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  • How to reset or change lost root password in RHEL / CentOS 7

    In Red Hat Enterprise Linux/Cent OS 6 changing root password was quiet easy (well it is easy if you know the steps and it is hard if you don't)

    For RHEL / CentOS 7 the steps are completely different and a little trickier than it was in older RHEL versions.

    In this article I will show you the steps to reset your root password using rd.break

    NOTE: I hope you have console access to your Linux box as without this you cannot reset the password using an ssh client.
    Reboot your Linux box to the boot menu as shown below

    Edit the primary boot loader in the GRUB menu as for me you can see I only have one kernel installed to I will press "e" to enter into edit mode

    which will bring you below menu
    setparams 'Red Hat Enterprise Linux Server (3.10.0-693.el7.x86_64) 7.4 (Maipo)'

            load_video
            set gfxpayload=keep
            insmod gzio
            insmod part_msdos
            insmod xfs
            set root='hd0,msdos1'
            if [ x$feature_platform_search_hint = xy ]; then
              search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  af0be92e-0721-46b8-affd-60f9baff3652
            else
              search --no-floppy --fs-uuid --set=root af0be92e-0721-46b8-affd-60f9baff3652
            fi
            linux16 /vmlinuz-3.10.0-693.el7.x86_64 root=/dev/mapper/rhel-root ro rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet net.ifnames=0 systemd.unit=emergency.target
            initrd16 /initramfs-3.10.0-693.el7.x86_64.img

          Press Ctrl-x to start, Ctrl-c for a command prompt or Escape to 
          discard edits and return to the menu. Pressing Tab lists       
          possible completions.

    Look out for the kernel line i.e. below one for me
    linux16 /vmlinuz-3.10.0-693.el7.x86_64 root=/dev/mapper/rhel-root ro rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet net.ifnames=0

    Remove "rhgb quiet" and add "rd.break" in the last as shown below
    linux16 /vmlinuz-3.10.0-693.el7.x86_64 root=/dev/mapper/rhel-root ro rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap net.ifnames=0 rd.break

    rd.break will stop the boot procedure before mounting the filesystem wherein all the supporting modules are loaded and with a valid shell.
    Press "Ctrl +x" to boot your box with the new changes

    As you see now you have a shell and you were not prompted for root password

    Next you must remount your filesystem with read write permission as currently you have logged in with read only mode for root filesystem
    switch_root:/# mount -o remount,rw /sysroot

    Next we need to move the content of sysroot from chroot to normal root environment
    switch_root:/# chroot /sysroot





    Now you are ready to set your password. You can use below command to set the password. Replace "mynewpassword" with your new password followed by the username i.e. "root"
    sh-4.2# echo mynewpassword | passwd --stdin root

    Next we need to tell selinux that it needs to do relabelling or else our changes will be gone after reboot, for this create a new autolabel file using below command
    sh-4.2# touch /.autorelabel

    You are all done now. Next press "Ctrl +D" twice to exit the window followed by a reboot

    Next once your node is UP, try to login with your new password

    I hope the article was useful.

    Deepak Prasad

    Deepak Prasad is a techie and an author who is still trying to survive in this IT generation with very little knowledge he has on Linux/Unix, VMware, SAN Storage, Automation, networking etc

    You can follow him on Facebook or Google+

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    How to reset or change lost root password in RHEL / CentOS 7 How to reset or change lost root password in RHEL / CentOS 7 Reviewed by Deepak Prasad on Saturday, April 14, 2018 Rating: 5

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