AIX Interview Questions and Answers

AIX is an operating system developed by IBM and is in fact Unix-based. It is typically used for enterprise servers and comes with a robust set of security options such as Kerberos V5 network authentication and dynamic secure tunnel authentication. AIX allows the system administrator to divide memory, CPU, and disk access between various jobs.It is mainly used for servers in large businesses where IT geeks get to work with it.

1.  What is the System Management Interface Tool (SMIT) ?

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SMIT is the System Management Interface Tool for AIX. It allows a user to navigate a menu hierarchy of commands, rather than using the command line. Invocation is typically achieved with the command smit. Experienced system administrators make use of the F6 function key which generates the command line that SMIT will invoke to complete the proposed task. SMIT also generates a log of commands that are performed in the smit.script file. The smit.script file automatically records the commands with the command flags and parameters used. The smit.script file can be used as an executable shell script to rerun system configuration tasks. SMIT also creates the smit.log file, which contains additional detailed information that can be used by programmers in extending the SMIT system.

2. What are the unique features of AIX ?

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The following are some unique system management features of AIX.

Logical Volume Manager :- The Logical Volume Manager (LVM) maintains the hierarchy of logical structures that manage disk storage.

System Resource Controller:- The System Resource Controller (SRC) provides a set of commands and subroutines for creating and controlling subsystems and is designed to minimize the need for human intervention in system processing.

Object Data Manager :- The Object Data Manager (ODM) is a data manager intended for the storage of system data.

Software Vital Product Data:- Certain information about software products and their installable options is maintained in the Software Vital Product Data (SWVPD) database.

Workload management :- Workload Manager (WLM) is designed to provide the system administrator with increased control over how the scheduler virtual memory manager (VMM) and the disk I/O subsystem allocate resources to processes. You can use WLM to prevent different classes of jobs from interfering with each other and to allocate resources based on the requirements of different groups of users.

Operating system updates:- The operating system package is divided into filesets, where each fileset contains a group of logically related customer deliverable files. Each fileset can be individually installed and updated.

3. What is VGDA?

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Volume Group Descriptor Area. It contains the information about volume group to which the physical volume belongs to. It also contains the information about physical partitions, logical partitions and logical volumes.

4. How do I know if my volume group is normal, big, or scalable?

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Run the lsvg command on the volume group and look at the value for MAX PVs. The value is 32 for normal, 128 for big and 1,024 for scalable volume group.

5. What does Logical Volume Manager(LVM) mean?

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The set of operating system commands, library subroutines and other tools that allow you to establish and control logical volume storage is called the Logical Volume Manager (LVM).

6. How do I create a volume group?

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Use the following command, where s partition_size sets the number of megabytes (MB) in each physical partition where the partition_size is expressed in units of MB from one through 1,024. (It’s one through 131,072 for AIX 5.3.)

The partition_size variable must be equal to a power of two (for example: one, two, four or eight). The default value for standard and big volume groups is the lowest value to remain within the limitation of 1,016 physical partitions per physical volume. The default value for scalable volume groups is the lowest value to accommodate 2,040 physical partitions per physical volume.

7. How can I change the characteristics of a volume group?

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The chvg command is used to change the characteristics of a volume group.

8. What is the login process to the AIX system?

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AIX is a multi-user system

9. When the user login he needs to provide the user name and password for authentication purposes.

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After the successful login, AIX starts the SHELL program

10. How do I create a logical volume?

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11. How do I increase the size of a logical volume?

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To increase the size of the logical volume represented by the lv05 directory by three logical partitions, for example, type extendlv lv05 3.

12. How do I display all logical volumes that are part of a volume group (e,g, rootvg)?

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You can display all logical volumes that are part of rootvg by typing the following command: #lsvg -l rootvg/

13. How do I list information about  logical volumes?

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Run the following command to display information about the logical volume #lv1: lslv lv1.

14. How can I clone the rootvg?

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You can run the alt_disk_copy command to copy the current rootvg to an alternate disk. The following example shows how to clone the rootvg to hdisk1: alt_disk_copy -d hdisk1.]

15. How do I replace a disk?

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16. How do I mirror a logical volume? 

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17. How can I display or set values for network parameters?

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The no command sets or displays current or next boot values for network tuning parameters

18. How do I get the IP address of my machine?

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Type one of the following: ifconfig -a or host Fully_Qualified_Host_Name. For example, host cyclop.austin.ibm.com.

19. How do I identify the network interfaces on my server?

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Either of the following two commands will display the network interfaces: lsdev -Cc if or ifconfig -a. To get information about one specific network interface, for example tr0, run the command ifconfig tr0.

20. What applications work with HACMP?

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All popular applications work with HACMP including DB2, Oracle, SAP, WebSphere, etc. HACMP provides Smart Assist agents to let you quickly and easily configure HACMP with specific applications. HACMP includes flexible configuration parameters that let you easily set it up for just about any application there is.

21. Can you explain the steps to mirroring rootvg in your environment?

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Mirroring “rootvg” protects the operating system from a disk failure. Mirroring “rootvg” requires a couple extra steps compared to other volume groups. The mirrored rootvg disk must be bootable *and* in the bootlist. Otherwise, if the primary disk fails, you’ll continue to run, but you won’t be able to reboot.

In brief, the procedure to mirror rootvg on hdisk0 to hdisk1 is

• Add hdisk1 to rootvg: extendvg rootvg hdisk1
• Mirror rootvg to hdisk1: mirrorvg rootvg hdisk1 (or smitty mirrorvg)
• Create boot images on hdisk1: bosboot -ad /dev/hdisk1
• Add hdisk1 to the bootlist:bootlist -m normal hdisk0 hdisk1
• Reboot to disable quorum checking on rootvg. The mirrorvg turns off quorum by default, but the system needs to be rebooted for it to take effect.

22. What is VPN and how it works?

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A VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together. Instead of using a dedicated, real-world connection such as leased line, a VPN uses “virtual” connections routed through the Internet from the company’s private network to the remote site or employee.

23. Can you describe SAN in your own words?

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A storage area network (SAN) is a high-speed special-purpose network (or subnetwork) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. Typically, a storage area network is part of the overall network of computing resources for an enterprise. A storage area network is usually clustered in close proximity to other computing resources such as IBM Power5 boxes but may also extend to remote locations for backup and archival storage, using wide area network carrier technologies such as ATM or SONET .

• A storage area network can use existing communication technology such as IBM’s optical fiber ESCON or it may use the newer Fibre Channel technology. Some SAN system integrators liken it to the common storage bus (flow of data) in a personal computer that is shared by different kinds of storage devices such as a hard disk or a CD-ROM player.
• SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network. SANs can incorporate subnetworks with network-attached storage (NAS) systems.

24. What is NAS?

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Network-attached storage (NAS) is hard disk storage that is set up with its own network address rather than being attached to the department computer that is serving applications to a network’s workstation users. By removing storage access and its management from the department server, both application programming and files can be served faster because they are not competing for the same processor resources. The network-attached storage device is attached to a local area network (typically, an Ethernet network) and assigned an IP address. File requests are mapped by the main server to the NAS file server.

• Network-attached storage consists of hard disk storage, including multi-disk RAID systems, and software for configuring and mapping file locations to the network-attached device. Network-attached storage can be a step toward and included as part of a more sophisticated storage system known as a storage area network (SAN).
• NAS software can usually handle a number of network protocols, including Microsoft’s Internetwork Packet Exchange and NetBEUI, Novell’s Netware Internetwork Packet Exchange, and Sun Microsystems’ Network File System. Configuration, including the setting of user access priorities, is usually possible using a Web browser.

25. What is SMTP and how it works?

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SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving e-mail. On Unix-based systems, sendmail is the most widely-used SMTP server for e-mail. A commercial package, Sendmail, includes a POP3 server. Microsoft Exchange includes an SMTP server and can also be set up to include POP3 support. SMTP usually is implemented to operate over Internet port 25. 

26. Do you have any idea about NAT?

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Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.

27. What is the purpose of NAT?

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NAT serves three main purposes:

• Provides a type of firewall by hiding internal IP addresses
• Enables a company to use more internal IP addresses. Since they’re used internally only, there’s no possibility of conflict with IP addresses used by other companies and organizations.
• Allows a company to combine multiple ISDN connections into a single Internet connection.        

28. Explain DHCP and its uses to an environment?

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• Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device’s IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.
• Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task. This means that a new computer can be added to a network without the hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP addressing for dial-up users.

29. What does SNMP stand for?

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Short for Simple Network Management Protocol, a set of protocols for managing complex networks. SNMP works by sending messages, called Protocol Data Units, to different parts of a network. SNMP-compliant devices, called Agents, store data about themselves in Management Information Bases and return this data to the SNMP requesters.

30. What do you know about TCPDump?

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TCPdump is a common computer network debugging tool that runs under the command line. It allows the user to intercept and display TCP/IP and other packets being transmitted or received over a network to which the computer is attached. Tcpdump works on most Unix-like platforms: Linux, Solaris, BSD, Mac OS X, HP-UX and AIX among others. On Windows, WinDump can be used; it’s a port of tcpdump to Windows. You must have a root or superuser authority to use TCPdump in a UNIX-like environment.    

31. How do I activate a network interface?

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To activate the network interface tr0, run the command ifconfig tr0 up.

32. How do I display routing tables, interface and protocol information?

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To display routing table information for an Internet interface, type netstat -r -f inet. To display interface information for an Internet interface, type netstat -i -f inet. To display statistics for each protocol, type netstat -s -f inet.

33. How will you create a file if a disk is given to you?

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34. Difference between JFS & JFS2?

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JFS:

JFS is a normal filesystem. We cannot create large files in JFS.

Files can be accessed dynamically.

Max file system size=1TB

Max file size=64GB

Inode size=128b

JFS2:

Can create a large size filesystems.

Files can be accessed accordingly as required. (not randomly or sequentially)

Max files system size=4PB

Max file size=4PB

Inode size=512

35. How will you find the inode number?

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How will you find LTG size?

36. Write the command format in AIX format.

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The command or process name should come first. The options should follow the command name, separated by a space, and preceded by a minus sign (-). Multiple options may be grouped immediately after a single minus sign or separated by spaces and each preceded by a minus sign

37. Write the date and calendar command.

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38. Write clear, echo, print and banner command.

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Clear: clears the terminal signal

echo : Writes what follows to the screen.

Banner : Writes character strings in large letters to the screen

39. Write the keyboard shortcuts used on AIX terminal.

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 Backspace : to correct mistakes.

•  <ctrl+c> : terminates the correct command and return to the shell.\
•  <ctrl+d> : end of transmission or end of file
•  <ctrl+s> : temporary stops the output to the screen
•  <ctrl+q> : resumes output which was stopped by ctrl+s
•   <ctrl+u> : erases the entire line.

40. Give the brief about man command.

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The man command will look in the on-line manual for information on the commands, subroutines and files with the name title. This information will be presented on the screen one page at a time for the user to browse.

The information consists of: 

PURPOSE : The title and a one-line description of the command

SYNTAX : The syntax of the command

DESCRIPTION : Many pages of information about the function and usage of the command with examples

FLAGS : Description of available options

FILES : Any system files associated with the command

RELATED INFO : The names of any related commands

BUGS : Any information about the behavior/performance of the command in unusual circumstances $ man <command for which you want the information> 

41. Explain the file types in AIX

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A file is a collection of data, stream of characters or a byte stream. No structure is imposed on the file by OS. The various file types are as follows:

• Ordinary (text or code data)
• Directory (table of contents, that stores a list of files within that directory)
• Special files(representing hardware or logical devices)

An ordinary file can contain either text or code data. Text files are readable by a user and can be displayed or printed. Code data, also known as a binary file is readable by the computer. Binary files may be executable. Directories contain information the system needs to access all types of files, but they do not contain the actual data. Each directory entry represents either a file or a subdirectory.Special files usually represent devices used by the system. 

42. How to configure a read/write optical drive?

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There are two methods for configuring a read/write optical drive. The read/write optical drive must be connected to the system and powered on.

Method 1:-Method one is the faster of the two methods. It only configures the read/write optical drive specified. To use this method, you must provide the following information:

• Subclass Defines how the drive is attached.
• Type Specifies the type of read/write optical drive.
• Parent Name Specifies the system attachment the drive is connected to.
• Where Connected Specifies the logical address of the drive.

Enter the following command to configure the read/write optical drive:

The following is an example of a read/write optical drive that has a SCSI ID of 6, a logical unit number of zero, and is connected to the third (scsi3) SCSI bus:

43. How to configure a read/write optical drive by using a configuration manager?

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Method of Configuration Manager, searching the current configuration, detecting any new devices, and automatically configuring the devices. This method is used when little information is known about the read/write optical drive.

• Use the configuration manager to configure all newly detected devices on the system (including the read/write optical drive) by typing: cfgmgr
• Type the following command to list the names, location codes, and types of all currently configured read/write optical drives: lsdev -C -c rw optical
• Determine the name of the newly configured read/write optical drive using the location code that matches the location of the drive being added    

44. Define commands and process in AIX?

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A command is a request to perform an operation or run a program. A process is a program or command that is actually running on the computer.We use commands to tell the operating system what task you want it to perform. When commands are entered, they are deciphered by a command interpreter (also known as a shell), and that task is processed.

The operating system can run many different processes at the same time. The operating system allows you to manipulate the input and output (I/O) of data to and from your system by using specific I/O commands and symbols. You can control input by specifying the location from which to gather data. For example, you can specify to read input entered on the keyboard (standard input) or to read input from a file. You can control output by specifying where to display or store data. For example, you can specify to write output data to the screen (standard output) or to write it to a file.

Commands : Some commands can be entered simply by typing one word. It is also possible to combine commands so that the output from one command becomes the input for another command.

Processes : A program or command that is actually running on the computer is referred to as a process

45. What is the server message block file system(SMBFS) in AIX?

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Server Message Block File system (SMBFS) allows access to shares on SMB servers as local file systems on AIX. In this file system, the user can create, delete, read, write, and modify the access times of files and directories. The owner or access mode of files and directories cannot be changed.

46. What is a logical partition?

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A logical partition (LPAR) is the division of a computer’s processors, memory, and hardware resources into multiple environments so that each environment can be operated independently with its own operating system and applications

47. Explain network file systems?

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The Network File System (NFS) is a distributed file system that allows users to access files and directories of remote servers as if they were local. Suppose, Server A, that makes its file systems, directories, and other resources available for remote access. Client’s computers, or their processes, that use a server’s resources. Export the act of making file systems available to remote clients. Mount the act of a client accessing the file systems that a server exports.

 48. What is network information service?

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NIS was developed to simplify the task of administering a number of machines over a network. In particular was the requirement to maintain copies of common files (e.g. password, group and host) across different systems.

49. What is a hardware management console?

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The HMC is a server or stand alone machine that provides a graphical user interface tool to manage several Power Systems. The HMC managed system through hypervisor and operating system. From version 7 it is truly web based and you can configure, install and manage, partitioned, virtualization most of your Power5 and 6 boxes via HMC. There are many tasks you can do with HMC, such as,

• Powering off and on of the partition
• Configure and activate resources to the system
• Creates and stores LPAR profiles and allocated resources to them.
• HMC does the dynamic memory reconfiguration of the partition.
• Setup VIO server and VIO client thru HMC and do micro-partition, create storage
• pool and processor pool with it
• Provide virtual console to the partition

Most of the time we installed dual HMC for redundancy and to make sure to achieve more uptime in a wide system.  

50. Why do I need a hardware management console, anyway?

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You need a HMC if you plan to:

• Configure and manage logical partitions and partition profiles (selected models can configure LINUX partitions without a HMC).
• Perform DLPAR (dynamic LPAR) functions.
• Activate and manage Capacity on Demand resources.

You can also use the HMC to:

• Perform service functions
• Manage frames (towers), IOPs and IOAs. * Note that you cannot see below the IOA to the device level.
• Manage system profiles (yes, you can have more than one!)
• Power on and power down. The Service Processor is always hot if there is power to the server.
• Activate and manage Virtualization Engine technologies.
• 5250 emulation so you can get a console up on a i5/OS partition or a virtual terminal window for AIX or LINUX.

51. Does HACMP work on different operating systems?

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Yes. HACMP is tightly integrated with the AIX 5L operating system and System p servers allowing for a rich set of features which are not available with any other combination of operating system and hardware. HACMP V5 introduces support for the Linux operating system on POWER servers. HACMP for Linux supports a subset of the features available on AIX 5L, however this multi-platform support provides a common availability infrastructure for your entire enterprise.

52. How will you change LTG size?

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53. How will you find whether a quorum is up or not?

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54. How to copy a LV from one VG to another?

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Check disk size belong to vg , take two same size disk to mirror

Add one more disk of the same size or already have a disk having rootvg.

Now mirror vg with background sync LV. It sync LVs in background with new LVs

Create a boot image

Add a blv

record of newly added disk, first check and then add.

55. How will you unmirror a VG if a PV gets failed?

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First check the blv record using,

Remove the old blv record, using

Now unmirrorvg

56. How will you change a PP size?

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PP size can be changed using a T-factor. If not then add a partition in VG by adding one disk.

T – Factor?

T – factor means that it will change the pp size to increase the efficiency of vg

Cal-if suppose that datavg pp size is 1016 we can take t factor is 16 then it comes to 2048 and pv contains in vg is 2.

57. What is the default PP Size in AIX?

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128MB

58. How will you rename a VG?

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Unmount all filesystems in VG.

59. What is the major number?

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A major number refers to a type of device. A device number is a major number, and a minor number specifies a particular device of that type or sometimes the operation mode of that device type.

 60. What will you do if a disk gets failed?

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diag command

61. How to enable & disable quorum?

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62. What are the types of error?

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1.H/W error

2.S/W error

3.Operator error

4.Unknown error.

63. What are the severity of the error levels severity?

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1.permanent

2.Temporary

3.Informational

4.Unknown.

64. What is the command to see the error log?

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65. What is the command to clear the error log?

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66. What is the command to increase the size of the error log when it is full?

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67. What is the command to start , stop, restart and list a demon?

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68. When does the error demon start in the boot process?

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rc.boot phase 3

69. What Are The Types Of Odm Databases ?

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• Pre-defined database PdDv, PdAt
• Customised database CuDv, CuAt

70. Give the Odm Commands.

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odmcreate: To customize Odm

To remove ODM: odmdrop

odmdelete: To remove object from ODM

• To see info in ODM  odmget
• To change the fields in object class  odmchange
• To add object to ODM odmadd

71. Types Of Installation?

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• New and complete overwrite
• Migration
• Preservation

72. Where Do Log Files Reside?

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AIX logs messages as specified in /etc/syslog.conf file.

73. How To Unlock User Accounts?

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74. How To Lock A User’s Account?

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75. How Do you Take Backup Of File Systems?

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76. How Will you Restore A File From Already Taking Backup Using Backup?

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77. How Will you Append A File To A Previous Archive Take By Tar?

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78. What Command To Take Backup Other Vg’s?

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79. What Command To Restore Backup Of Non – Rootvg?

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80. Explain the login process to the AIX system.

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• AIX is a multi-user system
• When the user login he needs to provide the user name and password for authentication purposes. After the successful login, AIX starts the SHELL program.

81. Explain the SHELL program.

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• As the user login to the AIX server, the AIX starts the SHELL program.
• The SHELL is a command interpreter.
• It takes the inputs from the users and executes it.
• SHELL is not only the command interpreter it also provides great flexibility to the user.
• SHELL not only reads and executes the commands it also reads the files written in the form of programs and executes them, these shell program files are known as SHELL scripts. The extension of SHELL script is .sh.

82. Name the various SHELL types.

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• sh or Bourne Shell
• bash or Bourne Again shell
• csh or C shell
• tcsh or Turbo C shell
• ksh or the Korn shell

83. List the advantages of Bourne Again Shell or bash.

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• Bash is the GNU shell
• Bash is an sh-compatible shell that incorporates useful features from the Korn shell (ksh) and C shell (csh).
• It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard.
• It offers functional improvements over sh for both programming and interactive uses.
• Interactive usage includes command line editing, unlimited size command history, job control, shell functions and aliases, indexed arrays of unlimited size, and integer arithmetic in any base from two to sixty-four. Bash can run most sh scripts without modification.

84. What is an interactive shell?

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An interactive shell generally reads from, and writes to, a user’s terminal: input and output are connected to a terminal. Bash interactive behavior is started when the bash command is called upon without non-option arguments, except when the option is a string to read from or when the shell is invoked to read from standard input, which allows for positional parameters to be set.

85. Explain the AIX file system.

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• The top level directory is called the root (/) directory that has many subdirectories.
• The file tree is mounted during the system startup.

86. Write the logging in and Out commands in AIX.

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To login in:

To log out:

• If the user ID requires a password, the system will prompt for the password in a similar manner. While the user is typing a password, it does not appear on the screen.
• To terminate the session the user may either enter the exit or logout command, or press the key combination (holding down the Ctrl key while pressing the d key.) logout only works if you are in your login shell.       

87. Write the password change command.

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The passwd command is used to change the user password. The system will start the passwd process which will prompt the user for their old password first. To prevent users being locked out of the system the new password is entered twice. 

88. Which file does that error daemon stay in?

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/usr/lib/errdemon

89. What are the Two states of device availability and explain them?

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Available state and defined state. When a device is in a defined state it means it cannot be used. Not in a ready state. Run cfgmgr try to make it available in the system that device. Available state means that device is ready to use

It displays which disks are available

90. How will you check whether a device is installed or not?

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91. How to change a 64 bit kernel to 32 bit kernel?

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• -Modify the /usr/lib/boot/unix directory and the /unix directory to be   a symbolic link to the binary for the desired kernel.
• -Run the bosboot command to write a new system boot image.
• -Reboot the system.

The path name of the 64-bit kernel is /usr/lib/boot/unix_64, and the

path name of the multiprocessor versions of the 32-bit kernel is

92. How to change a 32 bit kernel to 64 bit kernel?

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To truly change the kernel to 64-bit from 32-bit, the system must be at the AIX® 5.1 or AIX 5.2levels.

It shows a kernel is either 32-bit or 64-bit.

To truly change the kernel to 64-bit from 32-bit, the system must be at the AIX® 5.1 or AIX 5.2levels.

It shows a kernel is either 32-bit or 64-bit.

To change to a 64-bit kernel, enter the following commands:

93. What is VGSA?

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VGSA: Volume Group Status Area contains the information about physical partitions from all physical volumes of the same volume group. It contains the status of VG

94. How to find a system dump?

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95. Where the file does the paging space stay?

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96. How will I check whether a fix is installed or not?

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97. How will you reject a committed fileset?

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98. How will you check whether the service pack is installed or not?

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99. What is the latest OS level?

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100. How will you check whether software is installed or not?

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