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2021 Apple Interview

1 How does the PXE boot process work?

Dynamic Host Configuration Protocol

Using your DHCP server to store and serve this information looks like this:

  • The device sends out a DHCP broadcast and states that it needs to PXE boot
  • The DHCP server picks up this broadcast and replies with a suggested IP address to use.
    • If the server has the information on how to PXE boot, that information is included in its reply
  • The device then replies to the server and uses the provided address
  • Then the device contacts the PXE boot server (traditional a WDS server or SCCM server) and requests the boot file (also known as the Network Boot Program (NBP)) that it was told to look for from the DHCP server
  • The file is then loaded and launched on the client

2 Check Linux memory

/proc/meminfo

  • Free memory is the amount of memory which is currently not used for anything. This number should be small, because memory which is not used is simply wasted.

  • Available memory is the amount of memory which is available for allocation to a new process or to existing processes.

3 How do I add a DNS server via resolv.conf?

resolv.conf is the name of a computer file used in various operating systems to configure the system's Domain Name System resolver.

The /etc/resolv.conf file defines how the system uses DNS to resolve host names and IP addresses.

This file usually contains a line specifying the search domains and up to three lines that specify the IP addresses of DNS server. The following entries from /etc/resolv.conf configure two search domains and three DNS servers:

search us.mydomain.com mydomain.com
nameserver 192.168.154.3
nameserver 192.168.154.4
nameserver 10.216.106.3

If your system obtains its IP address from a DHCP server, it is usual for the system to configure the contents of this file with information also obtained using DHCP.