Ker.txt
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24. Theory
A. Explain Kernel in brief.
The kernel is the core component of the CentOS 7 operating system. It manages system resources, enables communication between hardware and software, and handles process scheduling, memory management, device management, and system calls. In CentOS 7, it is a Linux kernel (version 3.10 by default) designed for stability and long-term support.
B. Explain Shell and its types in brief.
The shell is a command-line interpreter that allows users to interact with the operating system. It takes user commands and passes them to the kernel for execution.
Common types of shells in CentOS 7 include:
- Bash (Bourne Again Shell): Default shell in CentOS.
- Sh (Bourne Shell): Original shell, basic scripting.
- Ksh (Korn Shell): More programming features.
- Csh (C Shell): C-like syntax, used in academic circles.
- Zsh (Z Shell): Advanced features and customization.
C. Explain about the Sudo command in brief.
`sudo` (superuser do) is used to execute commands with elevated privileges. In CentOS 7, it allows permitted users to run administrative tasks without logging in as root. Configuration is managed via the /etc/sudoers file.
Example: sudo yum install httpd
D. Explain Umask Value in detail.
`umask` stands for 'user file creation mode mask'. It determines default permission bits for newly created files and directories. In CentOS 7:
- Default umask is 0022:
- Files get 644 (rw-r--r--)
- Directories get 755 (rwxr-xr-x)
- It subtracts from the maximum permissions:
File: 666 - umask
Dir: 777 - umask
E. Explain in detail File system hierarchy and the all the directories in `/`.
CentOS 7 follows the Filesystem Hierarchy Standard (FHS):
- /: Root directory. Top of the hierarchy.
- /bin: Essential binary commands.
- /boot: Boot loader files (e.g., vmlinuz, grub).
- /dev: Device files.
- /etc: Configuration files.
- /home: Users’ home directories.
- /lib, /lib64: Shared libraries.
- /media, /mnt: Mount points for external storage.
- /opt: Optional software.
- /proc: Virtual filesystem with kernel info.
- /root: Home of root user.
- /run: Runtime information.
- /sbin: System binaries.
- /srv: Data for services.
- /sys: System and device info.
- /tmp: Temporary files.
- /usr: Secondary hierarchy, user applications.
- /var: Variable data like logs, mail, etc.
23. File Permission Task
Using Symbolic Method:
a. To File Fin in Ace folder:
• chmod u+w Ace/Fin
• chmod g=rw Ace/Fin
• chmod o-rwx Ace/Fin
b. To File Data in Ace folder:
• chmod u+rwx Ace/Data
• chmod g-r Ace/Data
• chmod o=x Ace/Data
c. To File Matrix in Ace folder:
• chmod a+wx Ace/Matrix
Using Numeric Method:
d. To File Log in Spade folder:
chmod 774 Spade/Log
e. To File Message in Spade folder:
chmod 640 Spade/Message
f. To File Error in Spade folder assign 761 and explain:
chmod 761 Spade/Error
761 = User: rwx (7), Group: rw (6), Others: x (1)
| 1 | 24. Theory |
| 2 | A. Explain Kernel in brief. |
| 3 | The kernel is the core component of the CentOS 7 operating system. It manages system resources, enables communication between hardware and software, and handles process scheduling, memory management, device management, and system calls. In CentOS 7, it is a Linux kernel (version 3.10 by default) designed for stability and long-term support. |
| 4 | B. Explain Shell and its types in brief. |
| 5 | The shell is a command-line interpreter that allows users to interact with the operating system. It takes user commands and passes them to the kernel for execution. |
| 6 | Common types of shells in CentOS 7 include: |
| 7 | - Bash (Bourne Again Shell): Default shell in CentOS. |
| 8 | - Sh (Bourne Shell): Original shell, basic scripting. |
| 9 | - Ksh (Korn Shell): More programming features. |
| 10 | - Csh (C Shell): C-like syntax, used in academic circles. |
| 11 | - Zsh (Z Shell): Advanced features and customization. |
| 12 | C. Explain about the Sudo command in brief. |
| 13 | `sudo` (superuser do) is used to execute commands with elevated privileges. In CentOS 7, it allows permitted users to run administrative tasks without logging in as root. Configuration is managed via the /etc/sudoers file. |
| 14 | Example: sudo yum install httpd |
| 15 | D. Explain Umask Value in detail. |
| 16 | `umask` stands for 'user file creation mode mask'. It determines default permission bits for newly created files and directories. In CentOS 7: |
| 17 | - Default umask is 0022: |
| 18 | - Files get 644 (rw-r--r--) |
| 19 | - Directories get 755 (rwxr-xr-x) |
| 20 | - It subtracts from the maximum permissions: |
| 21 | File: 666 - umask |
| 22 | Dir: 777 - umask |
| 23 | E. Explain in detail File system hierarchy and the all the directories in `/`. |
| 24 | CentOS 7 follows the Filesystem Hierarchy Standard (FHS): |
| 25 | - /: Root directory. Top of the hierarchy. |
| 26 | - /bin: Essential binary commands. |
| 27 | - /boot: Boot loader files (e.g., vmlinuz, grub). |
| 28 | - /dev: Device files. |
| 29 | - /etc: Configuration files. |
| 30 | - /home: Users’ home directories. |
| 31 | - /lib, /lib64: Shared libraries. |
| 32 | - /media, /mnt: Mount points for external storage. |
| 33 | - /opt: Optional software. |
| 34 | - /proc: Virtual filesystem with kernel info. |
| 35 | - /root: Home of root user. |
| 36 | - /run: Runtime information. |
| 37 | - /sbin: System binaries. |
| 38 | - /srv: Data for services. |
| 39 | - /sys: System and device info. |
| 40 | - /tmp: Temporary files. |
| 41 | - /usr: Secondary hierarchy, user applications. |
| 42 | - /var: Variable data like logs, mail, etc. |
| 43 | 23. File Permission Task |
| 44 | Using Symbolic Method: |
| 45 | a. To File Fin in Ace folder: |
| 46 | • chmod u+w Ace/Fin |
| 47 | • chmod g=rw Ace/Fin |
| 48 | • chmod o-rwx Ace/Fin |
| 49 | |
| 50 | b. To File Data in Ace folder: |
| 51 | • chmod u+rwx Ace/Data |
| 52 | • chmod g-r Ace/Data |
| 53 | • chmod o=x Ace/Data |
| 54 | |
| 55 | c. To File Matrix in Ace folder: |
| 56 | • chmod a+wx Ace/Matrix |
| 57 | Using Numeric Method: |
| 58 | d. To File Log in Spade folder: |
| 59 | chmod 774 Spade/Log |
| 60 | e. To File Message in Spade folder: |
| 61 | chmod 640 Spade/Message |
| 62 | f. To File Error in Spade folder assign 761 and explain: |
| 63 | chmod 761 Spade/Error |
| 64 | 761 = User: rwx (7), Group: rw (6), Others: x (1) |