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I am unable to determine the cause of this, but the day prior when using su to enter my password for installing an application through the terminal, the authentication has been successful. So far, I am uncertain on how to resolve this issue. I use a Fedora 29 GNOME OS.

[Machine-Replicator@localhost ~]$ su
Password: 
su: Authentication failure
Rui F Ribeiro
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Luna_II
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1 Answers1

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The su command does not accept your password. You must use the target user's password, which in your example shown is the root password.

Are you perhaps muddling su with sudo, which does take your own password for authentication?

roaima
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  • Alternatively, if it is a root command prompt you're after, `sudo su` or `sudo -i` – SHawarden Jun 03 '19 at 22:48
  • @SHawarden, NEVER `sudo su`. What that says is effectively, "_Hello `sudo`, please may I have root... ah thank you. Hello `su`, even though I'm now already root please may I have root... thank you._" Just use `sudo -s`. – roaima Jun 03 '19 at 22:57
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    Thank you, sudo -s was able to resolve my problem. I'm not entirely certain how or why this worked, but I'm fairly new to the Linux operating system and trying to understand how to use it. Thanks again. – Luna_II Jun 04 '19 at 02:51
  • I'm confused, I'm sure I have been switching to root with "su" then getting a prompt for root password for decades. Have I totally forgotten how this works? Or has it changed between Fedora 27 or 31 or 33, and 37?? – Swiss Frank Mar 17 '23 at 20:12
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    @SwissFrank that's right. `su` requires the target user's password. `sudo` usually expects the initiator's password – roaima Mar 17 '23 at 20:46
  • @roaima to be clear, I AM typing simply "su" then the root password ( think), and NOT being able to log in. "sudo -s" works however. I am wondering though on Fedora 37 clean install, maybe root password is not set or is set funny, but it gave my personal account permission to su to root without any input?? – Swiss Frank Mar 18 '23 at 15:25