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Misleading solution in 'hitting IP with wget'? #231

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LukaszKosc opened this issue Oct 26, 2021 · 2 comments
Open

Misleading solution in 'hitting IP with wget'? #231

LukaszKosc opened this issue Oct 26, 2021 · 2 comments

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@LukaszKosc
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Hi,

I was looking today on https://github.com/dgkanatsios/CKAD-exercises/blob/master/f.services.md - and I think I noticed an issue there:

in question:
Get service's ClusterIP, create a temp busybox pod and 'hit' that IP with wget

Second solution is given as:

IP=$(kubectl get svc nginx --template={{.spec.clusterIP}}) # get the IP (something like 10.108.93.130)
kubectl run busybox --rm --image=busybox -it --restart=Never --env="IP=$IP" -- wget -O- $IP:80 --timeout 2

It works only by coincident as we use the same environment variable 'IP' in host system and inside of pod, because if we change name of variable containing ip address - it fails:

IP=$(kubectl get svc nginx --template={{.spec.clusterIP}})
kubectl run busybox --rm --image=busybox -it --restart=Never --env="HA=$IP" -- wget -O- $HA:80 --timeout 2
If you don't see a command prompt, try pressing enter.
Error attaching, falling back to logs: unable to upgrade connection: container busybox not found in pod busybox_default
wget: bad address ':80'
pod "busybox" deleted
pod default/busybox terminated (Error)

so, either we skip --env part:

IP=$(kubectl get svc nginx --template={{.spec.clusterIP}}) # get the IP (something like 10.108.93.130)
kubectl run busybox --rm --image=busybox -it --restart=Never -- wget -O- $IP:80 --timeout 2

or we use again first solution but with --env variable:

IP=$(kubectl get svc nginx --template={{.spec.clusterIP}})
kubectl run busybox --rm --image=busybox -it --restart=Never --env=HA=$IP -- sh
If you don't see a command prompt, try pressing enter.
/ # wget -O- $HA:80
Connecting to 10.152.183.190:80 (10.152.183.190:80)
writing to stdout
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
-                    100% |***********************************************|   615  0:00:00 ETA
written to stdout
/ # exit
pod "busybox" deleted

Thank you for verification.

Regards,
Lukasz
@tharpta
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tharpta commented Dec 21, 2021

I also was having a problem with this question. The answer specifies using sh after the --. I was unable to get it to work with the sh command . I'd get this error. sh: can't open 'wget': No such file or directory

Running this worked for me: k run bboxtemp2 --image=busybox -it --restart=Never -- wget -O- epIP
where epIP is the IP address of the endpoint.

Also, since this is a temporary pod, the command should probably look like:

k run bboxtemp2 --image=busybox -it --rm --restart=Never -- wget -O- epIP

@zhongdai
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zhongdai commented Mar 5, 2022

I had a simple fix, just don't run the wget directly, but swap a new sh to run it, and you can use single quote for the command with $.

❯ kubectl run nginx --image=nginx --restart=Never --port=80 --expose
service/nginx created
pod/nginx created


❯ IP=$(kubectl get svc nginx --template={{.spec.clusterIP}})


❯ kubectl run busybox --rm --image=busybox -it --restart=Never --env="xxIP=$IP" -- sh -c 'wget -O- $xxIP:80 --timeout 2'
Connecting to 10.71.252.172:80 (10.71.252.172:80)
writing to stdout
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
-                    100% |********************************|   615  0:00:00 ETA
written to stdout
pod "busybox" deleted

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3 participants
@zhongdai @tharpta @LukaszKosc