The virtual machine fails to start. What should I do?

Virtual machine startup failures can manifest in several ways. Identify the applicable symptom and cause, then follow the corresponding solution to resolve the issue.

Symptom

Virtual machine startup failures may present as the following four symptoms:

• Symptom 1: After entering the Linux virtual machine, the following error appears: welcome to emergency mode! After logging in, type "journalctl -x b" to view system logs, "systemctl reboot"to reboot, "systemctl default"to try again to boot into default mode. Give root password for maintenance.
• Symptom 2: The virtual machine fails to start with the error: stderr:exec of\"/usr/local/zstack/dnsmasq\"failed:No such file or directory\n","location":".
• Symptom 3: The virtual machine console displays a black screen.

Cause 1

Symptom 1 may result from either of the following causes:

• Automatic Data Disk mounting at startup fails.
• An unexpected host power outage causes file system corruption.

Solution

• If automatic Data Disk mounting at startup fails, follow these steps:

  1. Log in to the virtual machine and remove or comment out the Data Disk mount command in the /etc/fstab configuration file.

  2. Edit the /etc/rc.d/rc.local configuration file to configure automatic Data Disk mounting at startup using the disk UUID.

• If file system corruption results from a host power outage, follow this step:

  Use a file system repair tool or a third-party livecd tool to boot and repair the file system.

Cause 2

Symptom 2 may occur because a host power outage caused the dnsmasq file to be lost.

Solution

1. Use the scp command to copy the /usr/local/zstack/dnsmasq file from a healthy host node to the affected host.

2. Reconnect the host.

3. Restart the virtual machine.

Cause 3

Symptom 3 may occur because an SElinux configuration file load error prevents the system from starting normally.

Solution

• Boot into single-user mode and check the SElinux configuration file for parameter errors. If errors are found, correct them and restart the virtual machine.