Diagnose & troubleshoot system start up issues-EX342
- Identify and resolve service failures affecting boot
to find service dependencies you can view the service systemd file at
/etc/systemd/system/
- check the configs file
systemctl status -l vsftpd
2. check all configurations related to a service
3. List dependencies
sysemctl list-dependencies rsyslog
- Regain root control of a system
You will have to modify the kernel line during boot time as follows:
Press e to edit the selected grub boot line
Add rd.break to the end of the line that has linux16 then press CTRL+X to boot the system with the grub information entered
Mount the file system
#mount -o remount,rw /sysroot
#chroot /sysroot
Change the root password
#passwd
Update the selinux labels
#touch /.autorelabel
Restart the system
- Troubleshoot boot issues
This is dependent of the type of bios that the system is running. You will need to identify what type of BIOS this system is running.
BIOS - GRUB
If the configuration files are missing run the following commands
#grub2-mkconfig -o /boot/grub2/grub.cfg
or reinstall it on a chroot environment on the right disk
UEFI - EFI
#grub2-mkconfig -o /boot/efi/UEFI/redhat/grub.cfg
- Identify hardware and hardware problems
There are different commands that can be used to identify the hardware running on the system
To get the CPU information
#lscpu
# dmidecode
To get DISK information
#lsblk
To get ISCSI disk information
# lsscsi
To get PCI devices
#lscpci
To see all the options for each command run the man command.
- Manage kernel modules and their parameters