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RHCSA - Red Hat Certified System Administrator: Qs & As
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RHCSA - Red Hat Certified System Administrator: Qs & As
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RHCSA - Red Hat Certified System Administrator: Qs &As
Commands/process to reset root password Right Ans - on boot:
select most recent kernel
`e` to edit
goto line with linux16, add `rd.break` to end of line
`ctrl+x` to continue boot to rd rescue mode
remount /sysroot as readable (defaults to read only in rd rescue mode):
`mount -o remount,rw /sysroot`
load the target env with:
`chroot /sysroot`
reset the password with:
`passwd root`
fix selinux context with (instructs selinux to perform full relabel on next
reboot):
`touch /.autorelabel`
Fix bootloader config issues
(kernel not found or similar error) Right Ans - edit boot config
confirm boot config is correct and make changes (spelling errors, etc)
add `systemd.unit=rescue.target` to the end of the linux16 line
regenerate grub config with the following command:
`grub2-mkconfig -o /boot/grub2/grub.cfg`
To diagnose boot issues more easily, you decide to disable 'quiet boot' and
'graphical boot' by removing 'quiet' and 'rhgb' from the kernel boot
parameters. How would you accomplish this so it's persistent? Right Ans -
Edit the 'GRUB_CMDLINE_LINUX' line in '/etc/default/grub' then regenerate
the bootloader config using 'grub2-mkconfig -o /boot/grub2/grub.cfg'.
Under normal circumstances, what is systemd's PID (Process ID)? Right
Ans - PID 1 - because it's the very first binary called by the kernel at boot, and
is responsible for starting up all other processes.
Which rescue parameter would you pass to the kernel from the grub2 menu if
your system was failing to boot because a filesystem check was failing?
Right Ans - systemd.unit=emergency.target
, Booting to the emergency target state drops to a rescue shell after the 'root'
filesystem has been mounted readonly, but BEFORE other FS checks are
carried out. Although you could do the same with 'rd.break' it would require
considerably more effort.
You are a member of a team of admins who are responsible for a critical
system. This system has two different web servers installed: The first (Nginx)
is used to serve content, the other (httpd) is installed only to satisfy
dependencies and should never be started as it causes a conflict. What
command could you run to ensure that 'httpd' is never accidentally started or
enabled by another admin? Right Ans - systemctl mask httpd
You're having a bad day and accidentally delete the 'initramfs' file in /boot
that matches your current kernel. Which command would you run to recover
from this? Right Ans - dracut
You've just made a configuration change to the 'SSHD' service and want to
daemon to reload it's configuration without disconnecting anyone. How could
you accomplish this? Right Ans - systemctl reload sshd.service
Persistent hostname change with systemd Right Ans - hostnamectl set-
hostname your.host.name
command to show open/listening ports Right Ans - ss -taupen
t = tcp
a = all types of connections (sending as well as listening)
u = udp
p = process ids (and information about the processes that are holding those
ports
e = extra information
n = numbers only (don't resolve the hostnames)
replacement for nslookup Right Ans - dig
replacement for traceroute Right Ans - tracepath
use mtr for real time updates (may need a yum install)
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