Arch Linux

quyet

Member

Registered: 2026-06-11

Posts: 4

[SOLVED]Get su: Authentication failure when su with right password

I logged in successfully yesterday, checked password in plain text and use copy/paste to ensure typing it correctly. I also cannot log in from TTY, get Login incorrect.

Before this happens, I remember updating & installing base-devel package. I encountered this problem when makepkg an AUR. I also notice that sudo is installed and makepkg output says my user is not a sudoer.

Please give me a point to find the reason why it happens. I have not done any password reset, and do not need to reset it right now. Thank for your help!

Last edited by quyet (2026-06-12 14:01:51)

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,224

Re: [SOLVED]Get su: Authentication failure when su with right password

Su will ask you for the root password, not yours.
https://wiki.archlinux.org/title/Sudo

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quyet

Member

Registered: 2026-06-11

Posts: 4

Re: [SOLVED]Get su: Authentication failure when su with right password

Thank seth, I type root password, my user password is not set. But when I logged in to my user then try su quyet & enter a blank password, it returns su: Authentication failure. In SDDM, I just enter to login to my user.

dimich

Member

From: Kharkiv, Ukraine

Registered: 2009-11-03

Posts: 647

Re: [SOLVED]Get su: Authentication failure when su with right password

I encountered this problem when makepkg an AUR. I also notice that sudo is installed and makepkg output says my user is not a sudoer.

What exactly do you do with makepkg? How do you run it?
Makepkg doesn't require root privileges to build a package, only to install it or handle dependencies with pacman.

If sudo is installed, regardless of whether your user is in sudoers or not, makepkg tries to use sudo. If sudo isn't installed, it falls back to su.
You can either:
Just build a package with makepkg but don't install it with the same command. Install it manually as root whatever method you use to gain root privileges.
or
Add your user into sudoers.
or
Uninstall sudo. Makepkg will use su. Of course, you have to enable root password authentication in this case.

cryptearth

Member

Registered: 2024-02-03

Posts: 2,195

Re: [SOLVED]Get su: Authentication failure when su with right password

my user password is not set.

i doubt that this is even a valid possible option on linux - as without a password the account is either locked or disabled

dimich

Member

From: Kharkiv, Ukraine

Registered: 2009-11-03

Posts: 647

Re: [SOLVED]Get su: Authentication failure when su with right password

i doubt that this is even a valid possible option on linux - as without a password the account is either locked or disabled

Nope, a user may have UNIX password disabled but login with other authentication methods.

cryptearth

Member

Registered: 2024-02-03

Posts: 2,195

Re: [SOLVED]Get su: Authentication failure when su with right password

Nope, a user may have UNIX password disabled but login with other authentication methods.

well ... today I learned

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,224

Re: [SOLVED]Get su: Authentication failure when su with right password

I type root password, my user password is not set. But when I logged in to my user then try su quyet & enter a blank password… In SDDM, I just enter to login to my user.

Your root password is NOT the (empty) user password and it is most likely not blank either.

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quyet

Member

Registered: 2026-06-11

Posts: 4

Re: [SOLVED]Get su: Authentication failure when su with right password

What exactly do you do with makepkg? How do you run it?

I run makepkg --syncdeps & get quyet is not in the sudoers file.

Add your user into sudoers.

I then type visudo & get visudo: /etc/sudoers: Permission denied
Finally, I type su, type the password & get su: Authentication failure

i doubt that this is even a valid possible option on linux - as without a password the account is either locked or disabled

I used useradd to add my user, then passwd with -d option to make it empty, not exactly like having no password. I misunderstand, sr you!

Your root password is NOT the (empty) user password and it is most likely not blank either.

Yes, I only have root password, & this is the only password I type everytime.

quyet

Member

Registered: 2026-06-11

Posts: 4

Re: [SOLVED]Get su: Authentication failure when su with right password

Sr all, I must admit that I forgot the password . I'm very surprised that I just typed it correctly yesterday. Now I found it, thank for all your support!