It's inevitable that something will go wrong with a Linux installation that needs to be fixed. The best way of doing this is booting into the emergency target, which still prompts for a password but doesn't mount the root filesystem. If the root password has to be retrieved then you need to do an administrator password reset.
- [Instructor] To boot up a system…that is not functioning properly,…we can use a systemd emergency target.…In the emergency target,…it doesn't try to mount the root file system.…This would be the correct target…if the root file system were having problems.…Note that the emergency target still requires a password.…To change temporarily into the emergency target,…double click the centos7-ks VM…in the virtual machine manager window,…and click the console button on the toolbar.…Now, click on the power button to start it up.…
At the GRUB prompt, press any key to enter the GRUB menu.…We could choose a different kernel entry here…if we wanted to, using the up and down arrow keys.…This gives us the ability to boot into an older kernel…if an update didn't go well.…Let's select the most recent kernel,…which will be at the top.…Then press the E key for edit.…Go down to the line that includes vmlinuz,…and then press the End key to go to the end of the line.…Type in systemd.unit=emergency.…
The line that includes vmlinuz is the kernel line,…
Author
Grant McWilliams
Released
8/31/2017Instructor Grant McWilliams covers network and internet services administration, kernel management, and intrusion prevention. He shows how to make your systems more efficient with virtualization, manage users and groups, and lock everything down with SELinux mandatory access control. Plus, get access to 25 PDF "cheat sheets" and 100 practice questions so you can solidify and test your knowledge.
- Installing Linux on a physical machine
- Managing systemd services
- Managing reoccurring jobs with cron
- Limiting system access
- Configuring networking
- Creating, editing, and moving files and directories
- Analyzing text with grep and regular expressions
- Installing software and packages
- Managing the kernel
- Managing users, accounts, and groups
- Setting permissions
- Using access control lists
- Securing Linux with SELinux
- Accessing Linux remotely
- Configuring local storage
Skill Level Intermediate
Duration
Views
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Introduction
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Welcome57s
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What you should know3m 45s
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About Red Hat Certifications2m 52s
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1. Deploy Systems
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Managing virtual machines6m 42s
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2. System Config and Services
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Get systemd service status3m 56s
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Manage systemd services2m 33s
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Configure networking3m 52s
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Manage one-time jobs with at4m 16s
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3. Essential Tools
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Archive files using tar4m 40s
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Compress files and archives4m 14s
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Create files and directories5m 18s
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Copy files and directories5m 48s
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Move files and directories4m 59s
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Create hard and soft links4m 55s
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Introduction to vim3m 33s
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Editing text with vim2m 45s
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Reading the system journal3m 26s
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4. Manage System Software
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Query with RPM7m 14s
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RPM query formatting6m 5s
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Overview of yum2m 20s
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Get info on package groups5m 15s
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Search for packages1m 47s
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Install and remove packages6m 59s
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Manage OS updates6m 48s
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Update the kernel4m 29s
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Manage kernel modules5m 18s
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5. Users and Accounts
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Modify local user accounts4m 57s
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6. File Access Control
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File and directory modes1m 19s
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Read access control lists3m 36s
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Set access control lists5m 49s
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Delete access control Lists4m 15s
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7. Manage Security
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Manage firewalls3m 15s
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8. Accessing Linux Remotely
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Configure Secure Shell2m 36s
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9. Configure Local Storage
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Conclusion
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Next steps1m 20s
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Video: Boot into the emergency target