System Admin Questions

Q: - How are devices represented in UNIX?
All devices are represented by files called special files that are located in /dev directory.

Q: - What is 'inode'?
All UNIX files have its description stored in a structure called 'inode'. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as files and have an associated inode.

Q: - What are the process states in Unix?
As a process executes it changes state according to its circumstances. Unix processes have the following states:

Running : The process is either running or it is ready to run .
Waiting : The process is waiting for an event or for a resource.
Stopped : The process has been stopped, usually by receiving a signal.
Zombie : The process is dead but have not been removed from the process table.

Q: - What command should you use to check the number of files and disk space used and each user's defined quotas?
 repquota

Q: - What command is used to remove the password assigned to a group?
gpasswd –r

Q: - What can you type at a command line to determine which shell you are using?
echo $SHELL

Q: - Write a command to find all of the files which have been accessed within the last 30 days.
find / -type f -atime -30 > filename.txt

Q: - What is a zombie?
Zombie is a process state when the child dies before the parent process. In this case the structural information of the process is still in the process table.

Q: - What daemon is responsible for tracking events on your system?
syslogd

Q: - What do you mean a File System?
File System is a method to store and organize files and directories on disk. A file system can have different formats called file system types. These formats determine how the information is stored as files and directories.

Q: - What does /boot directory contains?
The /boot/ directory contains static files required to boot the system, such as the Linux kernel, boot loader configuration files. These files are essential for the system to boot properly.

Q: - If some one deletes /boot directory from your server, than what will happen?
In that case your server will be in unbootable state. Your Server can’t boot without /boot directory because this directory contains all bootable files

Q: - What does /dev directory contain?
The /dev directory contains all device files that are attached to system or virtual device files that are provided by the kernel.

Q: - What is the role of udev daemon?
The udev demon used to create and remove all these device nodes or files in /dev/ directory.

Q: - What kind of files or nodes /dev/ directory contains and how do I access or see device files?
Block Device Files:-

Block device files talks to devices block by block [1 block at a time (1 block = 512 bytes to 32KB)].
Examples: - USB disk, CDROM, Hard Disk
# ls /dev/sd*

brw-rw----	1 root	root	8,	0 Mar 15  2009 sda
brw-rw----	1 root	root	8,	1 Mar 15  2009 sda1
brw-rw----	1 root	root	8,	2 Mar 15  2009 sda2
brw-rw----	1 root	root	8,	3 Mar 15  2009 sda3
brw-rw----	1 root	root	8,	4 Mar 15  2009 sda4
brw-rw----	1 root	root	8,	16 Mar 15  2009 sdb

Character Device Files:-
Character device files talk to devices character by character.
Examples: - Virtual terminals, terminals, serial modems, random numbers
#ls /dev/tty*

crw-rw----	1 root	root	4,	64 Mar 15  2009 ttyS0
crw-rw----	1 root	root	4,	65 Mar 15  2009 ttyS1
crw-rw----	1 root	root	4,	66 Mar 15  2009 ttyS2
crw-rw----	1 root	root	4,	67 Mar 15  2009 ttyS3

Q: - Tell me the name of device file for PS/2 mouse connection.
/dev/psaux

Q: - Tell me the name of device file for parallel port (Printers).
/dev/lp0

Q: - What does /etc/X11/ directory contains?
The /etc/X11/ directory is for X Window System configuration files, such as xorg.conf.

Q: - What does /etc/skell directory contains?
The /etc/skel directory contains files and directories that are automatically copied over to a new user's home directory when such user is created by the useradd or adduser command. 

Q: - Rembember some Port no?

samba                                     139                  

samba-swat                             901

ftp                                           20 & 21

ssh                                           22

telnet                                       23

nfs                                           2049   

dns                                          53

squid                                       3128   

http                                          80

https                                        443

pop3                                        110

smtp                                        25

For more Questions Click here