dockerhub registery: x509: certificate signed by unknown authority

Question

I've spend hours looking to solve this issue, however I'm unable to find any topics related to this issue, since all I find is custom registeries. When running any of the docker commands that connect to docker hub, either through https://registry-1.docker.io/v2/ or https://index.docker.io/v1 , all requests end up in "x509: certificate signed by unknown authority". However using curl to run query the same endpoints seem to function just fine.

I've reinstalled docker completely, purging all configuration files, however it does not seem to make a difference.

Anything I'm missing?

docker info :

Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 17.05.0-ce
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins: 
 Volume: local
 Network: bridge host macvlan null overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 9048e5e50717ea4497b757314bad98ea3763c145
runc version: 9c2d8d184e5da67c95d601382adf14862e4f2228
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.9.35-1-lts
Operating System: Arch Linux
OSType: linux
Architecture: x86_64
CPUs: 8
Total Memory: 15.34GiB
ID: 5Q4D:TLJF:3I3U:O522:VQMK:24BU:H5ND:UPOU:MWYS:WGTB:XFXR:BQES
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Ena

Using docker :

[user@hostname]$ docker search ubunut
Error response from daemon: Get https://index.docker.io/v1/search?q=ubunut&n=25: x509: certificate signed by unknown authority

Using curl :

[user@hostname]$ curl -v  https://index.docker.io/v1/search?q=ubunut&n=25
[1] 2152
[user@hostname]$ *   Trying 34.200.194.233...
* TCP_NODELAY set
* Connected to index.docker.io (34.200.194.233) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server did not agree to a protocol
* Server certificate:
*  subject: OU=GT98568428; OU=See www.rapidssl.com/resources/cps (c)15; OU=Domain Control Validated - RapidSSL(R); CN=*.docker.io
*  start date: Mar 19 17:34:32 2015 GMT
*  expire date: Apr 21 01:51:52 2018 GMT
*  subjectAltName: host "index.docker.io" matched cert's "*.docker.io"
*  issuer: C=US; O=GeoTrust Inc.; CN=RapidSSL SHA256 CA - G3
*  SSL certificate verify ok.
> GET /v1/search?q=ubunut HTTP/1.1
> Host: index.docker.io
> User-Agent: curl/7.54.1
> Accept: */*
> 
< HTTP/1.1 200 OK
< Server: nginx/1.6.2
< Date: Wed, 05 Jul 2017 12:10:22 GMT
< Content-Type: application/json
< Transfer-Encoding: chunked
< Vary: Cookie
< X-Frame-Options: SAMEORIGIN
< Strict-Transport-Security: max-age=31536000
< 
{"num_pages": 1, "num_results": 21, "results": [{"is_automated": true, "name": "han4wluc/try-docker-ubunut-node", "is_trusted": true, ... *truncated*

Answer 1

I solved the problem as follows:

1. I removed the file /etc/ssl/cert/ca-certificates.crt .
2. I ran the command sudo pacman -S ca-certificates-utils .
3. I restarted docker with the systemctl restart docker command.

I got this hint from this link:

https://unix.stackexchange.com/questions/339613/arch-linux-ca-certificates-crt-not-found/396169#396169