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TR1 > General > Flashcards

General Flashcards

1
Q

Do you know the basic differences between Red Hat and CentOS?

A

Centos is free but is community supported, while redhat isn’t free but has support (for troubleshooting) provided by paid vendors. Centos for individual personal use, redhat for corporate use.

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2
Q

Why would you prefer Linux over Windows or any other operating system?

A

Linux is open source,
secure, multitasking, light weight, provides more uptime, less vendor dependency.

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3
Q

Which RHEL versions are you familiar with?

A

RHEL 7, 8, 9

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4
Q

Which ticketing system are you familiar with?

A

Jira

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5
Q

What is the structure of Linux, or what are the core components of the Linux OS?

A

The structure of Linux, or the core components of the Linux OS, typically includes:
Kernel: The core of the operating system that interacts with the hardware and manages system resources.
Shell: The interface that allows users to interact with the operating system through command-line commands or scripts.
Filesystem: The hierarchy of directories and files that store data and programs. Libraries: Collections of precompiled functions and routines that applications can use.
Utilities: Various command-line and GUI tools for managing the system and performing tasks.
Processes: Running instances of programs or commands that perform tasks.

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6
Q

What is the difference between shell and Kernel?

A

shell is the interface between the user and the
kernel.

kernel is an interface between the shell and hardware.

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7
Q

Which commands do you use on a routine basis?

A

uname, ifconfig, lsblk, du, df, hostname, w, who,
uptime, top, ps, nmcli

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8
Q

How can we check the hostname?

A

hostname, hostnamectl

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9
Q

What is the command to check the OS release?

A

cat /etc/os-release, cat /etc/redhat-release

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10
Q

How can you find out the kernel version of a Linux system?

A

uname -r

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11
Q

What is the difference between “su” and “su -“?

A

su: switch users to a new user by adding a shell, while keeping the environment (home directory for example) of the PREVIOUS user.

su -: switch users to a new user by adding a shell, while maintaining the environment (home directory for example) of the NEW user.

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12
Q

Which command do we use to get the commands you executed recently?

A

history and up arrow

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13
Q

What are binaries, and where are they stored?

A

Binaries are executable files written in binary code.
They are stored in /bin for the regular user, and system binaries are stored in /sbin.

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14
Q

What is the purpose of the /boot and /etc directories?

A

/boot – booting files
/etc – configuration
files

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15
Q

What does the /proc file system contain, and what is the size of this file system?

A

virtual file system
with 0 byte size. contains the kernel related files. it does not take space from the disk.

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16
Q

What is the basic difference between the /bin and /sbin directories?

A

/bin stores user binaries

/sbin stores system binaries

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17
Q

Which file system contains system configuration files?

A

/etc

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18
Q

What is the path to the directory that contains environmental files?

A

/etc/skel

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19
Q

Do you know how to execute multiple commands in a terminal?

A

; semicolon to separate commands and execute them in one go. -exec with find

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20
Q

Where are system binaries kept?

A

/sbin

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21
Q

What does the /opt directory/file system contain?

A

contains the optional or third party tools

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22
Q

What information can we extract from the uptime command?

A

current time of the system, how long system is up, no. of users logged in, load average at 1, 5 and 15 minutes.

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23
Q

What is the command to list all logged-in users and the time the server has been up for?

A

w, who

w
command is more organized and gives more information

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24
Q

What types of different timings are kept in record by Linux for files and directories, and which command would exhibit that information?

A

stat <filename> gives the
access (last time file was opened)
modify (change contents)
change (change metadata)</filename>

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25
Q

What is the pwd command used for?

A

present working directory, helps navigatae where you are
in the system

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26
Q

What is the difference between / and /root?

A

/ is the root filesystem, biggest.
/root is the home directory of root user

27
Q

How can we create a directory?

A

mkdir directory-name

28
Q

What does directory structure mean?

A

In computing, the way the operating system arranges files and directories

29
Q

How to create a directory structure /dev/app/apache?

A

mkdir -p /dev/app/apache

30
Q

What does the -p flag mean in mkdir?

A

-p flag provides or creates the directory structure. parent

31
Q

How can you list the directory tree structure?

A

tree command.
tree directory-name

32
Q

How can we update the time stamp of an existing file?

A

touch file-name

33
Q

How can we long list files and sort by time stamp?

A

ls -lt

34
Q

How can we recursively show the contents of the directory and sub- directory in the form of long list?

A

ls -lR

35
Q

Difference between “>” and echo “»” sign.

A

> will overwrite if the contents are already there

> > will append the contents.

36
Q

What is the difference between appending to a file Vs overriding a file, and how would you do that?

A

existing contents will still be in file, new contents will be added
overwrite the existing contents.

37
Q

Let’ say /var is 95% utilized, how would you know which files/dir(s) are consuming the most space under /var?

A

du -h /var | sort -rh | head

38
Q

How would you nullify/truncate the contents without deleting the file?

A

echo > filename or
> filename

39
Q

For a given directory structure “/tmp/users/data” you are required to delete the Users directory and everything underneath it (recursively without getting prompted).

A

rm -rf /tmp/users

40
Q

What is metadata? Where is metadata of a file or directory stored?

A

Metadata is data about data, such as information about a file or directory (permissions, ownership, timestamps (atime, mtime, ctime), size, and file type)

It’s stored within the inode (index node) associated with each file or directory

41
Q

How to list the metadata of a file or directory?

A

stat file or directory name

42
Q

How to find out the free inode numbers on /boot file system?

A

df -ih /boot

43
Q

How to know the type of a file whether if it is a file, directory or archive?

A

file file name

44
Q

How can we copy a file or directory while preserving the time stamp?

A

cp -p file or directory name

45
Q

How to read 2 different files and redirect the output into one larger file?

A

cat file1 file2&raquo_space; file3

46
Q

What is the head command? How many lines does it show by default?

A

it reads the file from the top and by default prints the first ten lines

47
Q

What is tail command? How many lines does tail command show by default?

A

it reads the file from
the bottom and by default prints the last ten lines

48
Q

What is the difference between “/var/log/secure” and “/var/log/messages”?

A

security and authentication logs
system error related logs

49
Q

What is the path to the system error logs?

A

var/log/messages

50
Q

What information /var/log/dmesg or command dmesg contain?

A

hardware related logs, info about
hardware. boot related logs as well

51
Q

How do you list the block devices?

A

lsblk

52
Q

What are the slowest and fastest components of the system?

A

hard disk is slowest, cpu is fastest

53
Q

Why do we need RAM if we have the hard disk for storage?

A

a very essential and critical component provides fast and temporary storage since hd cannot match the speed of the cpu, compliments the
disk

54
Q

When RAM gets full where does data go?

A

swap space

55
Q

How can we get the Swap space available in system?

A

free -h, swapon –show

55
Q

What is swap space and where does it resides?

A

virtual memory on the hard drive

56
Q

What is the purpose of df command?

A

report the filesystem disk usage space. whole system. system
wide disk utilization

57
Q

How would you make df command human readable?

A

df -h

58
Q

What is the purpose of du command?

A

disk usage or utilization of particular directory or filesystem

59
Q

How can we get the disk utilization of a /tmp directory?

A

du -sh /tmp

60
Q

How can you know that user is allowed to write in the file or not?

A

ls -l file will give the permissions.
stat

61
Q

List the last 15 messages from the file which contains authentication/security logs?

A

tail -15
/var/log/secure

62
Q

How can we get the real time updates in /var/log/secure file?

A

tail -f /var/log/secure

TR1 (8 decks)

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