Check permissions on your home folder. Make sure everything is owned by your new username.
I had a separate partition mounted on /home on my old system. I remounted the same partition at /home on the new system, and got the same bootloop issue. The problem was that the old permissions were for 1001:1001, not (newuser):(newuser). Had to log into a TTY and chown (newuser):(newuser) -R /home/(newuser) to get everything working.
[see:https://lemmy.world/post/34365607/18768530]
I tried logging in with tempuser and remembered that I have no idea how to access the files on my main user. In the file manager the home folder for said user isn’t accessible, and I assume that’s because I set it to be encrypted when setting it up. Thus I can’t access the files to copy them over to a new user or anything. Also, I assume I wouldn’t be able to rename the homedir as such, and don’t know where to start checking or changing user settings and permissions and such.
First, check if you can login, with your new user, on the Linux console (i.e. Ctrl-Alt-F1 through F7). If you can, the username change probably went through correctly. Report back if you cannot login via console or you get warnings/errors.
Your login session does automatically terminate if the session process for Cinnamon exits, booting you back to GDM (or whatever login manager you have). So probably the Cinnamon session process, started by GDM, craps out for some reason. The reason is probably, I suspect, that it cannot access or cannot find some file it wants to open.
Check ~/.xsession-errors, it might tell you what went wrong.
Also check the permissions of your home folder, the files in your home folder, and check if you correctly set up the symbolic link from /home/olduser to /home/newuser as the guide suggests.
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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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