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If another local administrator can still use sudo, log in with that account and run sudo passwd USER. If no administrator can log in, use the recovery method that matches the distribution and release: Ubuntu recovery mode, trusted live or installation media, or the documented Red Hat boot-time procedure. These methods grant full root access, so use them only on a server you own or are authorized to administer.
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Before changing anything, identify the distribution, release, storage layout, encryption status, and whether you can reach the machine’s console and boot loader. A command that is correct for RHEL 7 may be wrong for RHEL 9, Ubuntu, or Debian.
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Choose the least invasive recovery path
Start at the top of this list and stop as soon as you have a working administrator account.
| Path | Use it when | What it changes | Main constraint |
|---|---|---|---|
| Another sudo-capable account | A second local administrator can log in | Resets the affected password and can restore group membership | Requires a working account and valid sudo policy |
| Ubuntu recovery mode | The server reaches GRUB but no administrator can log in | Opens a root shell from the installed system | The recovery root filesystem may start read-only |
| Trusted live or installation media | The installed system will not provide a usable recovery shell | Mounts the installed filesystem and repairs it through chroot |
Requires console access and correctly identified partitions |
| RHEL boot-time recovery | No root login or sudo-capable account remains on Red Hat Enterprise Linux | Edits the boot entry and resets credentials before normal startup | The procedure differs between RHEL releases |
Also check whether the root filesystem is encrypted, whether GRUB is password-protected, whether Secure Boot restricts external media, and whether a cloud provider controls the console. If any of those conditions blocks local recovery, use the provider’s documented rescue workflow rather than improvising.
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Recovery preparation and safety checks
Confirm authorization and preserve data
Boot-loader and live-media recovery intentionally bypass normal login controls. Confirm that you own the machine or have written authorization to administer it. If the system is unstable, copy critical data from rescue mode before editing account files. Do not experiment on the only copy of a production filesystem.
Record the system identity
- Distribution and release, such as Ubuntu, Debian, RHEL 7, or RHEL 9.
- Whether the machine uses BIOS or UEFI and whether GRUB is visible during reboot.
- Root,
/boot, and EFI partition layout; uselsblk -ffrom a shell or live environment instead of guessing device names. - Whether full-disk encryption asks for a passphrase before the operating system starts.
- Whether the server is physically reachable or relies on a remote console supplied by a hosting provider.
Keep a recovery shell disciplined
In a root shell, every command runs with unrestricted privileges. Type the target username and device path carefully, avoid recursive deletion, and do not overwrite /etc/sudoers with an editor that can leave it syntactically invalid. Use visudo when changing sudo policy.
When another administrator still has sudo
This is the safest and fastest route because it does not alter the boot process.
- Log in to the working local administrator account.
- Confirm the account and sudo policy with
idandsudo -l. - Reset the affected account:
sudo passwd USER. ReplaceUSERwith the exact login name. - If the root password itself is lost on RHEL 9, a non-root member of the
wheelgroup can runsudo passwd root. - If the user was removed from the administrative group, restore the distribution-appropriate membership. On Ubuntu this commonly means
sudo adduser USER sudo; on Red Hat systems it commonly meanssudo usermod -aG wheel USER. Check the release’s policy before applying a group change. - Inspect the account’s login shell and expiry state with
getent passwd USERandsudo chage -l USER. - Validate any sudoers edit with
sudo visudo -c, then test a new login rather than relying on an already-open session.
Do not reset a password and assume authorization is fixed: a valid password, an interactive shell, group membership, and sudo policy are separate checks.
Ubuntu: use GRUB recovery mode
Ubuntu’s documented recovery route applies when neither root nor another local administrator can log in but the machine can reboot to GRUB.
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Open the recovery root shell
- Reboot the server. On many BIOS systems, hold the right Shift key to display GRUB; on many UEFI systems, press or hold
Esc. Remote consoles may expose a different key sequence. - Choose Advanced options for Ubuntu.
- Select the kernel entry ending in (recovery mode). Choose the normal kernel version unless a known kernel problem requires another entry.
- In the recovery menu, choose drop to root shell prompt.
- Recovery often mounts the installed root filesystem read-only. Remount it read-write before changing credentials:
mount -rw -o remount /.
Reset the account and, if necessary, sudo access
- Verify the target name with
cut -d: -f1 /etc/passwdor inspect the account directly withgetent passwd USER. - Set a new password:
passwd USER. - If the account should administer Ubuntu, restore its group membership with
adduser USER sudo. Avoid changing the root account merely because the user’s sudo membership was lost. - Check that the shell is valid, for example
/bin/bashor another installed shell, and inspect/etc/shellsif login still fails. - For a manually edited sudo policy, run
visudo -cbefore leaving the shell. - Type
reboot, then test a fresh console or SSH login after normal boot.
Ubuntu warns that this procedure gives a full root shell and can damage the system. Do not leave temporary boot edits in GRUB’s persistent configuration.
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Use live media when the installed system cannot reach a usable recovery shell, its boot files are damaged, or you need to copy data before repairing it. A writable Linux live USB flash drive is the usual physical medium. Use media you trust and create it from a verified image appropriate to the server’s architecture.
Identify and mount the installed system
- Boot the live or installation environment and open a terminal.
- List filesystems and labels:
lsblk -f. Do not copy a device such as/dev/sda1without confirming that it is the installed root partition. - Create a mount point and mount the root filesystem, adapting the device and path to the actual layout:
sudo mount /dev/ROOT_PARTITION /mnt. - If the installation has a separate
/boot, EFI system partition, or separate/home, mount each at its corresponding path below/mnt. An EFI partition normally belongs at/mnt/boot/efi. - If the filesystem is encrypted, unlock it with the proper recovery key or passphrase before mounting. Without that key, password commands cannot reach the installed files.
Enter the installed environment with chroot
Ubuntu’s LiveCdRecovery procedure describes entering the mounted installation with chroot /mnt. For a more complete repair shell, bind the virtual filesystems first:
sudo mount --bind /dev /mnt/dev
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount -t proc /proc /mnt/proc
sudo mount -t sysfs /sys /mnt/sys
sudo mount --bind /run /mnt/run
sudo chroot /mnt /bin/bashThe exact mount options vary with the live environment. If a bind mount reports that the target does not exist, create the directory under /mnt or use the simpler chroot /mnt route for a password-only repair.
Repair credentials inside chroot
- Confirm that you are operating on the installed system with
cat /etc/os-releaseandpwd. - Reset the account:
passwd USER. To reset root specifically, usepasswd root. - Restore the correct administrative group if needed, such as
adduser USER sudoon Ubuntu orusermod -aG wheel USERon Red Hat systems. - Check sudo syntax with
visudo -c. If the command is unavailable in the chroot, repair the file only with a known-good editor and validate it after reboot from a normal session. - On SELinux-enabled Red Hat installations, ensure relabeling is performed when the release procedure requires it; a common documented step after a boot-time password reset is
touch /.autorelabel.
Exit cleanly and reboot
- Leave the chroot with
exit. - Unmount the virtual filesystems and installed partitions in reverse order. If a graphical live session keeps a directory busy, close file browsers and terminals opened inside
/mntbefore retrying. - Reboot, remove the USB when prompted, and test the repaired account in a normal boot.
Mounting the wrong partition can make a successful password change appear ineffective because you edited another operating system. Always verify /etc/os-release inside the chroot.
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Red Hat Enterprise Linux 9
RHEL 9 documents a special boot-time mode for the case where root login is unavailable and no non-root account can use sudo. The broad sequence is consistent, but kernel parameters and initramfs behavior can vary by minor release, so use the RHEL 9 procedure matching the installed release.
General sequence
- Reboot and interrupt GRUB.
- Highlight the normal kernel entry and press
eto edit it temporarily. - Append the recovery parameter specified by the RHEL 9 documentation for that release to the Linux kernel command line.
- Boot the edited entry with the key combination shown by GRUB, commonly
Ctrl+XorF10. The edit applies only to this boot. - At the initramfs or special-mode shell, remount the installed system read-write as directed by the release procedure, enter it with
chrootwhen required, and runpasswd rootorpasswd USER. - Preserve SELinux labeling. RHEL procedures commonly require
touch /.autorelabelbefore rebooting after a password reset. - Exit the shell and reboot. Remove the temporary kernel edit; it is not a permanent GRUB setting.
If the reset succeeds but login still fails, check the account’s shell, lock state, PAM policy, and sudo configuration from a normal boot. A root password reset does not automatically restore a deleted administrator account.
RHEL 7: installation media or rd.break
RHEL 7 documents two approaches: booting installation media and stopping early with rd.break. The latter interrupts the handoff from initramfs to systemd.
Using rd.break
- At GRUB, highlight the kernel entry and press
e. - Find the line beginning with
linuxorlinux16and appendrd.break. - Boot the temporary entry.
- Remount the installed root under
/sysrootread-write:mount -o remount,rw /sysroot. - Enter the installed system:
chroot /sysroot. - Reset the password with
passwd rootorpasswd USER. - For SELinux systems, mark the filesystem for relabeling with
touch /.autorelabel. - Run
exitto leave the chroot, thenexitagain to leave the break shell, and reboot.
Because the kernel-line change is temporary, it disappears after reboot. If the server uses a different storage layout or an encrypted volume, unlock and mount it according to the installation’s configuration before running passwd.
Using RHEL installation media
Boot the installation disk and select its rescue option. The rescue environment may locate and mount the installed system for you, after which you can chroot into the mounted root and run the same account commands. Confirm the mount point and inspect /etc/os-release before editing.
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Older Red Hat rescue, single-user, and emergency modes
Older Red Hat documentation distinguishes three modes that are not interchangeable:
- Rescue mode is useful for accessing files when the installed system cannot complete a normal boot.
- Single-user mode provides a restricted administrative environment suitable for a password reset on systems that support it.
- Emergency mode is more minimal and mounts the root filesystem read-only, so you must remount it read-write before changing anything.
Do not assume an older GRUB recipe works unchanged on a newer release. If a mode presents a read-only root, use the remount command appropriate to that environment, verify the target filesystem, and follow the release-specific Red Hat instructions.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Debian: the root account may be disabled by design
Debian commonly disables direct root login during installation and gives the first created user administrative ability through sudo. In that configuration, a lost user password or removed sudo authorization is not solved by merely setting a root password: there may be no usable root password at all.
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Repair the first user’s access
Use Debian recovery mode if GRUB is available, or a trusted live medium and chroot if it is not. Reset the affected user’s password with passwd USER, then restore that user’s sudo authorization according to the installed policy. Inspect /etc/sudoers and files under /etc/sudoers.d with visudo -c. Create a root password only if your security policy specifically requires direct root access; keeping root disabled and using sudo may be the safer Debian model.
Verify the repair after normal boot
A password command can succeed while another account setting still blocks access. Perform these checks after reboot:
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- Log in with a new session, not an old SSH connection.
- Confirm the account’s shell with
getent passwd USER; a shell set to/usr/sbin/nologinor a nonexistent path prevents interactive login. - Check lock and expiry state with
passwd -S USERandchage -l USER. - Confirm group membership with
id USER. Group changes may require logging out and back in before they take effect. - Run
sudo -l -U USERfrom an administrator account and validate policy syntax withvisudo -c. - Test the exact access method you need: console login, SSH, or the service account’s noninteractive operation.
- Review authentication logs for a rejected login, expired account, denied shell, or PAM error if the new password still fails.
When the standard procedures do not apply
Encrypted root storage
You cannot repair files inside an encrypted root volume until it is unlocked. Obtain the recovery passphrase or key from the authorized owner. Do not erase or recreate the volume in an attempt to bypass it.
GRUB protection or inaccessible console
A GRUB password, a server with no physical console, or a remote-only machine can prevent the Ubuntu and RHEL boot paths. Use the organization’s out-of-band console or the hosting provider’s documented rescue process. Provider-specific behavior is configuration-dependent.
Secure Boot and external media
Secure Boot policy may reject a live image or unsigned boot component. Use a trusted, signed recovery image approved for the machine, or follow the platform’s documented enrollment and recovery procedure.
The filesystem will not mount read-write
Stop changing passwords until storage is healthy. A filesystem that remains read-only may have errors, failed hardware, or an active encryption or RAID problem. From a rescue environment, copy critical files first and run the distribution-appropriate filesystem checks only on an unmounted filesystem.
Prevent a repeat lockout
- Keep at least two tested administrator accounts, each with individually managed credentials.
- Store recovery keys, console access details, and the distribution release in an authorized runbook.
- Test a recovery boot on non-production hardware so the team knows how its GRUB, encryption, and remote console behave.
- Use a password manager or approved SSH-key process, with a documented way to revoke lost credentials.
- Review sudo policy after staff or role changes and validate it with
visudo -c. - Keep current backups and verify that a rescue environment can read the backup target.
Frequently Asked Questions
Can I reset a Linux password without knowing the old one?
Yes, if you have authorized root access through another sudo-capable account, the distribution’s recovery mode, or trusted live media. These methods are administrative recovery paths, not ordinary user password changes.
Why did changing the password in a live USB environment have no effect?
The installed root partition may not have been mounted, or the wrong partition may have been mounted. Inside the chroot, verify /etc/os-release and the account entry before running passwd.
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Check the account’s group membership, sudoers syntax, shell, lock state, and expiry. On Ubuntu the administrative group is commonly sudo; on Red Hat it is commonly wheel, subject to the system’s policy.
Is a root-password reset possible on an encrypted server?
Only after the encrypted volume has been unlocked with its authorized key or passphrase. Boot recovery cannot bypass encryption.
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