[SOLVED] Cannot use sudo after changing my user password. Cannot access root in any other manner either.

gebees · 10-20-2019, 05:27 PM

I am running Mint 18.1 on a Toshiba Satellite P75-A and access grub bootloader via ESC at boot. My username is no longer a member of sudo group though it is a member of adm. I am the only user of this computer, and my network is a home network with ethernet and wifi and, typically, only one other user.

Keith Hedger · 10-20-2019, 05:35 PM

use a live cd or similar boot using it and reset your user password google to find exact solution for your distro

Firerat · 10-20-2019, 06:03 PM

the problem is not with the password
it is the fact the the membership of sudo group is lost

I assume

Code:

usermod -G adm gebees

the problem is, -G on its own flushes all other group memberships

man usermod

Quote:

-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no
intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option.

If the user is currently a member of a group which is not listed, the user will be removed from the group. This behaviour can be
changed via the -a option, which appends the user to the current supplementary group list.

to fix, you need to boot a liveCD, mount the root partition, chroot to it and then fix the users group

there was a similar thread not so long ago, I'll see if I can find it

Firerat · 10-20-2019, 06:16 PM

I was hoping I could find it quickly, but no

the reason I wanted to link it was I think they managed to get to root account by booting recovery mode from grub
Which is easier than my suggestion of chroot with a liveCD

Firerat · 10-20-2019, 06:28 PM

found it

see @michaelk post for how to readd sudo

https://www.linuxquestions.org/quest...5/#post6029860

BW-userx · 10-20-2019, 07:34 PM

go live use that root user to do what you got a do.

gebees · 10-20-2019, 07:50 PM

I've just gotten ready to try the boot-from-ISO solution. This method gets me directly to my current user name and allows me to work on it without any other password. Thanks for that.

Firerat · 10-20-2019, 07:58 PM

you need to thank @michaelk in the other thread

I had always assumed that the recovery from grub method prompted you for password

I have a memory of needing root password when a boot failed and I needed to enter maintenance mode

gebees · 10-20-2019, 10:36 PM

In using the Mint 18.2, Cinnamon 64 bit ISO to boot from USB stick, I found that, sadly, I could not read my hard drive such that my booted OS could work in any way with any user management commands such as adduser, passwd, users etc. Nor was sudo useable with my login credentials. Anyway, researching more, trying again.
Help I've received has clarified and expanded my work to fix this issue. Thanks. Any further ideas are welcome.

Firerat · 10-20-2019, 10:53 PM

did the boot to recovery not work?

I have quoted the post I linked earlier

you should replace g41m-combo with your user name

if the below does not work, I can probably walk you through chroot via a liveCD

Quote:

Originally Posted by michaelk

To elaborate as far as I know the only way to accomplish the above is boot into recovery mode and select drop to a root shell prompt. The root partition is mounted but as read only. To mount it read/write use the mount command.

mount -o remount,rw /

To restore sudo group

adduser g41m-combo sudo

To quit recovery mode type exit and then reboot.

I have not booted into recovery mode in a long time so I can't not confirm exact wording of recovery mode. I also assume that Mint works the same as Ubuntu.

if the above fails

I'm guessing Mint is lvm2 and not "traditional" partitions
to confirm I will need to output of

Code:

lsblk

you won't need root to run that, ( and it should be installed by default )

gebees · 10-21-2019, 11:34 AM

I booted from an ISO of my Mint as well. No happiness there because I could not chroot, if that makes sense, and when I ran fdisk -l, the booted OS was denied access,'...permission denied.' I'm thinking of attempting the ISO boot with an Ubuntu ISO. It seems that the Ubuntu OS may have more luck with the fdisk -l and the chroot. Regarding the boot to recovery 'failure', I believe that I had set a root password some time ago, but the password that I remember does not work when- and wherever I attempt to use it.

gebees · 10-21-2019, 11:40 AM

~ $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
sda 8:0 0 698.7G 0 disk
├─sda2 8:2 0 690.2G 0 part /
├─sda3 8:3 0 7.9G 0 part [SWAP]
└─sda1 8:1 0 512M 0 part /boot/efi

BW-userx · 10-21-2019, 12:05 PM

chroot just do not do the install-grub part and try dealing with your issue how ever it needs to get done, remember to change the parts that reflect your system.

https://zeldor.biz/2010/12/install-grub-from-chroot/

efi grub stuff jic
https://wiki.debian.org/GrubEFIReinstall

Firerat · 10-21-2019, 12:11 PM

yeah, you need root

https://linuxmint-installation-guide...e-live-session

ok, so it isn't lvm ( I assumed that was the default ( like CentOS ) these days, I guess it is still optional )

boot your live CD and open a terminal

Code:

mkdir /tmp/mnt
sudo mount /dev/sda2 /tmp/mnt
# no password, see link above just hit enter 
sudo chroot /tmp/mnt
# you should now be root on your install!
adduser yourusername sudo
exit # to get out of the chroot
sudo umount /tmp/mnt

then reboot

you should now have access to sudo once more

consider adding your username

Code:

sudo visudo

Code:

<snip>
# User privilege specification
root    ALL=(ALL:ALL) ALL

copy that root line, subsituting your username
this way should you lose sudo group membership you can still use sudo

you might also like to think about adding a password for root

Code:

sudo passwd root

but since you have explicitly added your username to sudoers you should not need that

BW-userx · 10-21-2019, 12:28 PM

that last part, I'd add root passwd this way one can still get in via root in case user cannot.