System Fundamentals Flashcards by t t

System admin

root

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USed to determine sudo privileges

etc/sudoers

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sudoers drop in directory used to organize configurations

etc/sudoers.d

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open ssh daemon config file

etc/ssh/ssh_config

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Used to disable root logins

etc/ssh/ssh_config

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Used to edit suoders file

visuo

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provides a lock against simultaneous edits, provides basic sanity checks and checks for parse errors

visudo

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Allows a user to execute a command as the superuser or another user using -u

sudo

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allows users to run commands with a substitute user and group id

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what commands used with u will start the shell as a login shell with an environment similar to a real login shell

-l and -login

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What options run with sudo will execute an interactive shell if no command is specified

-i -login

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Collect report and save system activity info

sar

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provided by systat

sar

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creates a binary file for each day of the month

sa01

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Sar daily summary file format

sar01

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systat must be started in order for this command to run and collect data

sar

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Duration of sar collection can be changed in which file

etc/cron.d/systat

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option for sar to extract records from a file name

-f

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option for sar to report memory utilization

-r

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option for sar to report cpu utilization

-u

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report virtual memory statistics as well as stats on paging and block i/o

vmstatd

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Default start prints summary of usage statistics since last reboot

vmstat

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can run on an interval with a count or continuously

vmstat

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option for vmstat to display a table of memory stats

-s

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option for vmstat to report disk stats

-d

Display amount of free and used memory in the system

free

default kb

free

pulled from proc/meminfo file

free

option for free to display in human readbale format

-h

option for free to display in megabytes or gigabytes

-m -g

option for free to display in wide mode

-w

report file system disk space usage

reports amount of space available on file system of each file name given as an argument

If no argument is given this command reports the available space on all mounted file systems

option for df to list pseudo duplicate and inaccessible file systems

-a

Creates a file by converting groups of files and directories into an archive

tar

ends with tar extension followed by compression used

taro

option for tar to create an archive

-c

option for tar to extract an archive

-x

option for tar to specify the archive file name

-f

option for tar to filter through gzip

-Z

option for tar to filter through xz

option for tar to filter through bzip2

option for tar to show files processed by the command

used for copying and synchronizing files and directories both remotely and locally

rsync

option for rsync that uses archive mode which perserves permissions and ownership

-apti

on for rsync which uses verbose output

-v

option for rsync that compresses files during transfer

option for rsync that performs a backup during data synchronization

-b

option for rsync that performs a dry run

option for rsync that copies data recursively and does not keep ownership

option for rsync that skips files that are newer on the destination

an open source web server

apache http

provides content through the hypertext transfer protocol

apache http

apache http document root folder

vat/www/html

ports for http

443 80

An open source mail server from IBM

postflix

USes simple mail transfer protocol

postflix

postflix folder

var/log/maillog or mail.log

ports for postflix

25 465 587

how to enable and start a service?

systemctl enable -now

Synchronize the system clock on a linux system with a centralized ntp server

NTP

NTP ports

123/udp

More versatile then NTP

chrony

used to synchronize the sytem clock on a linux system but can be a server or a peer

chrony

log file categories

system service application event

Debian system log

var/log/syslog

Red Hat system logs

var/log/messages

A logging system developed by system

systemd journal

Stores data in binary format and can be viewed using journalctl utility

systemd journal

Option for systemd journal to view messages for a particular systemd unit

-u

Option for systemd journal to follow the journal for the latest messages

-F

Option for system d journal to jump to the end of the journal

-E

Option fo rsystemd journal to add explanatory texts

-X

Options for systemd journal to show entries froma specific data to another date

-s - u since until

A utility that can be installed and is by default often to manage logs

log rotate

make sure log files dont become too large and it dictates how they will be stored on a host

log rotate

main config file for log rotate

/etc/cron.daily

Provides a dynamically managed firewall that can support groups of rules called zones

firewalld

The command line client for firewalld

firewall-cmd

Predefined firewalld zones

public home drop block external internac dmz work trusted

This file tells you who can ssh into linux system

ssh_config

This keyword can be followed by usernames separated by spaces and login will only be allowed for them

allowusers

allowgroups

The initialization state that determines which system services should be running on a sys init system

runlevels

used to link a group of units together and describe a desired system state on a systemd system

target

Run level 0

poweroff target

Run level 1

rescue target (minimal environment with only essential services)

Run level 2,3,4

multi user target (normal system state)

Run level 5

graphical target includes gui

run level 6

reboot

systemctl list -units -t target

view active and loaded targets

systemctl get-default

returns the default target

systemctl isolate

start the unit specified on the command line and its dependencies and stop all others

An implementation of a flexible mandatory access control architecture in the linux OS that incorporates a set of kernel modifications and user space tools (it provides an extra layer of security by controlling and limiting what programs and uses can do) it works by assigning security labels to files processes, and other system objects and then defining rules to govern their interactions

selinux

Modes of SELinux Operation

Enforcing Permissive (logs policy violations but doesnt block them) Disabled

Security contexts for selinux

user role type range or level

System Fundamentals Flashcards

(97 cards)