Extra chars in `/etc/hosts`

[elsaco]

Version

Microsoft Windows [Version 10.0.19045.2604]

WSL Version

• WSL 2
• WSL 1

Kernel Version

5.15.90.1

Distro Version

AlmaLinux 9.1

Other Software

No response

Repro Steps

Check system logs for bad address at /etc/hosts kind of message (i.e. journalctl --grep "bad address")

Expected Behavior

No extra characters added to /etc/hosts

Actual Behavior

<feff> added to /etc/hosts. Top pane show Windows' hosts file content. The bottom is WSL, Use view to display as cat or bat won't show it. Notice line 6:

Diagnostic Logs

No response

Thanks @elsaco, as a sanity check wsl --version are you on?

None of us have been able to repro this. If you have any clues that'd be appreciated.

[elsaco]

FEFF looks like a BOM signature. I can't tell where/how it was added to the /etc/hosts but it's gone now. Trying to setup dnsmasq would trigger invalid entry in host file error messages, otherwise I wouldn't notice it. Can't repro now.

[xanderificnl]

I'm seeing the same issue. You might be able to reproduce this issue by displaying non-printable characters, i.e. look for M-oM-;M-? by running cat -A /etc/hosts

Windows' host file starts with the offending character and it seems like it's being appended (albeit stripped from comments) to /etc/hosts - if I'm right, the solution is to remove the UTF-8 BOM from Windows' host file before appending to /etc/hosts

Get lines 6-9 from /etc/hosts and display non-printable characters

$ sed '6,9!d' /etc/hosts | cat -A
M-oM-;M-?$                                                                                      # <FEFF>
192.168.88.254^Ihost.docker.internal$
192.168.88.254^Igateway.docker.internal$
127.0.0.1^Ikubernetes.docker.internal$

Reformat Windows' host file

$ sed -f w32hosts.sed /mnt/c/Windows/System32/drivers/etc/hosts | cat -A
M-oM-;M-?$                                                                                      # <FEFF>
192.168.88.254^Ihost.docker.internal$
192.168.88.254^Igateway.docker.internal$
127.0.0.1^Ikubernetes.docker.internal$

w32hosts.sed

# Strip comments from
s/#.*//g
# Remove carriage returns
s/\r//g
# Remove empty lines
/^$/d
# Ensures spaces are tabulars
s/[[:space:]]/\t/g

[Tatsh]

Is Docker Desktop to blame for this? I do not think the file normally has a BOM at all. None of the other text files in the Windows etc directory have it.

[AnixPasBesoin]

This issue is still prevalent, any fix?

[OneBlue]

Fixed in 2.6.0