Ubuntu, including server, 20.04 is launched several days ago. Many servers with 19.10 or earlier system are planed to upgrade soon. There are some issues should be noticed before you process.
1. If do-release-upgrade returns nothing found, you may want to use
2. Some servers will be stuck with “Updating database of manual pages” process. In my tests on about 20 servers, about 20% servers will pass it with no more than 2 minutes delay. More than half servers, mainly on Azure, stuck there for 20-40 minutes. During this time, around 100 GB data are read from disk with 100% CPU using, reported by Azure portal. I don’t know what it read. All my files on the server cost no more than 20GB disk space. One of my server, hosted on Azure, costs more than half day so far (and not finished yet), more than 200GB data read. One server failed in that step, SSH drop and cannot reconnect at all. Before this problem solved, I strongly NOT recommend to upgrade your product server.
Update: The one stuck on Azure resume to idle after 14 hrs, 626.14GB reading and 27GB writing. Due to dead SSH process, I have to try to reboot the server. But the server never come back online. A kernel panic captured by Azure console while booting:
Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/admin-guide/init.rst for guidance. CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-1010-azure #10-Ubuntu Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090007 06/02/2017 Call Trace: dump_stack+0x57/0x7a ? rest_init+0x50/0xb0 panic+0xfb/0x2d7 ? do_execve+0x25/0x30 ? rest_init+0xb0/0xb0 kernel_init+0xfb/0x100 ret_from_fork+0x35/0x40 Kernel Offset: 0x30000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
3. Upgrading will replace php 7.3 with 7.4. If some site is powered by php-fpm with Nginx, you may need to change your web site configuration file in Nginx available sites folder. All packages installed by pip3 will be dropped, not uninstalled properly. You may want to uninstall them if you don’t want to use it any more before upgrading system. Or, you can reinstall them after upgrading.