Not sure why, but the EPEL repo is installed, but disabled by default. You can enable it permanently by changing the setting "enabled=1" in the [epel] stanza of /etc/yum.repos.d/epel.repo
Or you can leave it disabled and still install byobu:
sudo yum install --enablerepo=epel byobu
You can have a look at what packages are available in the epel repo with:
sudo yum list --disablerepo=\* --enablerepo=epel
To install specific package from specific repo you can use
yum install --enablerepo=name-of-repo name-of-package
Say there can be conflict between version, consider example of installing mariadb 5.5.66, in my case I got 2 repo mariadb-5 and mariadb-10, suppose if I wish to install from mariadb-5 repo then I use
yum install --disablerepo=mariadb-10 --enablerepo=mariadb-5 MariaDB-server MariaDB-client
To enable enable specific repo, you can use
yum-config-manager --enable name-of-repo
Here is example on Centos 7.7
[root@localhost server-setup]# cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)
[root@localhost server-setup]# yum repolist
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirrors.piconets.webwerks.in
* epel: mirror.poliwangi.ac.id
* extras: mirrors.piconets.webwerks.in
* remi-safe: mirror.innosol.asia
* updates: mirrors.piconets.webwerks.in
repo id repo name status
CodeIT/x86_64 CodeIT repo 369
base/7/x86_64 CentOS-7 - Base 10,097
epel/x86_64 Extra Packages for Enterprise Linux 7 - x86_64 13,453
extras/7/x86_64 CentOS-7 - Extras 305
ius/x86_64 IUS for Enterprise Linux 7 - x86_64 641
mariadb-10 MariaDB 94
mariadb-5 MariaDB 39
remi-safe Safe Remi's RPM repository for Enterprise Linux 7 - x86_64 3,621
updates/7/x86_64 CentOS-7 - Updates 711
repolist: 29,330
To Disable
[root@localhost server-setup]# yum-config-manager --disable mariadb-5
After Disabling
[root@localhost server-setup]# yum repolist
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirrors.piconets.webwerks.in
* epel: mirror.poliwangi.ac.id
* extras: mirrors.piconets.webwerks.in
* remi-safe: mirror.innosol.asia
* updates: mirrors.piconets.webwerks.in
repo id repo name status
CodeIT/x86_64 CodeIT repo 369
base/7/x86_64 CentOS-7 - Base 10,097
epel/x86_64 Extra Packages for Enterprise Linux 7 - x86_64 13,453
extras/7/x86_64 CentOS-7 - Extras 305
ius/x86_64 IUS for Enterprise Linux 7 - x86_64 641
mariadb-10 MariaDB 94
remi-safe Safe Remi's RPM repository for Enterprise Linux 7 - x86_64 3,621
updates/7/x86_64 CentOS-7 - Updates 711
repolist: 29,291
What it actually does ???
I got MariaDB.repo file at /etc/yum.repos.d/, when you use --enable <repo-name> or --disable <repo-name>, it will change the value of enabled = to 0 or 1, based on this, yum repolist will show you repositories.
[root@localhost server-setup]# cat /etc/yum.repos.d/MariaDB.repo
[mariadb-10]
name = MariaDB
baseurl = http://yum.mariadb.org/10.4.10/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1
[mariadb-5]
name = MariaDB
baseurl = http://yum.mariadb.org/5.5.66/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1
enabled = 1
Best Answer
You just needed to update ca-certificates package. Before that just disable all repos with https that are failing. That's why solution with commenting mirrorlist or using http instead https would work also.
For example if you need to disable only epel repo:
This will also help wget, curl, and anything else that uses SSL certificates.