Lesson 4 Flashcards
What makes enterprise distros of linux unique?
Much slower release cycles, older release of the linux kernel that are known to be stable.
What are some cons to enterprise linux distros?
They may lack support for the latest hardware
What are Redhat and Ubuntu’s support lifespane?
10 years
5 years
What are some BSD based OS’s
FreeBSD, NetBSD, OpenBSD
what is macOS based on?
BSD Unix with Bash shell
What command is used to find your kernel version?
uname -r
What do power supplies do?
They normalize power into standard voltage requirements. This allow hardware to be made that can be used anywhere in the world.
What does a motherboard do?
Normalizes the interconnection using standardized connectors and form factors to bring all the components of the computer together.
What type of software do motherboard sometimes have on board?
Firmware to deal with motherboard specific hardware
Give an example of a motherboard firmware
BIOS
What is the BIOS responsible for?
Configuration but also identifying, loading, and transferring control to the operating system
What standard did intel define motherboard standards?
EFI - extensible firmware interface
UEFI - Unified extensible firmware interface
What command can be used to see free memory?
free -m
What is the distinction between CPU and Processor?
A processor may hold more logic units than JUST the cpu, like a built in GPU for example
What command can you run to see information about your processor?
lscpu
What is the max size of memory that can be accessed on a 32 bit system?
4gb
What is HTT?
Hyper-Threading Technology Allows a single CPU to concurrently process multiple instructions thus virtually acting as multiple physical CPUs
What are modern connection standards for storage devices?
SATA or SCSI
What is partitioning?
Tells Linux if it should see the entire devices as one contiguous block of memory or if it is broken up into pieces
What would you expect the name of the device in /dev to be for the partition 3 of the third SATA drive?
sdc3
What does the lsblk -f command do?
Lists the drives and their partitions with the -f it also shows the file system format/type
Where are binary files stored?
/bin
/sbin
/usr/bin
/usr/local/bin
/usr/local/sbin
Where are configuration files stored?
/etc
What are some common files found in /etc
group
hostname
hosts
passwds
.conf files
profile
bash.bashrc
What are some common .config files in $HOME
.bashrc
.profile
.bash_history
Where is the kernel stored?
/boot
What is the PID that the kernel first runs after it’s loaded into memory?
1 or systemd
What is the /proc directory?
It’s a list of files and directories stored in memory, it’s not written to disk.
contains info about running processes, kernel config, system hardware
What is the /proc/sys directory?
Includes kernel configuration settings
What is the /dev directory?
Devices directory for all connected hardware devices
What is a block devices?
Devices where data is read or written
What is a character device?
Are those in which data is read and written in sequential order one character at a time (keyboards, text consoles, serial ports)
What is /dev/zero?
Provides as many null characters as requested from it
What is /dev/urandom?
Generates pseudo-random numbers
Explain the versioning in the following: vmlinuz-4.15.0-50-generic
4 = Kernel Version
15 = Major revision
0 = Minor revision
50 = Patch number
What command would you use to list all hard drives and partitions in /dev?
ls /dev/sd*
What does ps command do?
Lists the processes associated with the current shell
what does ps -uf do?
shows the relationship between parent and child processes
what does ps -v do?
Show the amount of memory usage associated with the current shell processes
what does uptime do?
Shows system uptime but also gives metrics on load averages
where are logs stored?
/var/log
what is the syslog daemon?
Manages system messages. it collects messages from services and programs and stores them in log files in /var/log
what does last do?
displays information about logins and reboots
what does logrotate do?
implements log rotation or cycling which means moving files, archiving/compressing, or emailing to sysadmin
what is the kernel ring buffer?
Fixed size data structure that records kernel boot messages as well as live kernel messages. It’s purpose is to log all kernel messages produced on boot
what is journald?
It is the standard logging component of the OS
what does journalctl utility do?
reads logs because they are in binary format
What virtual directory of /proc should you visit to see data that top is using?
/proc/887
What command is used to read /var/log/wtmp
last
What command is used to read /var/log/btmp
lastb
What command is used to read /run/log/journal/id/system.journal
journalctl
what does dmesg do?
prints the kernel ring buffer
What did systemd replace?
System V in all distros
What command to find out when last reboot was?
last
which hard disks are installed (kern.log)
less /var/log/kern.log
When last login occured (auth.log)
less /var/log/auth.log
what two command can you use to view the kernel ring buffer?
dmesg and journalctl -k
how can you use journalctl to query ssh?
journalctl -u ssh.service
In top, how can you kill a process?
by pressing k followed by the pid
What does the Link layer handle?
Communication directly between connected devices
What does the network layer handle?
Handles routing outside of individual networks with addressing (IP)
What does the application layer do?
Enables individual programs to talk to each other
What addressing is using on the Link Layer?
Mac
What does ip link show do?
Displays a list of all available network interfaces and their link layer addresses
What is CIDR notation?
Used to specify how many bits are set in the subnet mask
What are the private IP address schemas?
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
what does ip route show do?
shows the routes associated with link layers
What do routing tables do?
They hold a mapping of link layer mac addresses with IP addresses
How many groups do IPv6 addresses have?
8 groups of 4 hex digits
What are the three major prefix types in ipv6?
Global Unique Address
Unique Local Address
Link Local Address
What is the Neighbor Discovery Protocol?
Allows devices to find eachother and request information regarding a network they share
Where is DNS data stored?
/etc/resolv.conf
What is in the /etc/hosts file?
Checks to see if there is an address for a specific IP listed. It overrides DNS that may be at the Org or ISP level
what does the host command do?
Given a DNS name ig ives back IP address information
What does the dig command do?
Provides a more detailed version of host including DNS record types
What is a socket?
Communication endpoint for two programs talking to each other. Think web browser and web server
Name the three types of sockets
Unix socket
UDP
TCP
what does the ss command do?
Used to investigate all sockets
What commands would you use to assign IP addresses to an interface?
sudo ip addr add address dev interfacename
What does an entry in a host file look like?
ipaddress websitename
DNS Record type for textual data
TXT
DNS Type for reverse IP Address Lookup
PTR
DNS Type for a domain that has no address of its own and relies on another domain for this information
cname
DNS Type for a mail server
MX
What does bridging do?
Connects multiple network interfaces. Allowing all devices to communicate as if they were on the same link layer network
which ss command is used to see UDP sockets?
ss -u
