centos7 cobbler导入ubuntu18

Question

Centos7.4 部署cobbler导入ubuntu18镜像不成功，查看日志查不到明确的报错信息，centos6 7 ubuntu20镜像均可以导入成功。

cobbler import --path=/mnt --name=ubuntu18 --arch=x86_64

received on stderr: 
running: /usr/bin/file /var/www/cobbler/ks_mirror/ubuntu18-x86_64/dists/bionic/restricted/binary-i386/Release
received on stdout: /var/www/cobbler/ks_mirror/ubuntu18-x86_64/dists/bionic/restricted/binary-i386/Release: ASCII text

received on stderr: 
Found a candidate signature: breed=ubuntu, version=bionic
running: /usr/bin/file /var/www/cobbler/ks_mirror/ubuntu18-x86_64/dists/bionic/Release
received on stdout: /var/www/cobbler/ks_mirror/ubuntu18-x86_64/dists/bionic/Release: ASCII text

received on stderr: 
Found a matching signature: breed=ubuntu, version=bionic
Adding distros from path /var/www/cobbler/ks_mirror/ubuntu18-x86_64:
No distros imported, bailing out
!!! TASK FAILED !!!