How To Reset root Password on CentOS VM – XenServer

Basic steps are as follows.

  1. Shutdown VM
  2. From XenCenter, insert the CentOS iso into the VM’s Virtual DVD drive.
  3. Boot the CentOS VM in recovery mode.  If you need help with that check this post out.
  4. On the grub menu, select recover OS Installation.
  5. Run through the recovery and mount the VM’s disk where CentOS is installed
  6. You should now be able to drop to a prompt and chroot /sysimage
  7. Change the root password with passwd
  8. Shutdown the VM
  9. Eject the CentOS iso
  10. Boot up the VM and login with the new password

Install Ruby 2.6.1 via RVM on CentOS

Install Prerequisites

yum install -y curl gcc-c++ patch readline readline-devel zlib zlib-devel libyaml-devel libffi-devel openssl-devel make cmake bzip2 autoconf automake libtool bison libssh2-devel libicu-devel

Install RVM

curl -L get.rvm.io | bash -s stable

Setup RVM, install Ruby 2.6.1 and set to default.

source /etc/profile.d/rvm.sh 
rvm install 2.6.1
rvm use --default 2.6.1

You may need to add root or the user your using to the rvm group

sudo usermod -G rvm username

Pulled some of the info from here https://github.com/ytti/oxidized#installing-ruby-212-using-rvm

LibreNMS enable RRDCached on CentOS 7

Commands from https://docs.librenms.org/Extensions/RRDCached/

Create System Service

sudo vi /etc/systemd/system/rrdcached.service
[Unit]
Description=Data caching daemon for rrdtool
After=network.service
[Service]
Type=forking
PIDFile=/run/rrdcached.pid
ExecStart=/usr/bin/rrdcached -w 1800 -z 1800 -f 3600 -s librenms -U librenms -G librenms -B -R -j /var/tmp -l unix:/run/rrdcached.sock -t 4 -F -b /opt/librenms/rrd/
[Install]
WantedBy=default.target

Save with esc + :wq

Enable rrdcached service on boot up and start the service now

systemctl enable --now rrdcached.service

Enable RRDcached in librenms config

vi /opt/librenms/config.php

add/edit the following line. If it is commented out, uncomment it

$config['rrdcached'] = "unix:/run/rrdcached.sock";

Save with esc + :wq

Check the disk IO after a little bit to see if it went down.

Can’t restart auditd with systemctl

The following command

systemctl restart auditd

Returns the following error on CentOS

Failed to restart auditd.service: Operation refused, unit auditd.service may be requested by dependency only (it is configured to refuse manual start/stop).
See system logs and 'systemctl status auditd.service' for details.

Work around is to use service for the restart

service auditd restart

 

Repairing Fedora grub from chroot

Notes from repairing a Fedora drive.

Mount system in chroot.

If the system is a raid drive and your not able to access it refer to this post.  May just need to install the raid utilities.

For mounting the chroot environment refer to this post

Repairing grub

yum install grub2-efi-*

Install grub.  Change /sda to your drive, may need to specify the efi partition.

grub2-install /dev/sda

If your boot and efi partitions are mounted.

grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg

Reboot.