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The system will enter the rescue mode after the ECS instance is upgraded from Systemd to systemd-219-71.el7

Last Updated: Jul 06, 2020

Problem description

Single CPU specification and the system is CentOS 7 or Red Hat 7 series the ECS instance after you upgrade Systemd to systemd-219-71.el7 after you upgrade the instance, the instance enters the maintenance mode after you restart the instance. The following information is displayed:

Give root password for maintenance
(or press Control-D to continue):

This can cause exceptions to system network services and general application services.

Causes

On CentOS 7 or RedHat 7 Series systems, the Systemd package is upgraded to systemd-219-71.el7 bugs in the old package are triggered by the version conflict, causing the ECS instance to enter rescue mode after it is restarted. ECS instances that meet the following requirements may encounter this problem:

  • The ECS instance uses a CentOS 7 or Red Hat 7 Series version. .
  • Upgrade Systemd to systemd-219-71.el7 version, and restart. The following table lists the scenarios that may trigger Systemd upgrade:
    • Upgrade Systemd. For example, through yum update command to upgrade all software packages or the Systemd package.
    • Use security center to fix vulnerabilities. When fixing the vulnerability, security center may update the Systemd software package.
  • ECS instances use a single CPU. The single-CPU instance types are as follows:
    • ecs.s6-c1m1.small  
    • ecs.s6-c1m2.small  
    • ecs.s6-c1m4.small
    • ecs.xn4.small  
    • ecs.n1.small
    • ecs.n4.small  
    • ecs.e4.small
    • ecs.e3.small
    • ecs.mn4.small  
    • ecs.n1.tiny  
    • ecs.n2.small  
    • ecs.t5-lc2m1.nano  
    • ecs.t5-lc1m1.small  
    • ecs.t5-lc1m2.small  

For more information about this issue, see Red Hat official documentation.

Solutions

If your ECS instance is a single-CPU instance running CentOS 7 or Red Hat 7, select either of the following methods:

  • The Systemd program has been upgraded and the ECS instance is in the rescue mode.
    If the ECS instance has entered the rescue mode, follow these steps:
    1. Create a snapshot to back up the system disk of the ECS instance. For more information, see create a normal snapshot.
    2. Log on to the ECS instance as the root user by using Alibaba Cloud VNC. 
    3. Run the following command to generate grub parameter
      dracut --force --regenerate-all
    4. Restart the ECS instance.
  • The ECS instance is in the normal state and you are about to upgrade your Systemd system.
    In doing anything that may trigger Systemd upgrade operation or back up the system snapshot before installing and updating application software.

Application scope

  • Elastic Compute Service (ECS)