Linux server world
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This document contains 22 questions and answers related to Linux system administration. Some of the topics covered include the difference between processes and services, viewing cron status, logging client usage of server services, FTP access restrictions, Linux security tools, firewall basics, checking file system consistency, and scheduling cron jobs to run on a specific Saturday of the month.
![7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2
http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 2/10
Mail server – /var/log/mail/maillog [RedHat,centos]
ssh – /var/log/secure
Apache – /var/log/http/access.log
nfs – /var/lib/nfs/rmtab
4. How to FTP user access other directory except his own
home directory?
vim /etc/vsftpd/vsftpd.conf
Chroot_list_enable=yes
5. What are the Linuxbased security tools?
Selinux
Firewall
iptables
Tcpwrappers
6. What are the basic elements of firewall?
A firewall should be able to filter packets (drop/pass them) based
on certain rules specified by the user. The rules may be used to
identify an incoming packet to the computer or outgoing packet
from the computer, it can be based on target port number/ip add ,
traffic from a particular Network card etc…
The firewall rules can be in a tabular form (saved on the disk) from
where the firewall software can read them and implement it.
iptables firewall on Linux is a great example
7. What is a command to display top 10 users who are using
huge space?
du sh /home/* | sort r | head 10
8. How do find all failed login attempts via ssh?
tail f /var/log/secure | grep Failed
9. How do you configure Linux system as a router?
vim /etc/sysctl.conf
net.ipv4.ip_forward=1
systemconfignetwork
eth0 192.168.1.120 eth0:1 172.24.0.1
source
How to run shell
commands in python
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through python script
How to send an email with
attachment through Shell
script
How to install Nagios with
NRPE on Centos 6/RHEL
6
How to configure Nagios
on RHEL 6/CENTOS 6
from source
Linux Interview Questions
and Answers – Part 2
Linux Interview Questions
and Answers – Part I
What is a shell in
linux/unix ?
Python programming for
the absolute beginners
How to add new order
admin email notification on
Magento
ISCSI storage
management – A Storage
Area Network Protocol
MySQL performance
tuning with mysqltuner
perl script
How to flush postfix mail
queue and its various
operations
IPMI Interface – A
Intelligent Platform
Management Interface
Now Linux runs on
Windows Azure Platform
MySql basics for
beginners
SFTP Chroot Jailing –
Restricting users to their
individual home directories
How to split a file on linux
How to prevent users from](https://image.slidesharecdn.com/linuxserverworld-150702144546-lva1-app6891/85/Linux-server-world-2-320.jpg)
![7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2
http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 5/10
3.TCP gurantees that as long as you have a connection data sent
will arrive at the destination, UDP provides not guarantee delivery.
4.UDP is faster for sending small amounts of data since no
connection setup is required, the data can be sent in less time
then it takes for TCP to establish a connection.
18. What command do you run to check file system
consistency?
Need to run fsck [file system consistency check] command to
check file system consistency and repair a Linux / UNIX file
system.
fsck
19. What is the command to remove Lvm ,Pv and vg
1st remove the entry on /etc/fstab file & save – quit.
2nd remove LVM – lvremove lvname
3rd remove VG – vgremove vgname
4th remove PV – pvremove pvname
20. How to create SAMBA server in fedora 9 Linux?
yum install samba y
yum install sambaswat –y
vi /etc/samba/smb.conf
comment = windows sharing
path = path/your/share/directory
valid users = surendra
writable = yes
browseable = yes
then type testparm for code testing.
smbpasswd a username
smbpasswd e username
service smb restart
chkconfig smb on](https://image.slidesharecdn.com/linuxserverworld-150702144546-lva1-app6891/85/Linux-server-world-5-320.jpg)
Linux server world
- 1. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 1/10 Linux Interview Questions and Answers – Part 2 POST CATEGORY INTERVIEW Q&A, UNCATEGORIZED ∙ 2 COMMENTS 1. What is the difference between service and process? A process is any piece of software that is running on a computer. For example, your antivirus software runs in the background as a process, which was automatically started when the computer booted. Some processes start when your computer boots, others are started manually when needed. Some processes are services that publish methods to access them, so other programs can call them as needed. Printing services would be an example of a service type of process, where your email program can just call the print services process to say it wants to print, and the service does the actual work. 2. How to view crond status? If it’s show service is not found. Service crond restart 3. My clients are getting services from servers but how to know which client is using which service. is there any files to keep information about these? Clients used ftp, nis, samba, apache, squid, nfs and mail services how to know how many users got service from server side with date, time and client system ip? SUBSCRIBE FOR EMAIL Email Subscribe FIND US ON GOOGLE + Linux Server Wo + 159 Follow RECENT POSTS How to install apache httpd on ubuntu 11.04/ubuntu12.04 from LINUX INTERVIEW QUESTIONS AND ANSWERS – PART I HOW TO CONFIGURE NAGIOS ON RHEL 6/CENTOS 6 FROM SOURCE Find us on Facebook Linux Server World 3,482 people like Linux Server World Facebook social plugin Like
- 2. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 2/10 Mail server – /var/log/mail/maillog [RedHat,centos] ssh – /var/log/secure Apache – /var/log/http/access.log nfs – /var/lib/nfs/rmtab 4. How to FTP user access other directory except his own home directory? vim /etc/vsftpd/vsftpd.conf Chroot_list_enable=yes 5. What are the Linuxbased security tools? Selinux Firewall iptables Tcpwrappers 6. What are the basic elements of firewall? A firewall should be able to filter packets (drop/pass them) based on certain rules specified by the user. The rules may be used to identify an incoming packet to the computer or outgoing packet from the computer, it can be based on target port number/ip add , traffic from a particular Network card etc… The firewall rules can be in a tabular form (saved on the disk) from where the firewall software can read them and implement it. iptables firewall on Linux is a great example 7. What is a command to display top 10 users who are using huge space? du sh /home/* | sort r | head 10 8. How do find all failed login attempts via ssh? tail f /var/log/secure | grep Failed 9. How do you configure Linux system as a router? vim /etc/sysctl.conf net.ipv4.ip_forward=1 systemconfignetwork eth0 192.168.1.120 eth0:1 172.24.0.1 source How to run shell commands in python How to send an email through python script How to send an email with attachment through Shell script How to install Nagios with NRPE on Centos 6/RHEL 6 How to configure Nagios on RHEL 6/CENTOS 6 from source Linux Interview Questions and Answers – Part 2 Linux Interview Questions and Answers – Part I What is a shell in linux/unix ? Python programming for the absolute beginners How to add new order admin email notification on Magento ISCSI storage management – A Storage Area Network Protocol MySQL performance tuning with mysqltuner perl script How to flush postfix mail queue and its various operations IPMI Interface – A Intelligent Platform Management Interface Now Linux runs on Windows Azure Platform MySql basics for beginners SFTP Chroot Jailing – Restricting users to their individual home directories How to split a file on linux How to prevent users from
- 3. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 3/10 255.255.255.0 255.255.0.0 172.24.0.1 192.168.1.120 10. What is the UID and GID of root user? Can a normal user can change the ownership of a file? What is the command to change ownership of a file? The root UID/GID is 0 (zero). Which is why he can able to intervene in all normal users files even though he don’t had permission. A normal user will don’t have the permission to change ownership of file. The command to change ownership is < chown user.user file > 11. What is the diff b/w ext2 and ext3? Ext3 is a tiny bit slower than ext2 is, but it holds tremendous advantages. There is really only one difference between ext2 and ext3, and that is that ext3 uses a journal to prevent filesystem corruption in the case of an unclean shutdown (ie. before the filesystem is synced to disk). That makes ext3 a bit slower than ext2 since all metadata changes are written to the journal, and then flushed to disk, but on the other hand you don’t risk having the entire filesystem destroyed at power failure or if an unwitted person turns the computer off uncleanly. You don’t have to check the filesystem after an unclean shutdown either. Ext3 has three levels of journalling. Metadata (ie. internal filesystem structures) are always journalled, so that the filesystem itself is never corrupted. How ordinary data is written to the file system is controllable, though. The default option is the “ordered” mode, which causes file contents to be written to the filesystem before metadata is even committed to the journal. The highest reliable mode is called the “journal” mode, which causes file data to be committed to the journal before it is flushed to its final place, like the metadata. The least reliable mode, but rumoured to be the fastest, is called the “writeback” mode, which makes no promises at all regarding the consistency of file data. Only metadata is output reliably in writeback mode. So as for anything else, it’s mainly a matter of priority. If you don’t want ultimate speed, go with ext3. If you need the highest speed that is theoratically aquirable though, then go with ext2. For that to be effective you’ll probably need a really advanced hard drive controller, though. 12. As the system administrator you need to review Bob’s cronjobs. What command would you use? crontab –lu Bob changing their password on linux
- 4. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 4/10 13. What command is used to remove the password assigned to a group? gpasswd –r groupname 14. What are the different RAID levels? RAID level 0 RAID level RAID level 1 RAID level 2 RAID level 3 RAID level 4 RAID level 5 RAID level 6 RAID level 10 RAID level 50 15. How do you create a swapfile? dd if=/dev/zero of=/swapfile bs=1024 count=200M mkswap /swapfile swapon /swapfile 16. What does nslookup do? Nslookup is a program used to find information about internet Domain Name server. The two modes of nslookup are: Interactive and noninteractive. Using ‘interactive mode’ user can query the name servers for the information pertaining to hosts and domains. Using ‘noninteractive mode’ the user can just print the name and requested information of a host. 17. What is the difference between UDP and TCP? TCP is a Transmission Control Protocol. UDP is a User Datagram Protocol. There are four major differences between UDP and TCP: 1. TCP can establish a Connection and UDP cannot. 2. TCP provides a stream of unlimited length, UDP sends Small packets.
- 5. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 5/10 3.TCP gurantees that as long as you have a connection data sent will arrive at the destination, UDP provides not guarantee delivery. 4.UDP is faster for sending small amounts of data since no connection setup is required, the data can be sent in less time then it takes for TCP to establish a connection. 18. What command do you run to check file system consistency? Need to run fsck [file system consistency check] command to check file system consistency and repair a Linux / UNIX file system. fsck 19. What is the command to remove Lvm ,Pv and vg 1st remove the entry on /etc/fstab file & save – quit. 2nd remove LVM – lvremove lvname 3rd remove VG – vgremove vgname 4th remove PV – pvremove pvname 20. How to create SAMBA server in fedora 9 Linux? yum install samba y yum install sambaswat –y vi /etc/samba/smb.conf comment = windows sharing path = path/your/share/directory valid users = surendra writable = yes browseable = yes then type testparm for code testing. smbpasswd a username smbpasswd e username service smb restart chkconfig smb on
- 6. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 6/10 21. How to schedule cron backup to run on 4th Saturday of month? * * * * 6 weekdaynum 4 && sh /backup/test.sh 22. What is an inode? ext2 and ext3 file systems keep a list of the files they contain in a table called an inode table. The inode is referenced by its number. This is unique within a file system. The inode contains the metadata about files. Among the data stored in the inode is File type File permissions Link count User ID number of the file owner and the group ID number of the associated group Last modification time Location of the data on the hard disk Other metadata about the file ls li – view inode number only stat /etc/passwd – view inode details 23. How to see unallocated hard disk space on linux df h 24. How do u find remote machine operating system and version? nmap A –v 192.168.1.100 25. How do you port scanning with netstat command? netstat –an
- 7. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 7/10 26. Linux system monitoring Tools? top – Process Activity Command vmstat – System Activity, Hardware and System Information w – Find out Who Is Logged on And What They Are Doing Uptime – Tell How Long the System Has Been Running ps – Displays the Processes free – Memory Usage iostat – Average CPU Load, Disk Activity sar – Collect and Report System Activity mpstat – Multiprocessor Usage pmap – Process Memory Usage 27. Linux Network monitoring Tools? netstat and ss – Network Statistics iptraf – Realtime Network Statistics tcpdump – Detailed Network Traffic Analysis strace – System Calls /Proc file system – Various Kernel Statistics # cat /proc/cpuinfo # cat /proc/meminfo # cat /proc/zoneinfo # cat /proc/mounts Nagios – Server And Network Monitoring Cacti – Webbased Monitoring Tool Gnome System Monitor – Realtime Systems Reporting and Graphing 28. What is mean by system calls? A system call is the mechanism used by an application program to request service from the operating system. On Unixbased and POSIXbased systems, popular system calls are open, read, write, close, wait, exec, fork, exit, and kill. Many of today’s operating systems have hundreds of system calls. For example, Linux has 319 different system calls. FreeBSD has about the same (almost 330). Tools such as strace and truss report the system calls made by a running process. 29. Important port no:
- 8. 7/2/2015 Linux Server World | Linux Interview Questions and Answers – Part 2 http://linuxserverworld.com/linux-interview-questions-and-answers-part-2/ 8/10 SHARE → NFS – 2049 FTP – 21 SAMBA – 445 SSH – 22 DNS – 53 POP3 – 110 IMAP – 143 HTTPS – 443 HTTP – 80 30. How do u extract files from iso cd images in linux? mount –o loop disk1.iso /mnt/iso TAGGED WITH → answer • answers • interview • linux • question • questions 1 Tweet 0 2 Responses to Linux Interview Questions and Answers – Part 2 Sivakumar M says: February 19, 2014 at 8:45 AM Answer of 2nd question is # service crond status Firoj says: February 26, 2014 at 1:55 PM Got to knw new thngs.thanx a lot Leave a Reply 36Like Share REPLY REPLY