Helpful tips and tricks for RHEL

RHEL.md

RHEL

Quickies

• Single User Boot:
  • Select kernel in the grub menu
  • Press e
  • In kernel params, change ro to rw init=/sysroot/bin/sh
  • Press ctrl +x or F10

Install epel

Either:

yum install epel-release

Or

yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-[RHEL version].noarch.rpm

As an example for RHEL 7: yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

Further information can be found here.

Remove /home

Wanted to NFS mount my home directories on a local VM and had some trouble when removing /home:

# rmdir /home
rmdir: failed to remove ‘/home’: Device or resource busy

To fix:

# systemctl kill NetworkManager.service
# systemctl kill chronyd.service
# rmdir /home
# systemctl start chronyd.service
# systemctl start NetworkManager.service

For more throrough information, please look here.

TLP on RHEL 8

TLP is available from the EPEL repository. However, for RHEL 8 it doesn't appear available. Instead I had to manually install from EPEL 7:

# dnf install -y https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/t/tlp-1.1-1.el7.noarch.rpm
# dnf install -y https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/t/tlp-rdw-1.1-1.el7.noarch.rpm

SSL certificate failed verification

"SSL certificate failed verification"
Trying to register/update the system fails with "SSLCertificateVerifyFailedError"
Error message from "/var/log/up2date"

up2date_client.up2dateErrors.SSLCertificateVerifyFailedError: The SSL certificate failed verification.

This is the fix:

• /etc/sysconfig/rhn/up2date
  • serverURL=http://xmlrpc.rhn.redhat.com/XMLRPC # Removed 's' from https
  • useNoSSLForPackages=1