Updating repository information warning failed to read mirror file
This backup may help to restore or recreate the old settings. Any package installation operation must be run with superuser privileges, so either log in as There might be services that are offered by the system which are associated with packages that will be included in the upgrade.
If this is the case, please note that, during the upgrade, these services will be stopped while their associated packages are being replaced and configured.
For emergency recovery we generally recommend using the of the stretch Debian Installer.If that fails, you will need an alternative way to boot your system so you can access and repair it.One option is to use a special rescue image or a Linux live CD.After booting from that, you should be able to mount your root file system and in the initrds it generates.If for example the initrd is unable to mount your root file system, you will be dropped into this debug shell which has basic commands available to help trace the problem and possibly fix it.