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Container migration from Virtuozzo 6 to Virtuozzo Hybrid Server 7.5 fails with connectivity error (arcfour)

  • Updated
Applies to:
  • Virtuozzo Hybrid Server 7.x

Symptoms

Upon trying to migrate a container from Virtuozzo 6 to Virtuozzo Hybrid Server 7.5 Update 5 and later versions, the error appears:

29.08.2023-20.08.16: ssh exited with code 255
29.08.2023-20.08.16: ssh wait daemon exited with code 1
29.08.2023-20.08.16: vzsock_open() return 1
29.08.2023-20.08.16: Can not create connection to $DESTINATION_VHS7

Cause

Virtuozzo 6 migration is using "arcfour" as a default cipher for ssh connection opened during the migration, which is outdated and does not present by default in the configuration for in Virtuozzo Hybrid Server 7.5 Update 5 and later versions when it is a fresh installation.

Resolution

Modify configuration files on Virtuozzo Hybrid Server 7.5 server to add 'arcfour' cipher for migration purposes. Once the migration is over it is recommended to remove the outdated 'arcfour' cipher.

1. Add the 'arcfour' cipher on Virtuozzo Hybrid Server 7.5:

# echo "`sshd -T | grep ciphers`,arcfour"

Real-life example:

$ echo "`sshd -T | grep ciphers`,arcfour"
ciphers chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc,arcfour

2. Reload sshd to apply changes.

# systemctl restart sshd

3. Re-try container migration.

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