4 File Management & 10 Network Settings Flashcards by Leondro Simental

/bin

stores essential command-line utilities and binaries

e.x. ls

How well did you know this?

Not at all

Perfectly

/boot

stores files to boot system

How well did you know this?

Not at all

Perfectly

/dev

stores hardware and software device drivers

e.x. storages devices here

How well did you know this?

Not at all

Perfectly

/etc

stores basic config files for system and services

e.x.
/etc/samba/smb.conf file stores Samba config data
-manage SSH access
-firewall rules
-software management settings

How well did you know this?

Not at all

Perfectly

/home

stores users’ home dir and their personal files

How well did you know this?

Not at all

Perfectly

/lib

stores shared program libraries required by the kernel, CLI utilities and binaries

How well did you know this?

Not at all

Perfectly

/media

stores mount points for removable media like CD-ROMS and floppy disks

How well did you know this?

Not at all

Perfectly

/mnt

mount point for temporarily mounting file systems

How well did you know this?

Not at all

Perfectly

/opt

stores optional files of large software packages.
often packages create sub directories

e.x. /opt/nessus contains files for Nessus vulnerability scanning programs

How well did you know this?

Not at all

Perfectly

/proc

virtual file system representing continuously updates kernel info in a user file

e.x. /proc/mounts

How well did you know this?

Not at all

Perfectly

/sbin

Stores binaries used for boot process and by the root user

e.x. /sbin/ifconfig used to manage network interfaces

How well did you know this?

Not at all

Perfectly

/sys

a VFS storing info about devices

e.x. /sys/block includes links to devices that are stored in various subdir under /sys/ devices/

How well did you know this?

Not at all

Perfectly

/tmp

stores temporary files that may be lost on system shutdown

How well did you know this?

Not at all

Perfectly

/usr

contains important subdir

How well did you know this?

Not at all

Perfectly

/usr/bin

/usr/bin - .exe programs that can be used by all users

How well did you know this?

Not at all

Perfectly

/usr/local

/usr/local - custom built applications stored here by default

How well did you know this?

Not at all

Perfectly

/usr/lib

/usr/lib - objects libraries and internal binaries needed by .exe files

How well did you know this?

Not at all

Perfectly

/usr/lib64

/usr/lib64 - same purpose as /usr/lib but meant for b4-bit systems

How well did you know this?

Not at all

Perfectly

/usr/share

/usr/share - contains read-only architecture independent files. can be shared among different architectures of an OS

How well did you know this?

Not at all

Perfectly

/var

stores variable files that are expected to change constantly

e.x. log files, printer spools, and some networking services

How well did you know this?

Not at all

Perfectly

stat command

displays file metadata

How well did you know this?

Not at all

Perfectly

file command

displays info on the file type and application compatibility

e.x.
.pdf version info
.jpeg image info

How well did you know this?

Not at all

Perfectly

absolute path

defines dir to traverse, starting from root of file system “/”

How well did you know this?

Not at all

Perfectly

relative path

defines path beginning from the users current location instead of “/”

How well did you know this?

Not at all

Perfectly

index node (inode)

the object identifier that stores metadata of a file and is represented as an integer
Inode tables map the inode value to corresponding file/dir

e.x. perms, time-stamps, ownerships, block locations, etc.

How well did you know this?

Not at all

Perfectly

ln –backup -f -s -i -v

link to a target file/dir
–backup backup existing destination files
-f Remove existing destination files
-s symbolic link
-i prompt to remove destination files
-v print name of file before linking

links can be made for file and dir, but cannot link a target dir to a destination dir, nor can the link exist between file systems (e.g. ext4 to ext3)

ln [options] {target name} {link name}

links are seen in ls -l and point to the target file its linked to.

How well did you know this?

Not at all

Perfectly

difference between hard and symbolic links

hard links - are treated as a file and link to the same in as its target file, if the target file is deleted, the hard link still exists.

symbolic links - create their own inode # that link to the target file, if the target file is deleted, the link is broken; however, the link can be unbroken if the same file and extension the link targeted is recreated

How well did you know this?

Not at all

Perfectly

”.” “..”

. - current dir
.. - previous dir

How well did you know this?

Not at all

Perfectly

tree command -a -d -s -D

display file system in familial structure

-a all files including hidden
-d dir only
-s display file size
-D display last modification date

How well did you know this?

Not at all

Perfectly

ls -a -l -d -R -s

list files:
-a all contents including hidden
-l in long format
-d dir only
-R contents of subdir
-s display file sizes

How well did you know this?

Not at all

Perfectly

rm -f -i -R

-f never prompt confirmation
-i interactive mode prompting for confirmation (usually set as an alias)
-R recursively remove a non empty dir and its contents

How well did you know this?

Not at all

Perfectly

difference with rm and rmdir

rmdir specifies dir and only removes the dir; the contents are then placed in the location its parent dir originally existed

How well did you know this?

Not at all

Perfectly

head/tail -n

specify number of lines with a space and #

How well did you know this?

Not at all

Perfectly

tee command

command [options] [arguments] | tee [options] {file names}

reads the input and both prints and sends (think of it as redirects) output to each specified file

-a appends

How well did you know this?

Not at all

Perfectly

xargs command definition and process

command [options] [arguments] | xargs [options] {command}

used after pipe and executes a command for each argument in the previous command with a relation to the results and a space present

e.x. find /projects -type f -name “*.pdf” | xargs rm

finds files in projects with the .pdf extension and xargs runs rm for each file as its own instance

How well did you know this?

Not at all

Perfectly

xargs options -I( uppercase i)
-L -p n -E -t -s

-I {replacement string}

Consider each line in the standard input as a single argument

-L {number of lines}

Read a specified number of lines from the standard input, and concatenate them into one long string

-p

Prompt the user before each command

-n {number of arguments}

Control the number of argument read at a time from scource input

-E {end of string}

Represent the end of the standard input

-t

Preview output before executing

-s {max size}

Set the maximum allowable size of an argument list to a specified number of characters

How well did you know this?

Not at all

Perfectly

find format and options

find {where to search using path} {option} {search criteria}

options
-name
-type f/d
-perm
-user
-group

only searches the files system not the contents of a file
should print absolute path to file

How well did you know this?

Not at all

Perfectly

locate command

searches like find but relies on index database and is quicker and uses files and dir along a path but requires up-to-date database

locate [options] {string}
option -i ignore case

updatedb command

build and update database of files based on /etc/update.conf

/etc/update.conf

/var/lib/mlocate/mlocate.db

.conf can be changed and set to exclude dir for indexing. (link?)

/var is where the db is located.

which command

displays path of a specified command

printf command

like echo but allows more control using “\n”

”" indicates format characters like newline

tr command

translate a string replacing {character1} with {character2}

wc command -c -m -l -w

word count command

-c byte count
-m character count
-l newline count
-w work count

sort command -k{column #} -n - r -t{delimiter}

arrange lines in file:

-k{column #} specify field values from 1+
does -k1..3 work?
-n compare sort lines to numerical value
-r sort filed in descending value
-t{delimiter} separate on field from another

cut command -c -d{delimiter} -f{files #} -s

extract specified lines of a file
-c specify the character # to start each cut
-d{delimiter} separate one field from another
-s suppress line if delimiter not found

paste command

paste [option] {file names}

merges files where each line of a file represent a column or each line is pasted parallel to with respect to the same line of the other file

default delimiter separates fields with a tab
-d {delimiter}

diff command -b -i -t -w -c -u

compares file1 to 2:
< before a line means file 2 is missing the line and could be removed to match
> before a line means file 1 is missing line found in file 2 and could be added to match

-b ignore spacing diff
-i ignore case diff
-t expand tab characters in output
-w ignore spacing diff
-c display diff with 3 lines of context
-u out in unified mode more streamlined

awk command def and operations

awk [options] [‘patterns {actions}’] {file-names}

performs pattern matching on files.
The command is followed by a pattern and a action to be performed in single quotes.
If no pattern specified, action is performed on all input data input.
If no action is specified, the line with the pattern is printed.

awk examples

query and retrieve all records beginning with “a” “b” or “c” :
awk ‘/[abc]/’ example.txt

’/{pattern}/’ matches address in sed that can match to every occurrence if specified

[] implies separately?

retrieve record whose 1st field begins “abc” :
awk “abc” example.txt

sed command [options]: d, “-n,p”, s “s,g”

sed {‘option/address/ action’} {file-names}

stream editor cmd to modify text files

d- delete lines matching specified pattern or line
-format end /#d or alone in single quotes line=# or x,yd range
-n,p - print only lines containing pattern
- s - substitute first occurrence of string
-s formates as ‘s/pattern/substitute/‘
Adding a # at the end “/“ specifies after
the # of occurrences, substitute once in with #g its every time the occurrence is met
- s,g - globally substitute original string with replacement for each occurrence
-formates with ‘s/pattern/substitute/g’

-address specifies lines to act on or text matching given regular expression pattern
-optional
-action is name of input file l
-e.x. cut?

option/address/action enclosed in single quotes

Other formats
Add parenthesis after first letter of each word:
echo “Welcome To The Geek Stuff” | sed ‘s/(\b[A-Z])/(\1)/g’
Replace string on line number:
$sed ‘3 s/unix/linux/’ geekfile.txt
Print replace line twice: with /p flag
sed ‘s/unix/linux/p’ geekfile.txt

IP [subcmds]: l , a , r, n

link (l)- display and modify network interfaces
address (a) - display and modify IP addresses
route (r) - display and alter routing table
neigh (n) - display and manipulate neighbor objects (ARP table)

must be done w/ sudo

modifying IP addr

Ip addr {show} {add| del} {Address/cidr} dev {interface name}

ip -4/6 addr to show only ipv4/6

modify network interfaces

Ip link {show} {set| add| del} dev {exit interface} {up|down}

alter routing table

Ip route {list} {add| del} {network id/cidr} {via| dev} {IP addr|exit interface}

default route
ip route add default via {ip addr} dev {exit interface}

route cmd

can also add a route with :
route {add| del} -net {net ID/CIDR} netmask {subnet mask} dev {interface}

ifconfig ip addr assign

ifconfig [interface-name] [ip-address] netmask [subnet-mask]

secondary ip addr:
ifconfig [interface-name]:0 [ip-address] netmask [subnet-mask]

ifconfig enable or disable interface

ifoncifg {interface} {up| down}

if config change mac addr

ifconfig {interface} hw ether {mac-addr (“:” delimiter)}

ifcfg command

ip and ifconfig alternate but lest robust

iwconfig command nick, mode, freq, channel, retry

wireless NIC configs

nick {name} - set nickname for NIC

mode {mode}- set operating mode corresponding to topology

freq {#} - set Wi-Fi frequency

channel {#} - set Wi-Fi channel

retry {#} set max # MAC retransmission for NIC

nmcli [subcmds]

most fundamental tool for NetworkManager interfaces

general status -view summary of network connectivity

connection show - view id info for each NIC

con {up| down} {dev ID} - {enable| disable} specified NIC

con edit {dev ID} - interactive mode to configure NIC

device status - display current status of NIC

nmtui cmd

text based user interface to configure network options

GNOME Network Manager applet

networkmanager GUI tool on GNOME desktop

where are network config stored?

in many files and dir
found in /etc/sysconfig or /etc/network for many Debian derivatives

what is /etc/sysconfig/network file

configures hostname, and gateway info, and if networking should enable at boot

what is /etc/sysconfig/network-scripts dir

config files for NICS, bonds, bridges in the form of ifcfg-<NIC> as a per interface basis</NIC>

e.x.
static or dynamic IP
enables or disabled
etc.

previous tools better manage files than editing file directly

ethtool cmd -S -i -t -s -f

manages NIC driver and network configs:

-S {interface} - show stats for NIC
-i {interface} - show driver info on NIC
t {interface} - execute self-test on NIC
-s {interface} {settings} {value} - change some NIC settings such as speed and duplex mode
-f {interface} - write (“flash”) a firmware image to NIC

where is primary DHCP client config file

/etc/dhcp/dhclient.conf file

enabling configeration of DHCP client settings, including timeout values, dynamic DNS configs, etc.

file is called and managed by NetworkManager

dhclient cmd

manages current config:

alone send broadcast DHCPDiscover

-r release current IP config

how is DNS managed

in /etc/host file or via DNS server

hostnamectl cmd

view system hostname

set hostname with hostnamectl set-hostname {hostname}

what is /etc/host file

system file recording association of IP addr to hostnames in that order

e.x. connecting to experimental server no registered on network

what is /etc/resolv.conf file?

file recording DNS server entries in newlines as server-hostnames and their IP addr in that order

maintain order for new self made entries

what is /etc/nsswitch.conf file?

specifies the order to resolve hostnames and ips

format:
host: (tab) {1st} {2nd} {myhostname}

ex:
hosts: (tab) /etc/hosts dns myhostname

ssh files

/etc/ssh/ssh_config : defining client settings usually not custumized

/etc/ssh/sshd_config “ contains many config options (mostly security oriented)
e.x.
Port 2222
block root authenticating over ssh:
PermitRootLogin no

key-based auth preventing passwd authentication:
PublicKeyAuthentication yes : set 1st then test
PasswordAuthentication no : 2nd

changes made must restart sshd

what is ~/.ssh/config ?

configure user specific setting for the SSH connections and can include many

prevent remembering setting of multiple server connections

e.x.
HOST {hostname}
(tab) Hostname {FQDN}
(tab) User {uname}
(tab) port {port}

what is ~/.ssh/authorized_keys ?

stores keys on the remote SSH servers the client connects to for key based authentication

file on the remote server not host

what is ~/.ssh/known_hosts ?

file that stores public keys of remote systems client connected to. located local SSH client to protect from man-in-middle

how to configure key based authentication?

on client machine:
Generate key pair
1. ssh-keygen

Transfer key to remote system
2. ssh-copy-id {username}@{ip-addr of remote host}

Test connection
3. ssh {username}@{ip-addr or remote host}

SSH port forwarding

tunneling an application through SSH

e.x. VNC on port 5900

SCP tool and cmd

copy data to or from remote server over SSH. uses TCP:22 by default

scp {file name} {username}@{ip-addr of remote host}:/home/dir

sftp cmd

SSH FTP uses SSH tunnel

sftp {username}@{ip-addr of remote host}:{file}

rsync cmd

over SSH or rsyncd daemon

copies files both ways but only the differences between the same file: synchronizing

synchronize from one location to another:
rsync -a /home/mydir/ {username}@{ip-addr or remote host}:/home/mydir/

remote GUI tools

cockpit : connect via : http://{IP-addr}:9090

VNC: Virtual Network Computing offering complete access to remote desktop w/ client-server model giving remote admin complete access

XRDP: Microsoft RDP protocol

X FORWARDING: X Windows System (X11) for Linux systems and is self aware. Can forward X traffic through SSH

iftop cmd

iftop [options] [-i {interface}]

display bandwidth usage

iperf cmd

test maximum throughput an interface will support

On the server run:
iperf -s
On the client run:
iperf -c {server address}

resolvectl cmd

resolvectl query {domain-name}

manually query name resolution services to confirm addresses and names are accurately
returned

dig cmd name

can test DNS by outputting ip-addr mapped to domain names, the DNS server that answered the query, and how long it took to receive answer

The command:
dig @{IP address} {domain name}

The basic syntax:
dig {domain name}

nslookup cmd

nslookup {domain name}

test name resolution

host cmd

gather info and testing name resolution and even against a DNS server using its ip-addr

The command:
host {domain name} {IP address}

The basic syntax:
host {domain name}

WHOIS cmd

name resolution protocol queries DNS servers to display hostname, FQDN, IP-addr, and other info

whois [options] {domain name}

clear ARP entry

arp -d {ip-addr}

pinging will re-enter entry to trouble shoot

arp -a views cache

Brainscape's Knowledge GenomeTM

4 File Management & 10 Network Settings Flashcards

Brainscape's Knowledge Genome^TM