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DAY 6

Notes

  • if permissions are not given to a user for a file the user can copy the file to another path and he will have all permissions to play with it
  • sticky-bit is default applied in tmp directory
  • dev directory is devices
  • etc is extended configuration
  • hard-disk should be purchased from same active region of service
  • hard - disk is purchased from EBS under Volume
  • Mailinator is a website where free email id is provided without credentials.
  • to make multiple directory at single time
mkdir -p A/B/D/H A/C/F A/B/E
  • By default mkdir make directory with permission 777 - umask(002)
  • By default text-files are given permission 662
  • + indicates ACL is being applied at some file
  • when we check ACL permissions on a file it shows a type mask which indicates highest permission on file In chmod we have a octal number system also there.
    Read - 4 Write - 2 execute - 1 remove - 0

754 4+2+1 = 7 read write execute 4+1 = 5 read execute 4 = 4 read

Sticky bit - 1 SGID - 2 2+1 =3 SGID and STicky bit 1 sticky 2 sgid

chmod 3777 /folder

Set File Access Control List -m stands for modify setfacl -m u:u4:rx /check u stands for user g stands for group

Get File Access Control List getfacl /check This is used to check the permissions

To remove facl we use setfacl -x u:u4 /check

umask is a factor in permissions which gives permission to every new file or directory.

To remove permission from firefox from user 4 setfacl -m u:u4:--- /usr/bin/firefox

LINUX Redhat

  • lsblk # shows partitions and hard disks in red Redhat
  • fdisk -l # shows partitions in present hard-disk
  • $ setfacl -b file.ext # Remove all ACL permissions
  • $ setfacl -x u:user-name file.ext # Remove single user ACL
  • $ yum provides package-name # it tells us which repo provides the specific package
  • $ yum reinstall package-name #reinstalls the specified package

Architecture (TASK)

  • Make two groups
  • in group 1 add 3 users
  • in group 2 add 5 users
  • create folders A to M as in pic
  • in K directory only permissions will be given to group 2
  • in L directory the permissions will be given to group 1
  • top 3 levels of architecture should not be touched by any of the groups
  • use stickybit and gsid
  • make the architecture using mkdir only once

File System Security

  • read = 4
  • write = 2
  • execute = 1
  • sticky bit = 1
  • SGID = 2
  • None = -
  • example 
    $ chmod 421 file.ext
# 421 == owner group other
  • all permission = 7
  • remove all permission = 000
  • add all permission = 777
  • read + execute = 4 + 1 = 5
 chmod  u     own     g     oth     
      special owner group   other

example $chmod 2777 /check # add SGID

User architecture

  • root - all permissions
  • group - name = Tech - has 2 users - all permission
  • other - has many users - no permissions
  • provide rx permission to single user in other * it can be done using ACL

Access control list

  • extended permission to be given to different users and permissions will be different
  • setfacl - > set file access control list
  • -m - > modify , user:user-name:permission
$ setfacl -m u:u4:rx file.extension
$ getfacl file.extension

  • to check ACL permission given to which user use getfacl

  • to remove ACL permission from a users

     $ setfacl -x u:u4 file.extension

  • Linux permissions is an important topic find out all questions related to it over google

  • UMASK - > changing permissions which comes by default

Storage Management

  • As per Student , storage is of 2 types ~ :
    1. Primary - > RAM
    2. Secondary - > HDD
  • By 2025 DNA will replace hard-disk to store data ( Project human as a storage device , 2kg DNA)
  • Why partitions are necessary : partitions are necessary to use same hard disk for multiple OS installations

Secondary Storage

There are two types of partition table

  • MBR (Master Boot Record)
  • GPT (Guided Partition Table)

Partition table is a memory or a storage which remembers no of partitions size and other info.

Partition table

* No of partitions that are possible to br created in a storage depends on partition table.
* It is of 2 types ~ :
  1. MBR
  2. GPT
* in a hard disk , how many partitions can be made beyond hard disk size
* MBR (Master Boot Record) - > minimum 4 partitions are possible approximately
* GPT - > around 10 partitions are possible approximately
* partition table is made inside the hard - disk itself
* MBR does not work over 2 TB data hard-disk
* GPT has no limit or around ( 8 ETB)
* By default GPT partition table is used Windows nowadays

MBR

* 64 byte size for partition information
* Parttions are of 2 types :
  1. Primary ( 4 partition possible)
  2. Logical
* OS is installed in Primary partition
* Stores data fast, secure, easy to access in primary partition
* other then primary partition , we can make extended partition
* extended partition does not store data but inside it we can creates logical partition (60 possible) which stores information.
* total partitions present = primary + logical in reality but it shows total partitions = primary + extended + Logical
* Only single extended partition possible with 3 primary partitions
* without extended , we can make 4 primary partitions.
* maximum 2TB hard-disk size

GPT

* GUID Partition table
* Globally Unique Identifier
* No logic regarding extended partitions
* 128 primary partitions are possible

UMASK

  • it defines the allotment of permissions to newly created files in linux.
  • to find current permissions to be given to file calculate umask value by 0777 - umask around
  • check with file system permissions numbering
  • other user has umask = 0002(default)
  • root user has umask = 0022 (default)

Primary Partition

  • An operating system needs primary partition for its installation.
  • We can make maximum 4 primary partitions in MBR.

Logical Partition

  • There are under Extended partition.
  • In an extened partition we have 60 Logical partition.

Python Class

impory sys
x= sys.argv[1:]
sum = 0
for i in x:
    sum = sum + int(i)
print(sum)
$python sum.py 1 5351 8453 465 3554 454 3
354015

TASK

  • open 4 ~ 5 processes and save data of RAM to hard-disk and after reboot re-transfer data from hard-disk to RAM
  • create a file that contains number of email ids,send a common email message to all emails and verify the email address as well
  • find number of devices connected from your hotspot using python
  • WAP to list number of users present in linux based OS
  • take 10 commands randomly from a user and check if it is present then run it other wise give voice based error message
  • make tree directory architecture and provide different permissions