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Known issues and workarounds

This chapter describes a list of known issues and how to fix them in the CERN cloud.

CC7 machine clock on localtime

Issue

As part of an internal audit on the cloud infrastructure service, we have discovered an issue on some of the instances that have been wrongly configured.

All linux images are configured to rely on UTC for the hypervisor clock, and all those instances were booted from an image that had a bug configuring the clock that set it up to localtime.

If those machines get recreated by one of our campaigns or directly by the end user, they will lose network connectivity through kerberos.

Fix

To address this, we encourage you to follow the next steps to fix the clock:

  • log into the VM
  • adjust the file /etc/adjtime and replace LOCAL by UTC
  • reboot the VM

CC7 instance configured to static network

Issue

As part of the preparations for the recreation campaign, we have identified an inconsistency in the way that some CC7 images configure the network. Some of them rely on the metadata service while the newer ones rely on DHCP.

Fix

In order to find a common and consistent way of configuring the network and following the recommendation from the Linux Team, we would like you to review the network configuration on your VM, you can just run the following commands on your CC7 VM:

# disable cloud-init managing network
cat >> /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg << EOF
network: {config: disabled}
EOF

# initscripts don't like this file to be missing.
cat > /etc/sysconfig/network << EOF
NETWORKING=yes
NOZEROCONF=yes
EOF

# simple eth0 config, again not hard-coded to the build hardware
cat > /etc/sysconfig/network-scripts/ifcfg-eth0 << EOF
NAME="eth0"
DEVICE="eth0"
ONBOOT="yes"
NETBOOT="yes"
IPV6INIT="yes"
BOOTPROTO="dhcp"
TYPE="Ethernet"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
DHCPV6_DUID="llt"
USERCTL="yes"
PEERDNS="yes"
PERSISTENT_DHCLIENT="1"
EOF

Last update: July 8, 2022