Recover from “Username is not in the sudoers file. This incident will be reported” on WSL2

I tried to improve WSL2 memory consumption improvement. I found a workaround on this issue.

WSL 2 consumes massive amounts of RAM and doesn't return it · Issue #4166 · microsoft/WSL

However, through the process, I mistook. I can’t use sudo command, anymore. How to fix it? Since I can’t be root without sudo How to fix it?

Solution

WSL2 have a command to manage it. Start command prompt on Windows10.

> wsl --user root

Now you can login the WSL2 as a root . The issue was happened, since I modified /etc/sudoers file with visudo command. The problem is, by default, visudo command start nano editor that I’m not familiar with. It has two option for save DOS and MAC . I though. No. I’m using Linux How can I choose the one. Mac is closer to Linux, so I choose it. These process adds special character on that file. I confuse a lot about it. Even if I correctly configured it, it still emit error for each line except for comment lines. There is no clue.

NOTE: My friend find a Stack Exchange post about this topic.

root@DESKTOP-SDE49UK:/etc/sudoers.d# visudo
>>> /etc/sudoers: syntax error near line 7 <<<
>>> /etc/sudoers: syntax error near line 8 <<<
>>> /etc/sudoers: syntax error near line 9 <<<
>>> /etc/sudoers: syntax error near line 10 <<<
>>> /etc/sudoers: syntax error near line 12 <<<
>>> /etc/sudoers: syntax error near line 14 <<<
>>> /etc/sudoers: syntax error near line 16 <<<
>>> /etc/sudoers: syntax error near line 18 <<<
>>> /etc/sudoers: syntax error near line 19 <<<
>>> /etc/sudoers: syntax error near line 20 <<<
>>> /etc/sudoers: syntax error near line 22 <<<
>>> /etc/sudoers: syntax error near line 23 <<<
>>> /etc/sudoers: syntax error near line 25 <<<
>>> /etc/sudoers: syntax error near line 26 <<<
>>> /etc/sudoers: syntax error near line 28 <<<
>>> /etc/sudoers: syntax error near line 30 <<<

You can use this command to make sure there is no special character

$ cat -A /etc/sudoers

Then, convert it to unix format file to fix the issue of /etc/sudoers .

$ apt install dos2unix
$ dos2unix /etc/sudoers

/etc/sudoers is in charge of manage sudo configuration. It should be edited by visudo . Since this operation could be very dangerous. Once mis configured, I can’t login anymore. So that we use visudo . It helps us to check the modify is correct or not. I recommend to change it from nano to vi. So, before modifying it you can do

$ update-alternatives --config editor

You can choose vim now.

Then

$ visudo

You can successfully modify it. For the grammar of visudo You can refer this page:

Using the Sudoers File to Give Users Root Privileges on Ubuntu 18.04 | 16.04 | Website for Students

FYI: This is the default /etc/sudoers file on WSL2 (18.04, 20.04). You might want to rollback to this.

Finally, you can use this command to reboot

$ wsl --shutdown

Then restart your WSL2. You will find you can use sudo again.

Resources

Linux and character encoding (Japanese)

Linux上のファイルの改行文字を確認する方法 - Miuran Business Systems