Understanding Troubleshooting Modes

The boot procedure can be interrupted in various ways:

Kernel arguments should be used to interrupt the boot process if there is an issue loading the current kernel version

If the kernel is loading, but it is necessary to load the system right after the kernel is loaded, use rd.break

If there is an issue with loading into a target, use either emergency.target or rescue.target

Changing the Root Password

rd.break enforcing=0
mount -oremount,rw  /sysroot
chroot /sysroot
touch /.autorelabel
sh-4.2# exit
exit
restorecon /etc/shadow

setneforce 1

Troubleshooting Filesystem Issues

Real filesystem corruption does occur, but most often automatically fixed

Problems occur when making typo’s in /etc/fstab

To repair these type of issues, remount the filesystem in a read/write state and edit /etc/fstab by booting into the Emergency Target

Fragmentation can be fixed by:

Troubleshooting Networking Issues

Common Network Issues

Use ip a to check the current DNS configuration on the system network devices

Use ip a d [IP_ADDRESS] dev [DEVICE_NAME] to remove any unwanted IP Addresses

Use ip a a dev [DEVICE_NAME] [IP_ADDRESS] to add an IP Address

Use ip route show to list the current network routes, and ip route add default via [IP_ADDRESS] to add a default route

To make changes persistently, use nmtui

Use dhclient to renew the IP Address from the DHCP server

Troubleshooting Performance Issues

Focus on the four key area’s of performance:

Utilize top to obtain an overview of the system’s overall health, and either renice or kill processes

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