while downloading ros2 packages i was Updating my apt repository cachessudo apt update, i get the following output,with E: The repository 'http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease' is not signed. i know that Xenial (16.04) repositories are not necessary for 22.04, i removed it from (software and updates > other software) but error was not solved so i need your help.
Hit:1 http://www-ftp.lip6.fr/pub/linux/distributions/Ubuntu/archive jammy InRelease
Hit:2 http://dl.openfoam.org/ubuntu jammy InRelease
Hit:3 http://www-ftp.lip6.fr/pub/linux/distributions/Ubuntu/archive jammy-updates InRelease
Hit:4 http://www-ftp.lip6.fr/pub/linux/distributions/Ubuntu/archive jammy-backports InRelease
Hit:5 https://download.docker.com/linux/ubuntu jammy InRelease
Get:6 http://security.ubuntu.com/ubuntu xenial-security InRelease [99.8 kB]
Hit:7 http://www-ftp.lip6.fr/pub/linux/distributions/Ubuntu/archive jammy-security InRelease
Hit:8 http://packages.ros.org/ros2/ubuntu jammy InRelease
Hit:9 http://packages.osrfoundation.org/gazebo/ubuntu-stable jammy InRelease
Get:10 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [99.8 kB]
Err:6 http://security.ubuntu.com/ubuntu xenial-security InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
Err:10 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
Reading package lists... Done
W: http://dl.openfoam.org/ubuntu/dists/jammy/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
W: https://download.docker.com/linux/ubuntu/dists/jammy/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
W: http://packages.osrfoundation.org/gazebo/ubuntu-stable/dists/jammy/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
W: GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://security.ubuntu.com/ubuntu xenial-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: GPG error: http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://us.archive.ubuntu.com/ubuntu xenial-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.
find /etc/apt -type f -exec grep xenial {}+
/etc/apt/sources.list.d/official-source-repositories.list.save:deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
/etc/apt/sources.list.d/official-source-repositories.list.save:deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
/etc/apt/sources.list.d/official-source-repositories.list.save:deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
/etc/apt/sources.list.d/official-source-repositories.list:deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
/etc/apt/sources.list.d/official-source-repositories.list:# deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
/etc/apt/sources.list.d/official-source-repositories.list:deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
find /etc/apt -type f -exec grep xenial {}+return anything?-exec'