Tuesday 31 August 2021

Munging Dockerfiles using Bash and Jenkins

Whilst trying to mitigate an issue with a Docker image, in order to remediate a pair of CVE: -



I needed to ensure that the latest version of openssl was being used.

Now this image is based, in part, on Alpine Linux, and already included: -

FROM alpine:3.14.1 AS run


RUN apk --no-cache add openssl

which *should* mean that I'd be getting the required version of openssl as advised by the two CVEs, namely: -

OpenSSL 1.1.1l

and yet I was still seeing the issues when scanning the resulting image using IBM Container Registry's Vulnerability Advisor tool.

I even added: -

RUN apk info --all openssl

to the Dockerfile, which returned: -

openssl-1.1.1l-r0 description:
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.14/main: No such file or directory
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.14/community: No such file or directory
Toolkit for Transport Layer Security (TLS)
openssl-1.1.1l-r0 webpage:
openssl-1.1.1l-r0 installed size:
660 KiB
openssl-1.1.1l-r0 depends on:
openssl-1.1.1l-r0 provides:
openssl-1.1.1l-r0 is required by:
openssl-1.1.1l-r0 contains:
openssl-1.1.1l-r0 triggers:
openssl-1.1.1l-r0 has auto-install rule:
openssl-1.1.1l-r0 affects auto-installation of:
openssl-1.1.1l-r0 replaces:
openssl-1.1.1l-r0 license:

After much tinkering, I came to the realisation that there's more to life than just apk add, namely there's a need to (a) update the Alpine repository sources and (b) upgrade Alpine itself ...

In the Ubuntu world, this would achieved by apt get update && apt-get upgrade -y

In the Alpine world, this is achieved by apk update && apk upgrade

Therefore, I amended my Dockerfile from: -

RUN apk --no-cache add openssl

to: -

RUN apk update && apk upgrade && apk --no-cache add openssl

which did the trick

However, because I'm building the image using Jenkins, via a Bash script wrapped up in a Groovy script ( the Jenkinsfile ), I needed to do some escape magic.

I started with this: -

sed -i'' "s/RUN apk \-\-no-cache add openssl/RUN apk update \&\& apk upgrade \&\& apk \-\-no-cache add openssl/g" Dockerfile

but the Jenkins job failed with: -

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 22: unexpected char: '\' @ line 22, column 41.
             sed -i'' "s/RUN apk \-\-no-cac

Now I was going a little bit OTT with the escape characters, as I didn't really need to escape out the hyphens ( - ) but the same problem occurred with this: -

sed -i'' "s/RUN apk --no-cache add openssl/RUN apk update \&\& apk upgrade \&\& apk --no-cache add openssl/g" Dockerfile

because I'd forgotten that escaping in Bash in Groovy has its own set of peculiar rules ...

TL;DR; I needed to double escape ...

sed -i'' "s/RUN apk --no-cache add openssl/RUN apk update \\&\\& apk upgrade \\&\\& apk --no-cache add openssl/g" Dockerfile

With this in place, all is good - the build runs smoothly AND the resulting image is clean and green ...

Friday 20 August 2021

Kata Containers - Building a Pod Sandbox image and QEMU says "No No No"

 As ever, I'm tinkering with Kata 2.0, currently helping a friend build the Pod Sandbox image using the Image Builder tool.

Specifically, the command: -

~/go/src/github.com/kata-containers/kata-containers/tools/osbuilder/image-builder/image_builder.sh ~/fedora_rootfs

fails with: -

losetup: /tmp/tmp.bHz11oY851: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
ERROR: File /dev/loop0p1 is not a block device
losetup: /tmp/tmp.bHz11oY851: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
ERROR: File /dev/loop1p1 is not a block device
losetup: /tmp/tmp.bHz11oY851: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
ERROR: File /dev/loop9p1 is not a block device
losetup: /tmp/tmp.bHz11oY851: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
ERROR: File /dev/loop10p1 is not a block device
losetup: /tmp/tmp.bHz11oY851: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
ERROR: File /dev/loop11p1 is not a block device
ERROR: File /dev/loop86p1 is not a block device
ERROR: Could not calculate the required disk size
INFO: Creating raw disk with size 126M
/root/go/src/github.com/kata-containers/kata-containers/tools/osbuilder/image-builder/image_builder.sh: line 362: qemu-img: command not found

The solution is kinda in the error - we're missing qemu-img which is easily installed: -

apt-get update && apt-get install -y qemu-utils

Hit:1 https://download.docker.com/linux/ubuntu focal InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu focal InRelease
Get:3 http://us.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Get:5 http://us.archive.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Fetched 328 kB in 1s (273 kB/s)   
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-5.4.0-72 linux-headers-5.4.0-72-generic linux-image-5.4.0-72-generic linux-modules-5.4.0-72-generic linux-modules-extra-5.4.0-72-generic
Use 'apt autoremove' to remove them.
The following additional packages will be installed:
  libiscsi7 qemu-block-extra sharutils
Suggested packages:
  debootstrap sharutils-doc bsd-mailx | mailx
The following NEW packages will be installed:
  libiscsi7 qemu-block-extra qemu-utils sharutils
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,246 kB of archives.
After this operation, 7,247 kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu focal/main amd64 libiscsi7 amd64 1.18.0-2 [63.9 kB]
Get:2 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 qemu-block-extra amd64 1:4.2-3ubuntu6.17 [54.4 kB]
Get:3 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 qemu-utils amd64 1:4.2-3ubuntu6.17 [973 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu focal/main amd64 sharutils amd64 1:4.15.2-4build1 [155 kB]
Fetched 1,246 kB in 1s (1,273 kB/s)
Selecting previously unselected package libiscsi7:amd64.
(Reading database ... 157815 files and directories currently installed.)
Preparing to unpack .../libiscsi7_1.18.0-2_amd64.deb ...
Unpacking libiscsi7:amd64 (1.18.0-2) ...
Selecting previously unselected package qemu-block-extra:amd64.
Preparing to unpack .../qemu-block-extra_1%3a4.2-3ubuntu6.17_amd64.deb ...
Unpacking qemu-block-extra:amd64 (1:4.2-3ubuntu6.17) ...
Selecting previously unselected package qemu-utils.
Preparing to unpack .../qemu-utils_1%3a4.2-3ubuntu6.17_amd64.deb ...
Unpacking qemu-utils (1:4.2-3ubuntu6.17) ...
Selecting previously unselected package sharutils.
Preparing to unpack .../sharutils_1%3a4.15.2-4build1_amd64.deb ...
Unpacking sharutils (1:4.15.2-4build1) ...
Setting up sharutils (1:4.15.2-4build1) ...
Setting up libiscsi7:amd64 (1.18.0-2) ...
Setting up qemu-block-extra:amd64 (1:4.2-3ubuntu6.17) ...
Setting up qemu-utils (1:4.2-3ubuntu6.17) ...
Processing triggers for libc-bin (2.31-0ubuntu9.2) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for install-info (6.7.0.dfsg.2-5) ...

and validated: -

which qemu-img


Actually, the Kata documentation does cover this: -

If you do not wish to build under Docker, remove the USE_DOCKER variable in the previous command and ensure the qemu-img command is available on your system.

Thursday 19 August 2021

skopeo - policy says "No"

I'm playing with skopeo on Ubuntu 20.04, having simply copied the binary from one box to another ...

Having validated the binary: -

which skopeo


ls -al `which skopeo`

-rwxr-xr-x 1 root root 26859648 Aug 19 09:44 /usr/bin/skopeo

skopeo --version

skopeo version 1.3.0

I tried and, alas, failed to pull an image using skopeo copy ...

skopeo copy docker://registry.fedoraproject.org/fedora:latest dir:/tmp/fedora.image

FATA[0000] Error loading trust policy: open /etc/containers/policy.json: no such file or directory

I checked for the missing file: -

find / -name "policy.json" 2>/dev/null

but to no avail.

Given that I knew that this worked on another Ubuntu 20.04 box, I checked for the file over there: -

find / -name "policy.json" 2>/dev/null


and grabbed a look at it: -

cat /etc/containers/policy.json

    "default": [
            "type": "insecureAcceptAnything"
                    "": [{"type":"insecureAcceptAnything"}]

Knowing what it should look like, I created a duplicate on the "new" Ubuntu box: -

mkdir -p /etc/containers

cat <<EOF | tee /etc/containers/policy.json
    "default": [
            "type": "insecureAcceptAnything"
                    "": [{"type":"insecureAcceptAnything"}]

and verified it: -

find / -name "policy.json" 2>/dev/null


cat /etc/containers/policy.json

    "default": [
            "type": "insecureAcceptAnything"
                    "": [{"type":"insecureAcceptAnything"}]

so then just re-ran the skopeo copy command: -

skopeo copy docker://registry.fedoraproject.org/fedora:latest dir:/tmp/fedora.image

Getting image source signatures
Copying blob ecfb9899f4ce done
Copying config 37e5619f4a done
Writing manifest to image destination
Storing signatures

Sweet !

I suspect that things didn't originally work due to the way that I "installed" skopeo on this box, via scp rather than a "proper" installation or build.

Nice !

Wednesday 18 August 2021

More K8s insights using kubectl

From my IBM colleague: -

Get the name of the all the nodes’ name, os image, os architecture, pod cidrs, internal and external ip address

kubectl get nodes -o custom-columns='NODE-NAME:.metadata.name,OS-IMAGE:.status.nodeInfo.osImage,OS-ARCH:.status.nodeInfo.architecture,POD-CIDRs:.spec.podCIDRs[*],INTERNAL-IP:.status.addresses[?(@.type=="InternalIP")].address,EXTERNAL-IP:.status.addresses[?(@.type=="ExternalIP")].address'

which, for me, shows: -

NODE-NAME               OS-IMAGE             OS-ARCH   POD-CIDRs       INTERNAL-IP    EXTERNAL-IP
sideling1.example.com   Ubuntu 20.04.2 LTS   amd64   <none>
sideling2.example.com   Ubuntu 20.04.2 LTS   amd64    <none>

Tuesday 17 August 2021

And there's more - kubectl and jsonpath FTW

Again, from my ever-generous colleague: -

Get all the pods that are using specific configmap. Change the configmap name according to your requirement in @.spec.volumes[*].configMap.name=="test-config"

which worked for me using the coredns configMap. 

First I queried for configMaps on my cluster: -

kubectl get configmaps -A

NAMESPACE         NAME                                 DATA   AGE
default           kube-root-ca.crt                     1      57d
kube-node-lease   kube-root-ca.crt                     1      57d
kube-public       cluster-info                         1      57d
kube-public       kube-root-ca.crt                     1      57d
kube-system       calico-config                        4      57d
kube-system       coredns                              1      57d
kube-system       extension-apiserver-authentication   6      57d
kube-system       kube-proxy                           2      57d
kube-system       kube-root-ca.crt                     1      57d
kube-system       kubeadm-config                       2      57d
kube-system       kubelet-config-1.21                  1      57d

and then for Pods using that particular configMap: -

kubectl get pods --all-namespaces -o jsonpath='{range $.items[?(@.spec.volumes[*].configMap.name=="coredns")]}{.metadata.name}{"\t"}{.spec.volumes[*].configMap.name}{"\n"}{end}'

coredns-558bd4d5db-dmnnc coredns
coredns-558bd4d5db-t8xnm coredns

Note that I'm including --all-namespaces to catch all Pods, especially as I'm not running much in the default namespace.

Two bits of additional insight from the K8s documentation: -

Monday 16 August 2021

And another one - the Kubernetes tips keep on coming - and I keep on sharing 'em

 This one is rather useful, and again continues the use of jsonpath

Get the name of the all the nodes and their corresponding InternalIP address.

kubectl get nodes -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.addresses[?(@.type=="InternalIP")].address}{"\n"}{end}'


Sunday 15 August 2021

More Kubernetes goodness ....

My uber-smart colleague has continued to post really rather useful kubectl tips and tricks, including this most recent one: -

Get all the pods that are on specific node. Change the node name accordingly

kubectl get pods -o jsonpath='{range $.items[?(@.spec.nodeName=="kubenode01")]}{.metadata.name}{"\t"}{.spec.nodeName}{"\n"}{end}'

Initially, this didn't appear to work for me - in that it didn't return anything ... that, of course, was a PEBCAK

Initially, I thought that was because my node names included the host AND domain names

Of course, it wasn't that - it was just that I didn't actually have any pods deployed to the default namespace.

Once I amended the command to include ALL namespaces, all was well: -

kubectl get pods --all-namespaces -o jsonpath='{range $.items[?(@.spec.nodeName=="sideling1.example.com")]}{.metadata.name}{"\t"}{.spec.nodeName}{"\n"}{end}'

calico-kube-controllers-cc8959d7f-9qhh4 sideling1.example.com
calico-node-kwj42 sideling1.example.com
coredns-558bd4d5db-dmnnc sideling1.example.com
coredns-558bd4d5db-t8xnm sideling1.example.com
etcd-sideling1.example.com sideling1.example.com
kube-apiserver-sideling1.example.com sideling1.example.com
kube-controller-manager-sideling1.example.com sideling1.example.com
kube-proxy-kz2cm sideling1.example.com
kube-scheduler-sideling1.example.com sideling1.example.com

kubectl get pods --all-namespaces -o jsonpath='{range $.items[?(@.spec.nodeName=="sideling2.example.com")]}{.metadata.name}{"\t"}{.spec.nodeName}{"\n"}{end}'

calico-node-jd867 sideling2.example.com
kube-proxy-bc897 sideling2.example.com

Thursday 12 August 2021

Tinkering with Kubernetes via kubectl - some pearls of wisdom ( from other way smarter people )

 I filched these two gems from a much smarter person and am re-posting them here ...

The first relates to Pod labels which, to be honest, I've not paid too much attention.

The original context was to use kubectl to retrieve the IP address of Pods with a specific Label, using nginx as an example.

I've built upon these using Calico Node as an example ...

So I've got two Calico Node pods running inside my cluster: -

kube-system   calico-node-jd867                                1/1     Running   3          13d
kube-system   calico-node-kwj42                                1/1     Running   0          13d

If I describe each of those Pods, I can retrieve their Labels ...

kubectl describe pod calico-node-jd867 --namespace kube-system

Labels:               controller-revision-hash=74c54477d6

kubectl describe pod calico-node-kwj42 --namespace kube-system

Labels:               controller-revision-hash=74c54477d6

Armed with the Labels, I can query just for Pods using one of those Labels e.g.

kubectl get pods --all-namespaces --selector k8s-app=calico-node

kube-system   calico-node-jd867   1/1     Running   3          13d
kube-system   calico-node-kwj42   1/1     Running   0          13d

Building upon that, I can then get, from each Pod, its respective IP address: -

kubectl get pods --all-namespaces --selector k8s-app=calico-node --output jsonpath='{range .items[*]}{.status.podIP}{"\n"}{end}'

Pivoting away from Pods and Labels, we can similarly use kubectl and some JSON wrangling to retrieve the Taints from each Node in the cluster: -

kubectl get nodes -o jsonpath='{range $.items[*]} {.metadata.name} {.spec.taints[*].effect}{"\n"}{end}'

 sideling1.example.com NoSchedule

which is rather shiny !

Again, definitely NIH, but reposting 'cos it's awesome

Thursday 5 August 2021

TIL: serialisation and deserialisation in Rust ...

Whilst digging through the source of the Kata Containers project, specifically the kata-agent and kata-agent-ctl code, both of which are written in Rust, I kept coming across references to serde ...

e.g. from utils.rs 

pub fn spec_file_to_string(spec_file: String) -> Result<String> {
    let oci_spec = ociSpec::load(&spec_file).map_err(|e| anyhow!(e))?;
    serde_json::to_string(&oci_spec).map_err(|e| anyhow!(e))

Having first assumed that this was some shorthand, I dug further and found this: -

Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.

Serialization framework for Rust

Having used serialisation and deserialisation in Java back in the day, this made sense....

Serialization is a mechanism of converting the state of an object into a byte stream. Deserialization is the reverse process where the byte stream is used to recreate the actual Java object in memory. This mechanism is used to persist the object.

Serialization and Deserialization in Java with Example

So now I know ....

Wednesday 4 August 2021

Tinkering with Rust - an underscore

Whilst tinkering with the Kata Containers kata-agent component, I was trying to work out what the underscore meant in this line of code: -

let _ = spec.save(config_path.to_str().unwrap());

Thankfully, this GitHub issue: -

Documet let _ = ... behavior saliently, or even warn about it #40096

led me to this section of the Rust language book: -

Ignoring Values in a Pattern

You’ve seen that it’s sometimes useful to ignore values in a pattern, such as in the last arm of a match, to get a catchall that doesn’t actually do anything but does account for all remaining possible values. There are a few ways to ignore entire values or parts of values in a pattern: using the _ pattern (which you’ve seen), using the _ pattern within another pattern, using a name that starts with an underscore, or using .. to ignore remaining parts of a value. Let’s explore how and why to use each of these patterns.

and: -

We’ve used the underscore (_) as a wildcard pattern that will match any value but not bind to the value. Although the underscore _ pattern is especially useful as the last arm in a match expression, we can use it in any pattern, including function parameters, as shown in Listing 18-17.

Ignoring an Entire Value with _

More on macOS SMB sharing

As a follow-up to an earlier post: - macOS to macOS File Sharing - Don't work, try The IT Crowd I hit this problem again and referred ba...