i tried to update the docker container using apt-uppdate but faced certificate issue i tried to install the certificate but gnupg not available in the docker container i tried to install gnupg but due to certificate issue failed proxy also added in the docker container
apt update
Get:1 http://security.ubuntu.com/ubuntu jammy-security InRelease [110 kB]
Get:2 http://archive.ubuntu.com/ubuntu jammy InRelease [270 kB]
Err:1 http://security.ubuntu.com/ubuntu jammy-security InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Get:3 http://archive.ubuntu.com/ubuntu jammy-updates InRelease [114 kB]
Err:2 http://archive.ubuntu.com/ubuntu jammy InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Err:3 http://archive.ubuntu.com/ubuntu jammy-updates InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Get:4 http://archive.ubuntu.com/ubuntu jammy-backports InRelease [99.8 kB]
Err:4 http://archive.ubuntu.com/ubuntu jammy-backports InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Reading package lists... Done
W: http://security.ubuntu.com/ubuntu/dists/jammy-security/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://security.ubuntu.com/ubuntu/dists/jammy-security/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://security.ubuntu.com/ubuntu jammy-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://security.ubuntu.com/ubuntu jammy-security InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://archive.ubuntu.com/ubuntu/dists/jammy/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-backports/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-backports/InRelease: The key(s) in the keyring
/etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Problem executing scripts APT::Update::Post-Invoke 'rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true'
E: Sub-process returned an error code
root@f63068899287:/# apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 871920D1991BC93C
E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation
root@f63068899287:/#
root@f63068899287:/# apt install gnupg
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package gnupg is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'gnupg' has no installation candidate