There is also the option of an error “in between”, also known as PEBCAC:
“Problem exists between Console and Chair”, or simple human error, typos, not reading the Fine manual (RTFM)…
A defective LAN cable has also been guilty in countless migrations!
Note:
This is not intended as a sidekick to the excellent work of @Stephdl or @NLS in debugging NS8 migration!
My 2 cents
Andy
PEBCAC is always a factor, speaking from my 40 year computing experience of which 25+ are professional, although I don’t love it if someone rubs it on my face @Andy_Wismer …
To be honest I find it weird that the migration fails in a scenario as simple as mine, I suspect way more complex and fully utilized NS7 than mine, that… worked? (or just not migrated yet)
I assure you the network connection between the two VMs on the same physical machine 
works fine and the server is on a 10Gbit switch anyway if that was a factor.
I hope to be able to test tonight.
I did specifically write it’s NOT intended as a sidekick against either you or Stephan.
And I did write “excellent work”, and that’s meant that way. I am for anything that forewards NS8!
Besides which: As you’re not even using Roundcube, yet the migration barfs due to Roundcube, I can’t really blame you for this issue in any way! I see you as helping solve a bug you found, excellent work!
But if you find an offence in any of the above…
My actual intention was to remind Stephan that there are not only programmers at fault when something goes south. Often, there are “unexpected” issues in any migration.
Ever ran into a 4 hour long, City wide Blackout during. right in the middle of a migration? Longer than our UPS would support, and all due to a Squirel which jumped in the wrong hole in the Substation responsible for the City of Zurich. A few years back, on a Saturday before xMas in December! (True).
The squirel made national news - as a pieve of Grilled meat (Not anymore identifyable). And I had a fried RAID… 
And no, I’m not blaming you for training that squirel!
But as you also know from experience in IT: Sh*t happens!
Good luck for testing!
My 2 cents
Andy
No worries man.
I was not offended as much as you think. 
Anyway…
…BOOM…
Error
Synchronization failed
The following command has failed:
nethserver-ns8-migration/migration/update
Unfortunately we couldn't catch the exact error. If you want to help, please click on the button below to copy the failed command to the clipboard, paste it into the Terminal and submit command output to the developers.
and the “copy command” gives this:
echo '{"app":"nethserver-mail","action":"finish","migrationConfig":{"roundCubeVirtualHost":""}}' | /usr/bin/setsid /usr/bin/sudo /usr/libexec/nethserver/api/nethserver-ns8-migration/migration/update | jq
As last time, my services are down in NS7.
I send you the logs you asked in PM…
I got nothing ???
we need logs of NS7 and NS8
Will try to reproduce today
well the mail migration is broken, I need to investigate why, other module like LDAP, mattermost works well
I tried to keep only the mail module and the migration failed
ok I found the bug, I have a fix to propose, to be short if you want to test the migration
yum remove nethserver-roundcubemail-next
it is the root cause, I have a fix to patch
Is inaccessible web interface for mail and nextcloud caused by or not associated with round cube
to test the migration when nethserver-roundcubemail-next is installed install this rpm
yum install http://packages.nethserver.org/nethserver/7.9.2009/autobuild/x86_64/Packages/nethserver-ns8-migration-1.0.7-1.4.pr58.ga8916a3.ns7.x86_64.rpm -y
…so should I make any new tests or wait for you first?
I did the test for you. For what I see the fact that nethserver-roundcubemail-next is installed was the root cause
With the rpm above it should work
OK will test tonight.
No @stephdl , still failed…
Same place.
echo '{"app":"nethserver-mail","action":"finish","migrationConfig":{"roundCubeVirtualHost":""}}' | /usr/bin/setsid /usr/bin/sudo /usr/libexec/nethserver/api/nethserver-ns8-migration/migration/update | jq
Will try to get logs from both systems…
rpm -qa | grep migration
rpm -qa | grep nethserver
I succeed to migrate
pop3 connector
webtop
mail
opeldap
to a ns8 on rocky9 with that list of rpm
[root@NS2 ~]# rpm -qa | grep nethserver
nethserver-cockpit-1.10.12-1.ns7.noarch
nethserver-firewall-base-3.19.3-1.ns7.noarch
nethserver-hosts-1.2.2-1.ns7.noarch
nethserver-lsm-1.2.4-1.ns7.noarch
nethserver-directory-3.4.3-1.ns7.noarch
nethserver-antivirus-1.6.1-1.ns7.noarch
nethserver-duc-1.7.0-1.ns7.noarch
nethserver-httpd-admin-service-2.7.1-1.ns7.noarch
nethserver-postgresql-1.1.0-1.ns7.noarch
nethserver-phonehome-1.4.0-1.ns7.noarch
nethserver-roundcubemail-next-1.5.7-1.ns7.noarch
nethserver-base-3.9.1-1.ns7.noarch
nethserver-lib-2.2.11-1.ns7.noarch
nethserver-ntp-1.1.3-1.ns7.noarch
nethserver-nethforge-release-7-3.ns7.noarch
nethserver-conference-0.1.0-1.ns7.noarch
nethserver-rh-php73-php-fpm-1.0.0-1.ns7.noarch
nethserver-release-7-19.ns7.noarch
nethserver-rh-mariadb105-1.0.0-1.ns7.noarch
nethserver-subscription-ui-3.6.10-1.ns7.noarch
nethserver-yum-1.4.1-1.ns7.noarch
nethserver-php-1.3.0-1.ns7.noarch
nethserver-dnsmasq-1.7.2-1.ns7.noarch
nethserver-smartd-1.1.0-1.ns7.noarch
nethserver-openssh-1.8.0-1.ns7.noarch
nethserver-stephdl-1.1.9-1.ns7.sdl.noarch
nethserver-lang-cockpit-1.4.6-27.ns7.noarch
nethserver-subscription-inventory-3.6.10-1.ns7.x86_64
nethserver-backup-config-2.5.3-1.ns7.noarch
nethserver-sssd-1.7.1-1.ns7.noarch
nethserver-httpd-3.12.3-1.ns7.noarch
nethserver-mail-filter-2.32.2-1.ns7.noarch
nethserver-mail-getmail-2.32.2-1.ns7.noarch
nethserver-collectd-3.1.1-1.ns7.noarch
nethserver-diagtools-1.0.4-1.ns7.noarch
nethserver-unbound-1.1.1-1.ns7.noarch
nethserver-mail-common-2.32.2-1.ns7.noarch
nethserver-webtop5-1.8.17-1.ns7.noarch
nethserver-ns8-migration-1.0.7-1.4.pr58.ga8916a3.ns7.x86_64
nethserver-subscription-3.6.10-1.ns7.noarch
nethserver-netdata-2.0.4-1.ns7.noarch
nethserver-mail-smarthost-2.32.2-1.ns7.noarch
nethserver-backup-data-1.7.6-1.ns7.noarch
nethserver-mail-server-2.32.2-1.ns7.noarch
nethserver-cockpit-lib-1.10.12-1.ns7.noarch
nethserver-mail-imapsync-2.32.2-1.ns7.noarch
can you double check your difference, did you upgrade migration ?
Those greps are for NS7 or NS8?
I did update migration first with 1.0.7-1.4.pr58.ga8916a3, yes.
My NS7 is reverted from backup, so migration is now back to the “stock” version.
But for the packages:
nethserver-postgresql94-1.0.0-1.ns7.noarch
nethserver-phpldapadmin-1.0.4-1.ns7.noarch
nethserver-pulledpork-2.1.7-1.ns7.noarch
nethserver-mail-p3scan-2.32.2-1.ns7.noarch
nethserver-subscription-3.6.10-1.ns7.noarch
nethserver-firewall-base-3.19.3-1.ns7.noarch
nethserver-httpd-virtualhosts-3.12.3-1.ns7.noarch
nethserver-postgresql-1.1.0-1.ns7.noarch
nethserver-rh-php56-php-fpm-1.0.0-1.ns7.noarch
nethserver-httpd-admin-2.7.1-1.ns7.noarch
nethserver-mail-server-2.32.2-1.ns7.noarch
nethserver-rh-php72-php-fpm-1.1.1-1.ns7.noarch
nethserver-ns8-migration-1.0.7-1.ns7.x86_64 (remember back from backup)
nethserver-blacklist-1.3.0-1.ns7.noarch
nethserver-backup-config-2.5.3-1.ns7.noarch
nethserver-yum-1.4.1-1.ns7.noarch
nethserver-webtop5-1.8.17-1.ns7.noarch
nethserver-mattermost-1.8.22-1.ns7.x86_64
nethserver-cgp-2.4.1-1.ns7.noarch
nethserver-duc-1.7.0-1.ns7.noarch
nethserver-diagtools-1.0.4-1.ns7.noarch
nethserver-mail-smarthost-2.32.2-1.ns7.noarch
nethserver-mail-imapsync-2.32.2-1.ns7.noarch
nethserver-cockpit-lib-1.10.12-1.ns7.noarch
nethserver-unbound-1.1.1-1.ns7.noarch
nethserver-sssd-1.7.1-1.ns7.noarch
nethserver-httpd-3.12.3-1.ns7.noarch
nethserver-phonehome-1.4.0-1.ns7.noarch
nethserver-mysql-1.1.5-1.ns7.noarch
nethserver-rh-php73-php-fpm-1.0.0-1.ns7.noarch
nethserver-openssh-1.8.0-1.ns7.noarch
nethserver-release-7-19.ns7.noarch
nethserver-evebox-1.4.2-1.ns7.noarch
nethserver-ejabberd-1.8.5-1.ns7.noarch
nethserver-postgresql12-1.0.0-1.ns7.noarch
nethserver-conference-0.1.0-1.ns7.noarch
nethserver-restore-data-2.0.7-1.ns7.noarch
nethserver-stephdl-1.1.9-1.ns7.sdl.noarch
nethserver-lsm-1.2.4-1.ns7.noarch
nethserver-ntp-1.1.3-1.ns7.noarch
nethserver-mail-common-2.32.2-1.ns7.noarch
nethserver-mail-getmail-2.32.2-1.ns7.noarch
nethserver-subscription-inventory-3.6.10-1.ns7.x86_64
nethserver-netdata-2.0.4-1.ns7.noarch
nethserver-fail2ban-1.7.3-1.ns7.noarch
nethserver-lib-2.2.11-1.ns7.noarch
nethserver-lang-en-1.4.6-27.ns7.noarch
nethserver-lang-cockpit-1.4.6-27.ns7.noarch
nethserver-php-1.3.0-1.ns7.noarch
nethserver-unixODBC-1.0.0-1.ns7.noarch
nethserver-vsftpd-1.1.1-1.ns7.noarch
nethserver-cockpit-1.10.12-1.ns7.noarch
nethserver-httpd-admin-service-2.7.1-1.ns7.noarch
nethserver-mail-filter-2.32.2-1.ns7.noarch
nethserver-nethforge-release-7-3.ns7.noarch
nethserver-antivirus-1.6.1-1.ns7.noarch
nethserver-dante-1.0.6-1.ns7.noarch
nethserver-backup-data-1.7.6-1.ns7.noarch
nethserver-dnsmasq-1.7.2-1.ns7.noarch
nethserver-dc-1.9.2-1.ns7.x86_64
nethserver-hosts-1.2.2-1.ns7.noarch
nethserver-base-3.9.1-1.ns7.noarch
nethserver-collectd-3.1.1-1.ns7.noarch
nethserver-smartd-1.1.0-1.ns7.noarch
nethserver-subscription-ui-3.6.10-1.ns7.noarch
nethserver-suricata-2.6.2-1.ns7.noarch
nethserver-firewall-base-ui-3.19.3-1.ns7.noarch
nethserver-httpd-proxypass-3.12.3-1.ns7.noarch
About your question in PM, I got that log from “/var/log/ns8-migration.log” (in my NS7).
I haven’t managed to somehow move my logs to somewhere I can actually pull them from NS8.
Maybe I should first enable cockpit properly in NS8 as it can help me with that most probably.