Boot into Single User-mode

Single user mode is a mode in which a multiuser computer operating system boots into a single superuser. It is mainly used for maintenance of multi-user environments, Basically single user mode in unix based systems is known as runlevel 1.

Some tasks may require exclusive access to shared resources, for example running fsck on a network share or to retrieve a lost superuser password or any maintenance task.

For gaining access to #(root) prompt what you need to do is ?



  • Once your machine is booting, for getting access to # prompt your just need to edit the bootloader i.e. in case of RHEL6 its GRUB (GRand Unified Bootloader). 


  • Once your machine is booting just press a key couple of time so that you are brought to the GRUB menu.



  • The GRUB menu appears like the image shown below:


  • The values which are show in this window are the kernerl(s) which are installed in your machine.

    • Use the cursor keys to switch between kernels (if you have more than 1 installed) to choose the one you want to boot.
    • Press "e" to edit the kernel commands before booting.
    • Press "a" to modify the kernel arguments.
    • Press "c" to go to a command-line,  for extended troubleshooting etc.
    • Once you pressed "e" while the kernel of your choice is highlighted, you get a second menu like the one shown on below screen.



    • Highlight the second line which starts with kernel /vmlinuz_______, Just press "e".

    • It will bring to a screen in which you just need to press a space once followed by 1 or single.

    • Make sure to hit “enter” to actually add the argument and to return to the boot menu. Escape does get you back to the same menu as well, but it does not add the argument, so your work will be undone actually.
    • Once you are back to your previous menu just press "b" to boot the kernel, Once your OS is booted you can see a screen something like this:

    • Now at the bottom of you screen you can see that you are on # prompt i.e. root prompt, Just type a command: passwd this will change your root password.
      • [root@sunny1 /]# passwd





      Comments

      Post a Comment

      Popular posts from this blog

      Installing Tomcat8 on RHEL6

      Image
      Apache-HTTP v/s Apache-Tomcat: The basic difference is Apache-Tomcat is written in Java but Apache-HTTP is written in C. Apart from this Apache-Tomcat is used as a webserver as well as to deploy Java Servlet's and JSP's [Java server pages] so basically Apache-Tomcat is used to serve Java Technologies whereas Apache-HTTP is used to serve HTTP. Prerequisites: Appropriate version of JRE [Java run-time environment] for instance jre1.7 is required to run tomcat-8[.X.X]. Tomcat binaries, for version 8 check this link . Sudo/Root access to the machine. Step1: Install JRE Download JRE from Java's official website. You can keep Java at any location but for my ease I have kept both Tomcat and Java in /opt. # cd /opt # cp jre-7u45-linux-x64.tar.gz . # tar -zxvf jre-7u45-linux-x64.tar.gz  The above command will create a folder with JRE binaries. In my case it was "jre1.7.0_45". Now set JRE_HOME [Required by Tomcat] and PATH. export JRE_HOME=/opt/jre1.7.
      Read more

      Manage existing resources via Helm

      Manage existing resources via Helm Helm is really a very powerful tool for managing Kubernetes objects. With a single command, we can install or upgrade multiple related Kubernetes entities. Let's say we want to install any chart from the helm registry, we just need to type in the below command and helm will do the heavy lifting for us. $ helm install [RELEASE_NAME] [REPO]/[CHART] But below post is not about the basics of helm or how to install or upgrade a chart, etc. It's been a long time since I wrote anything, so I just thought to write something about what new I learned today :)  While installing one of my charts, I encountered below issue: Error: INSTALLATION FAILED: rendered manifests contain a resource that already exists. Unable to continue with install: StorageClass "demo-sc" in namespace "" exists and cannot be imported into the current release: invalid ownership metadata; label validation error: missing key "app.kubernetes.io/managed-by&qu
      Read more

      Configuration and setting-up of AIDE on RHEL6

      AIDE is a powerful package for checking integrity of files on a machine/system. Prerequisites : Just aide package. [root@sunny ~]# yum install aide -y Loaded plugins: refresh-packagekit, rhnplugin This system is not registered with RHN.                                                                         RHN support will be disabled. Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package aide.x86_64 0:0.14-3.el6 set to be updated --> Finished Dependency Resolution Dependencies Resolved ================================================================================  Package         Arch              Version               Repository        Size ================================================================================ Installing:  aide            x86_64            0.14-3.el6            local            123 k Transaction Summary =============================================================
      Read more