for persisting. I did not know that LetsEncrypt had that feature.

    They use the terminology “multi-domain/multiple domain” certificates or “Subject Alternative Names (SAN)” certificates, the term you mentioned earlier. As in https://www.digicert.com/subject-alternative-name.htm

    There is a reference for those “multi-domain” certificates at some community threads like https://community.letsencrypt.org/t/please-support-multi-domain-ssl-certificates-like-the-ones-on-positivessl/867/2
    Apparently, they are easy to confuse with wildcard certificates.

    The LetsEncrypt FAQ actually mentions them:

    “Can I get a certificate for multiple domain names (SAN certificates)?

    Yes, the same certificate can apply to several different names using the Subject Alternative Name (SAN) mechanism. The resulting certificates will be accepted by browsers for any of the domain names listed in them.”
    Source: https://letsencrypt.org/docs/faq/

  • David Goodwin

    You could use cgroups (through lxc) to limit the resources each site has – this might help protect you from the OOMing on the host – or at least stop one container from taking down the server.

    Alternatively see if you can add a large swap file?

  • Simos Xenitellis

    @Davis Goodwin:

    In this specific installation, the OOM handler was invoked for processes (unsquashfs, localedef) running in the VPS and not in a container.
    The containers did not run something memory-intensive like mysql, so once the containers were started, they were running fine for sharing static content.
    I did not run any benchmarks for these web servers and it’s something that I should do for a future post.
    I think it would be better to let them all share the VPS memory as needed, without restrictions, so that any spike in traffic to one site can be handled better (by using up more memory).

    An alternative could be to try out another rootfs instead of “ubuntu:x” (something from “images:”). A few MB should be shaved off from each running container. It would be interesting to measure the memory usage in these scenarios.

    The addition of a swap file should help. There is an article about that at https://www.digitalocean.com/community/tutorials/how-to-add-swap-space-on-ubuntu-16-04 with a note about deciding whether to actually use it.

Leave a Reply

%d bloggers like this: