AIX tips

AIX - Tips n Tricks - Part I

1. To confirm which network adapter is plugged into the switch in IBM AIX

Try this next time to confirm what adapter is actually plugged in to a switch:

This will not only tell you where you have a connection but it will also tell you what speed the port on the switch is.

# netstat -v grep -E "ETHERMedia"
ETHERNET STATISTICS (ent0) :
Media Speed Selected: 100 Mbps Full Duplex
Media Speed Running: 100 Mbps Full Duplex
ETHERNET STATISTICS (ent1) :
Media Speed Selected: 1000 Mbps Full Duplex
Media Speed Running: 1000 Mbps Full Duplex

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2. How to determine if IBM AIX 64 bit kernel (sotware) is installed on your IBM AIX server?

# lslpp -l bos.64bit
bos.64bit 4.3.3.76 COMMITTED Base Operating System 64 bit

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3. How you create a snapshot of your IBM AIX server to send to IBM for tech support ?

This is requried whenver you face issues with your server and you seek help from IBM to sort out the issue.

# snap -gc

This will create a file called snap.pax.Z in the directory /tmp/ibmsupt. Send this file to IBM so that they will get full configuration of your server.

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4. How to enable entended history in AIX 5.3 ?

In AIX 5.3, you have the capability to have a time stamped history. To enable it, just set the following variable:
EXTENDED_HISTORY=ON

Example:
export EXTENDED_HISTORY=ON

If required add this line to your .profile.

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5. How to find the microcode level of tape drives ?

To find microcode level (firmware) of tape drives in IBM AIX:
# tapeutil -f /dev/rmt1 vpd

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6. pgrep and pkill - how to terminate processes ?

You can use the pgrep and pkill commands to identify and stop command processes that you no longer want to run. These commands are useful when you mistakenly start a process that takes a long time to run.

To terminate a process:
a. pgrep - to find out the PID(s) for the process(es)
b. pkill - followed by the PID(s)

The following example illustrates how to find all the processes with a specific name (xterm) and terminate the xterm process that was started last.
# pgrep xterm 17818 17828 17758 18210
# pkill -n 18210

Note: If you need to forcibly terminate a process, use the -9 option to the pkill command.

For Example
# kill -9 -n xterm

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7. How to modify Asynchronous I/O variables in AIX ?

To modify the minservers asynchronous I/O variable (MINIMUM number of servers) in IBM AIX:
# chdev -l aio0 -a minservers='1'

To modify the maxservers asynchronous I/O variable (MAXIMUM number of servers per cpu) in IBM AIX 5L:
# chdev -l aio0 -a maxservers='10'

To modify the maxservers asynchronous I/O variable (MAXIMUM number of servers) in IBM AIX v4.3:
# chdev -l aio0 -a maxservers='80'

To modify the requests asynchronous I/O variable (Maximum number of REQUESTS) in IBM AIX:
# chdev -l aio0 -a requests='4096'

Notes:
1) Valeus will only take effect after a reboot
2) You may use multiple -a options on the same command line3)

The maxservers variable is PER CPU for AIX 5L and TOTAL for AIX v4.3

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8. How to display microcode and firmware levels of the system and adapters in IBM AIX ?

To displays microcode level information for all supported devices in IBM AIX :

# lsmcode -A
sys0!system:SF240_284 (t) SF240_261 (p) SF240_284 (t)
ent0!14108902.DV0210
ent1!14108902.DV0210
ent2!14108902.DV0210
ent3!14108902.DV0210
sisscsia0!44415254.05080064
sisscsia1!44415255.050A0064
hdisk0!ST37320.4A553042.43373038
hdisk1!ST37320.4A553042.43373038

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9. How to determine if simultaneous multi-threading (SMT) is enabled in AIX ?

Your system is capable of SMT if it's a POWER5-based system running AIX 5L Version 5.3.To determine if it is enabled:# smtctl

To enable SMT: # smtctl -m on [ -w boot now]
To disable SMT: # smtctl -m off [ -w boot now]

Note: If neither the -w boot or the -w now options are specified, then the mode change is made immediately. It persists across subsequent reboots if you run the bosboot command before the next system reboot.

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10. How to find top users of memory space in IBM AIX ?

To list the top ten users of paging space in IBM AIX:
# svmon -Pgt 10

To list the top ten users of realmem in IBM AIX:
# svmon -Put 10

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11. How to list the filesystems in a volume group in IBM AIX ?

# lsvgfs volume_group

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12. How to query the volume group descriptor area on a drive in IBM AIX ?

To query the volume group descriptor area on the drive, so you can find out if there's a VG on the disk, even if there isn't anything imported on the drive in IBM AIX:

# lqueryvg -Atp hdisk#

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13. How to set IBM AIX for full core dumps and files to unlimited

To set IBM AIX for full core dumps to unlimited:
# ulimit -c unlimited

To set IBM AIX for files to unlimited:
# ulimit -f unlimited

To view your ulimit settings:
# ulimit –a

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14. How to determine what the speed and duplex is of an interface in AIX ?

# entstat -d en0 grep "Media Speed"

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15. How to find the highest technology level and service pack installed in IBM AIX ?

Starting in 2006, in IBM AIX, a Maintenance Level will be referred to as a Technology Level and will only be released twice per year.

The Service Pack concept will allow service-only updates (as known as PTF’s) that are released between Technology Levels to be grouped together for easier identification.
Sample output for a V5.3 system, with Technology Level 4, and Service Pack 2 installed would be:

# oslevel –s

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16. How to find number of active processors in IBM AIX ?

To find the number of active processors in IBM AIX:
# bindprocessor -q
The available processors are: 0 1 2

To find the number of processors installed (but not necessarily available):

# lscfg -v grep proc
proc0 00-00 Processor
proc2 00-02 Processor
proc4 00-04 Processor

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17. How to read the contents of /etc/security/failedlogin in IBM AIX ?
# who /etc/security/failedlogin# /usr/sbin/acct/fwtmp < /etc/security/failedlogin ---------------------------------------------------------------------------------------------------------------- 18. How to reserve or lock a terminal under AIX 5L ? This command will lock your terminal and reserve it for later use in AIX 5L # lock # lock -30 (lock for 30 minutes) Note: default lock time is 15 mintes lock will ask you for a password twice then lock the terminal. you can unlock it by entering the password a third time. ---------------------------------------------------------------------------------------------------------------- 19. How to stop IBM AIX from forcing a user to change their password at first login ? # pwdadm -c username ---------------------------------------------------------------------------------------------------------------- 20. Redhat Package Manager for IBM AIX and Linux To query all packages installed: # rpm -q –a To list file in a specific package: # rpm -q -l package.rpm To install a RPM package: # rpm -i package.rpm To delete (erase) a RPM package: # rpm -e package.rpm To query for RPM package owning file: # rpm -q -f /path/to/file To upgrade a RPM package # rpm -U package.rpm ---------------------------------------------------------------------------------------------------------------- 21. How to capture TCPIP packet information in IBM AIX ? Here is a command to capture TCP/IP packet information between your server and another in IBM AIX: Become root user, Find a temporary directory to capture the data (/tmp in this example) Run the iptrace command: # iptrace -a -d host_destination -b /tmp/ip.out iptrace will run in the background and results will be in /tmp/ip.out To see the results of the trace: # ipreport /tmp/ip.out more Don't foregt to kill iptrace when you're done: # ps -ef grep iptrace grep -v grep awk '{system("kill " $2)}' Some other cool options of iptrace: -d : specify destination IP address -s : specify origin IP address -b : show 2-way traffic (as in "-s xxx -b" or "-d xxx -b") -a : no ARP requests (less pollution in the trace) To see all packets going in and out of server, unixserv, without ARP requests: # iptrace -a -d unixserv -b /tmp/ip.out iptrace and ipreport are in IBM AIX LPP "bos.net.tcp.server" ---------------------------------------------------------------------------------------------------------------- 22. How to check if a system dump completed successfully on IBM AIX ? To verify if a system dump completed successfully on an IBM AIX server: # sysdumpdev –L 0453-039 Device name: /dev/hd6 Major device number: 10 Minor device number: 1 Size: 124371456 bytes Date/Time: Sun Sep 15 12:19:02 EDT 2002 Dump status: 0 ( 0 = Ok) dump completed successfully 0481-195 Failed to copy the dump from /dev/hd6 to /var/adm/ras ---------------------------------------------------------------------------------------------------------------- 23. How to check two file systems simultaneously on different drives in IBM AIX ? To check two file systems simultaneously on different drives in IBM AIX.The dfsck command permits you to interact with two fsck commands at once. To aid in this, the dfsck command displays the file system name with each message. When responding to a question from the dfsck command, prefix your response with a 1 or a 2 to indicate whether the answer refers to the first or second file system group. # dfsck [ FlagList1 ] FileSystem1 [ FlagList2 ] FileSystem2 Example to check two filesystems: # dfsck -p /dev/hd1 - -p /dev/hd7 Note: you can also specify the file system names found in the /etc/filesystems. Attention: Do not use the dfsck command to check the root file system. ---------------------------------------------------------------------------------------------------------------- 24. How to make a disk flash in IBM AIX ? For disk replacement, it is often useful to make the disk flash so that you know which disk to replace in IBM AIX: # diag to continue Select "Task Selection (Diagnostics, Advanced Diagnostics, Service Aids, etc.)" Select "Hot Plug Task"Select "SCSI and SCSI RAID Hot Plug Manager" Select "Identify a Device Attached to a SCSI Hot Swap Enclosure Device" Select the slot you wish the disk to flash Replace the appropriate disk by checking which disk is flashing ---------------------------------------------------------------------------------------------------------------- 25. How to determine which application created the OS core file in AIX ? # /usr/sbin/lquerypv -h /path/to/core 6b0 64 The output of this command is neat, clean and easy to read. Here is an example: # lquerypv -h core 6b0 64 000006B0 7FFFFFFF FFFFFFFF 7FFFFFFF FFFFFFFF ................ 000006C0 00000000 000007D0 7FFFFFFF FFFFFFFF ................ 000006D0 00120000 1312C9C0 00000000 00000017 ................ 000006E0 6E657473 63617065 5F616978 34000000 netscape_aix4... 000006F0 00000000 00000000 00000000 00000000 ................ 00000700 00000000 00000000 00000000 00000ADB ................ 00000710 00000000 000008BF 00000000 00000A1E ................ The executable is located between the pipes on the right hand side of the output. In this case, the core was generated by Netscape. ---------------------------------------------------------------------------------------------------------------- 26. How to find the system id number of an IBM AIX server ? # lsattr -El sys0 -a systemid # uname -u # lscfg -vpgrep -p "System VPD:" grep -i Serial Note: commands may not work on all IBM models ---------------------------------------------------------------------------------------------------------------- 27. Tips on Memory Tuning : Do not use the command vmtune in AIX 5L. From AIX 5L. vmo and ioo commands are introduced to tune memory and I/O. Here is how we set various memory options now: # vmo -p -o maxfree=128 # vmo -p -o minperm%=5 # vmo -p -o maxclient%=10 # vmo -p -o maxperm%=10 # vmo -p -o maxfree=632 # vmo -p -o minfree=600 # ioo -p -o maxpgahead=32 To see the results of the changes: # vmo –L # ioo –L If you have a problem with slow telnet sessions: # chdev -l sys0 -a maxpout='33' -a minpout='24' To set AIO (asynchronous IO) options use smitty ---------------------------------------------------------------------------------------------------------------- 28. If you reinstall an IBM AIX server and the mksysb used was for a server on another vlan, you can end up with 2 default routes. Lets see how to solve this issue In order to see the default routes stored in the ODM: # lsattr -El inet0 grep Route route net,-hopcount,0,,0,172.26.247.92 Route True route net,-hopcount,0,,0,172.26.14.1 Route True To see the default routes you have in your routing table: # netstat -rn grep default default 172.26.14.1 UGc 0 0 en0 - - =>
default 172.26.247.92 UGc 0 0 en0 - -

To remove one of the default routes, use smitty and not a the route command otherwise you will end up with 2 default routes after a reboot.

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29. EFix - How to manage ?

To list efix :
# emgr –l

To install an efix package:
# emgr -e efixPackage

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30. Kernel Processes in AIX: An Overview

# ps -kl
# pstat -a (as root)

There are several kprocs, and they do a number of things. Often they have fixed priority and will run ahead of any user processes.

A couple are:
Kproc Kernel (wait) wait process
Kproc Kernel (lrud) Least Recently Used Daemon (mem mgmt)
Kproc Kernal (swapper) Memory/Process swapping ?
Kproc Kernel (kbiod) Kernel Block I/O daemon (disk I/O)?
kproc Kernel ( gil) 1032 Networking off-level stuff
Kproc Kernel (netm) Network memory allocator
Kproc Kernel (aump) Automounter

A kproc is a kernel process, started by the kernel on behalf of either another kernel process, or as a result of an application initiating a system call or call to a kernel service.
Wait - You will find that the "wait" kproc will have accumulated a lot of cpu time. This just means your system is idle a lot. When nothing else needs to run, the wait kproc is charged the time slice

GIL - "Global ISR List"
ISR->Interrupt Service Routines - multithreaded kproc runs at fixed pri of 37 Used to process various timers (tcp, streams, ....) and also used to pass packets from demux layer to IP layer for non-CDLI drivers.

ps -lk
The processes with nice value of -- are running with fixed priorities. Their nice values can not be changed. On my system that would processes such as swapper (pid=0, pri=16) and the wait kproc (pid=514, pri=127).

This will list out all the kprocs. Now do a pstat -a to find what they really are?
This will show you the real name of the kproc.

Aump kernel thread is left over after you stop the automounter daemon.
Yes. It goes away after reboot. However, there is an APAR for it: IY33240

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31. How to manage network tuning parameters in AIX ?

The no command is used to configure network tuning parameters in IBM AIX. The no command sets or displays current or next boot values for network tuning parameters. This command can also make permanent changes or defer changes until the next reboot.

Syntax:
no [ -p -r ] { -o Tunable[=NewValue] }
no [ -p -r ] {-d Tunable }
no [ -p -r ] { -D }
no [ -p -r ] -a
no -h [ Tunable ]
no -L [ Tunable ]
no -x [ Tunable ]

where:
-a : displays current, reboot or permanent value for all tunable parameters
-d : resets Tunable its to default value
-D : resets all tunables to their default value
-h : displays help about Tunable parameter
-L : lists the characteristics of one or all Tunables
-o : displays the value or sets the Tunable to NewValue
-p : makes changes apply to both current and reboot values (I heard this option in many interviews)
-r : makes changes apply to reboot values (I heard this option in many interviews)
-x : lists characteristics of one or all tunables using spreadhset format

Example to set the value of tunable tcp_sendspace to 65536 permanently:
# no -p -o tcp_sendspace=65536

Example to set the value of tunable sb_max to 2097152 at next reboot:
# no -r -o sb_max=2097152

Example to display all values of tunables:
# no -a

Example to display all values of tunables at next reboot:
# no -r -a

Example to set the value of tunable tcp_sendspace to 65536:
# no -o tcp_sendspace=65536

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32. How to verify your ntp setup is working properly ?

# ntpq -c peersremote refid st t when poll reach delay offset disp =========================================================================
*time.domain.co doghaus.cns.uto 3 u 12 64 177 1.46 -2.515 145.19

If you have a star (*) in the first column of the name of the time server, your time is being synchronised properly.

The third column, st, is the stratum. The lower the number, the closer you are to the time source.

Stratum 16 means you are not synchronised.

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33. How to syncronise your server time to a time server ?

If you don't want to run NTP (network time protocol), you can update your system time with the command:

# ntpdate timeserver.domain.com

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34.How to list open files ?

To list all open files:
# lsof

To list all open files on a device:
# lsof /dev/hd4

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35. How to find the world-wide name (WWN) or network address of a fibre-channel (FC) card in IBM AIX ?

First find the name of your fibre-channel cards:
# lsdev -vp grep fcs

Then get the WWN (for fcs0 in this example):
# lscfg -vp -l fcs0 grep "Network Address"

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36. How to change a server hostname with the uname command in IBM AIX ?

To display the current hostname
# uname -n
localhost

To change the hostname
# uname -S newhostname

Again display the hostname
# uname -n
newhostname

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37. How can you find out when a system was installed?
Enter the following command:
lslpp -h bos.rte
The output of this command will show the history of when the operating system was installed. Read the entry for the AIX level (ie, 4.3.3.0).

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38. How to make sure all of the user definitions are correct in the user database

#usrck -n ALL

Do the same for the groups:
#grpck -n ALL

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39. Reduce the Size of a File System in Your Root Volume Group ?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_baseadmn_rootvg_reduce.htm#baseadmn_rootvg_reduce
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40.How to reset an Unknown Root Password ?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_baseadmn_recoverrootpswd.htm#baseadmn_recoverrootpswd
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41. How to configure Domain Name Servers ?http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_commadmn_dns.htm#commadmn_dns

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42. How to re-create corrupted boot image ?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_baseadmn_bad_boot_img.htm#baseadmn_bad_boot_img
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43. How to configure NIM master server using EZNIM ?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_insgdrf_configure_eznim.htm#insgdrf_configure_eznim
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44. How do I use network (For normal users)

http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto_user/Use_Network_U.htm#category_use_network

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45. How do I view system and environment information?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto_user/AccessSys_Envir_U.htm#category_accesssys_envir
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46. How do I use shell scripts ?http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto_user/Use_Shells_U.htm#category_use_shells
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47. How do I redirect standard input, output, and error?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto_user/RedirStand_IO_Error_U.htm#category_redirstand_io_error
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48. How do I make my system more secure?
http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto_user/Security_U.htm#category_security


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49. How to configure network adapters for Redundancy ?
http://users.ca.astound.net/~baspence/AIXtip/etherchannel.htm
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50. Useful link about AIX Error Log codes, LED codes, 7-Digit Error codes.http://rainsux.dyndns.org/AIX5L-Messages-Codes.html

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51. How to disable remote root login ?

When multiple users have root access to a system, a common security question is who logged in as root? One alternative is to disable remote logins for the root id (chuser -rlogin=false root). This forces users to first login in with their regular user id, then "su -" to root. All "su" activity is captured in /var/adm/sulog, thus answering the question of "who logged in as root."
Comment: In general it is a good practice to disable root remote access as it provides two layers of password protection.

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52. Replacing a disk drive in AIX.

http://users.ca.astound.net/~baspence/AIXtip/download/failed_disk.pdf

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53. How to enabling Non-root Users to Administer Passwords ?

The AIX pwdadm command can be used to offload password administration to non-root administrators. The pwdadm command allows the administrator to change anothers password, or force users to change their password at the next login. To enable a non-root administrator to use pwdadm, simply add their ID to the "security" group.
For more information: http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds4/pwdadm.htm

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54. Fun with device locations

Here are a few commands to locate physical devices. These commands are useful in a partitioned environment where locations are virtual.
lsdev -Cc adapter -s pci - list all adapter slots lsdev -p adapter - lists devices owned by an adapter lsdev -Cl adapter -F parent lists the parent adapter for a device (like a disk drive) lsdev -Cl adapter - virtual device location (for LPARs) lscfg -vl adapter - actual device location So, for example, to locate the physical adapter connected to hdisk0:
# Identify the parent adapterlsdev -Cl hdisk0 -F parent
# Locate the parent adapter lscfg -vl parent

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55. How to automate setting passwords ?

The "chpasswd" command is easier to use than "passwd" when setting a list of user passwords. It can be used from the command line or shell script. For example, to change passwords for users listed in a file, type the following
cat mypasswords chpasswd
Where the mypasswords file contains
user1:password1user2:password2......

For more information see the following URL

http://publib16.boulder.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds1/chpasswd.htm

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56. How to list files if 'ls' is missing or corrupt ?
echo *

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57. How to change the timezone and language in /etc/environment ?
chtz (timezone eg GMT0BST)
chlang (language eg En_GB)

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58. Find large files

How do you find really large files in a file system:

find . -size +1024 -xdev -exec ls -l {} \;

The -xdev flag is used to only search within the same file system, instead of traversing the full directory tree. The amount specified (1024) is in blocks of 512 bytes.

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59. Montoring a system without logging in

Let's say you have a helpdesk, where they must be able to run a script under user-id root to check or monitor a system:

First, create a script, you wish your helpdesk to run.

Modify your /etc/inetd.conf file and add:
check stream tcp wait root /usr/local/bin/script.sh
where script.sh is the script you've written.

Modify your /etc/services file and add:
check 4321/tcp

You may change the portnumber to anything you like, as long as it's not in use.

Now, you may run:
telnet [system] 4321
and your script will be magically run and it's output displayed on your screen. If the output of the script isn't displayed on your screen very long, just put a sleep command at the end of your script.
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60. Changing maxuproc requires a reboot?
When you change MAXUPROC (Maximum number of processes allowed per user), the smitty help panel will tell you that changes to this operating system parameter will take effect after the next system reboot.
This is wrong Help information. The change takes effect immediately, if MAXUPROC is increased. If it is decreased, then it will take effect after the next system reboot.
This help panel text from smitty will be changed in AIX 5.3. APAR IY52397.
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61. Defunct processes
Defunct processes are commonly known as "zombies". You can't "kill" a zombie as it is already dead. Zombies are created when a process (typically a child process) terminates either abnormally or normally and it's spawning process (typically a parent process) does not "wait" for it (or has yet to "wait" for it) to return an exit status.
It should be noted that zombies DO NOT consume any system resources (except a process slot in the process table). They are there to stay until the server is rebooted.
Zombies commonly occur on programs that were (incompletely) ported from old BSD systems to modern SysV systems, because the semantics of signals and/or waiting is different between these two OS families.
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62. DLpar with DVD-ROM
Adding a DVD-ROM with DLpar is very easy. Removing however, can be somewhat more difficult, especially when you've run cfgmgr and devices have been configured.
This is how to remove it:
#rmdev -dl cd0
(Remove all cdrom devices found with lsdev -Cc cdrom)
#rmdev -dl ide0
Then remove the devices found with
# lsdev -C grep pci
All PCI devices still in use, can not be removed. The one not in use, is the PCI device where the DVD-ROM drive on was configured. You have to remove it before you can do a DLPAR remove operation on it.
Now do your DLPAR remove operation n HMC
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63. How do you send an attachment via mail from AIX ?
Uuencode is the answer:
uuencode [source-file] [filename].b64 mail -v -s "subject" [email-address]
For example:
# uuencode /etc/motd motd.b64 mail -v -s "Message of the day" email@hostname.comI
use the .b64 extension which gets recognized by Winzip. When you received your email in Outlook, you will have an attachment, which can be opened by Winzip.
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64. FTP umask
A way to change the default 027 umask of ftp is to change the entry in /etc/inetd.conf for ftpd:
ftp stream tcp6 nowait root /usr/sbin/ftpd -l -u 117
This will create files with umask 117 (mode 660).
Using the -l option will make sure the FTP sessions are logged to the syslogd. If you want to see these FTP messages in the syslogd output, then you should add in /etc/syslog.conf:
daemon.info [filename]
AIX - Tips n Tricks - Part II

1. How to configure the system and create a restricted shell user ?
Below example shows how to create a restricted shell user (this user can execute only "ls" and "vi" commands
a) Make a reduced bin directory to contain links to programs for the user or users:
# mkdir /usr/rbin
b) Link the necessary commands and programs in the reduced bin directory.
For example, give access to the ls and vi commands:
# ln -s /usr/bin/ls /usr/rbin/ls
# ln -s /usr/bin/vi /usr/rbin/vi
c) Add Rsh as a valid shell in /etc/security/login.cfg:
# vi /etc/security/login.cfg
d) Add /usr/bin/Rsh to the list of shells in the usw stanza:
usw:
shells = /bin/sh,/bin/bsh,/bin/csh,/bin/ksh,/bin/tsh,/bin/ksh93,/usr/bin/sh,
/usr/bin/bsh,/usr/bin/csh,/usr/bin/ksh,/usr/bin/tsh,/usr/bin/ksh93,/usr/sbin/
uucp/uucico,/usr/sbin/sliplogin,/usr/sbin/snapp,/usr/bin/Rsh
e) Add the restricted shell user:
# mkuser shell="/usr/bin/Rsh" alex
f) Assign an initial password:
# passwd alex
g) Change the ownership of the users profile to root:
# chown root:system /home/alex/.profile
h) Change the permissions of the users profile to 755:
# chmod 755 /home/alex/.profile
i) Edit the users profile setting the PATH and Shell variables:
# vi /home/alex/.profile
Set PATH for the new bin directory and Set SHELL to rksh:
PATH=/usr/rbin; export SHELL=/usr/bin/Rsh
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2. How to change the default welcome (herald) message on the login display ?
Edit the file /etc/security/login.cfg and update the herald parameter ...
default:
herald = "Unauthorized use of this system is prohibited\n\nlogin: "
sak_enable = false
logintimes =
logindisable = 0
logininterval = 0
loginreenable = 0
logindelay = 0
You can also use the below command to change the herald value

# chsec -f /etc/security/login.cfg -a default -herald "Unauthorized use of this system is prohibited.\n\nlogin: "
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3. How to set automatic logoff (only for terminals) ?
Edit the /etc/security/.profile file to include an automatic logoff value for all users, as in the following example:
TMOUT=600 ; TIMEOUT=600 ; export readonly TMOUT TIMEOUT
The number 600, in this example, is in seconds, which is equal to 10 minutes. However, this method only works from the shell.
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4. How to auto forward the mails ?
Create $HOME/.forward file and add adresses or aliases.
When mail is sent to a local user, the sendmail command checks for the $HOME/.forward file.
If the file exists, the message is not sent to the user. The message is sent to the addresses or aliases in the $HOME/.forward file.
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5. How to set(define) and unset a variable in a shell or shell script ?
# x=3 -> Defines a vlue for a variable 'x'
# echo $x -> Displays the vlue of 'x' vairable
3
# unset x -> Unsets the variable
# echo $x -> Again display its value
#
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6. How to send file1 as a message to user alex ?
# mail alex <>
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7. How to display mail queue ?

Note: mailq is the queue where your mails are stored
# mailq (or) sendmail -bp
There is 1 request in the mail queue
---QID---- --Size-- -----Q-Time----- ----------Sender/ Recipient-----------
OAA 19258 * 29 Mon Jun 26 14:57 root
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8. Whats sendmail command?
It receives formatted messages and routes messages to one or more users. IT can deliver messages to users on local/remote machines. It will be started by tcpip sub-system . It uses /etc/mail/sendmail.cf as config file.
Once this daemon started, you can find its process id in
/etc/sendmail.pid.

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9. How to define mail aliases for users?
a) Add the aliases to /etc/aliases.
For Example,
nobody: /dev/null
certify: user02, user5801@server3, root@server4, user5911@se
b) Rebuild the aliases database using
newaliases (or) sendmail -bi
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10. If logging with telnet takes long time (for ex. 2 mins), what might be the issue?
There might be problem with DNS resolution. Check /etc/resolv.conf and check dns connection thru nslookup command.
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11. While attempting to log in, you see the below message. How you solve this issue ?
'All available login sessions are in use.'
Check the number of AIX user license using "lslicense"
If required increase the license using "chlicense" command.
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12. Oracle DBA says that his database is not able to go beyond certain limit. For example, oracle userid is not able to start more than 500 process's. Whats the issue?
This is because of the "maxuproc" value is 500. Check the value using "lsattr -El sys0 -a maxuproc"
If required change the value using
# chdev -l sys0 -a maxuproc=1000
Normally for Oracle Production machines, you have to consult with DBA's while installing the server and set an agreed value.
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13. Errpt is not displaying any reports. Found that /var/adm/ras/ errlog file is there in the location and errdemon is running fine. What might be the issue the issue?
errlog file seems to be corrupted. Delete the file and stop the errdemon (/usr/lib/errstop).
Start the errdaemon (/usr/lib/errdemon). While starting, daemon creates the errlog file automatically.
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14. How to list IDE controllers in your system ?
# lscfg -l ide*
DEVICE LOCATION DESCRIPTION
ide0 01-00-00 ATA/IDE Controller Device
ide1 01-00-01 ATA/IDE Controller Device
The following sample display from the lscfg -l ide command shows
There are 2 IDE I/O controllers configured in the server
Controller ide0 and ide1 are located on the system planar ( Notice 1st and 2nd digits in location code)

The planar indicator is the second digit in the location value with a value of 1.


6th digit indicates the controller number.
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15. After a successful login, the login command displays the message of the day, the date and time of the last successful and unsuccessful login attempts for this user, and the total number of unsuccessful login attempts for this user since the last change of authentication information (usually a password).
How do you suppress these messages?
You can suppress these messages by creating a “.hushlogin” file in your home directory.
For Example,
At the prompt in your home directory, type the following:
# touch .hushlogin
The touch command creates the empty file named .hushlogin if it does not already exist. The next time you log in, all login messages will be suppressed. You can instruct the system to retain only the message of the day, while suppressing other login messages.
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16. Whats the files system read once you login ?
First File : /etc/environment - contains variables specifying the basic environment for all processes.
Second File: /etc/profile - controls system-wide default variables
Third File : $HOME/.profile - lets you customize your individual working environment
Fourth File: $HOME/.env - lets you customize your individual working environment variables.
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17. How to override variables defined in /etc/environment for a particular user?
A fourth file that the operating system uses at login time is the
$HOME/.env file, if your .profile contains the following line:
export ENV=$HOME/.env
The .env file lets you customize your individual working environment variables. The .env file contains the individual user environment variables that override the variables set in the /etc/environment file. You can customize your environment variables as desired by modifying your .env file.
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18. How to change the font in AIX ?
To change the font to an italic, roman, and bold face of the same size, type the following:
# chfont -n /usr/lpp/fonts/It114.snf /usr/lpp/fonts/Bld14.snf /usr/lpp/
> fonts/Rom14.snf
You can also use smitty chfont.
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19. How to run a process in the background ?
For Ex, to run script1.sh in background run
# script1.sh &
But this script process gets killed if you close the terminal
So always practice to run using nohup,
# nohup script1.sh &
Usage of nohup doesn't kill the process if you close the telnet session. Output from the process/script will be stored in a file called nohup.out in the directory from where you started the process.
This will help you in case if you want to start backup using mksysb and close your terminal/ leaving office, you can safely use "nohup command &". Next day morning, you can view the contents of nohup.out to know the status of the backup job.
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20. What is the default priority for a process?
Default priority is 0. Priority numbers is in the range of -20 to 20. Highest number is the lowest priority and lowest number has high priority while using resources.
To set the priority while start a process, use nice command.

If the process is already running, you can use "renice" command to change its priority.
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21. How to stop, resume and to make it foreground process?
To stop(pause) a foreground process, use
Cntrol + Z keys ie., Ctrl+Z.


Note: Ctrl+Z works in the Korn shell (ksh) and C shell (csh), but not in the Bourne shell (bsh).
To restart a stopped process, you must either be the user who started the process or have root user authority.
To restart a stopped process, enter
# kill -19 pid
To run it in foreground, enter
# fg pid

where pid is the process id which can be obtained from the following command
ps -ef | grep precess_name | awk '{print $2}'
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22. How to display a program output as well as copying to a file ?
Normally usage of output redirection suppresses the output on screen.

Ex. ls -l > file1
If we want to redirect the output as well as show the output in screen use the tee command.
Ex: ls -l | tee -a file1
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23..How to capture your terminal screen to a file ?
To capture the screen of a terminal, at the prompt, type the following:
#script
The system displays information similar to the following:
Script command is started. The file is typescript.
Everything displayed on the screen is now copied to the "typescript" file.
To stop the script command, press Ctrl-D or type exit and press Enter.
The system displays information similar to the following:
^D


Script command is complete. The file is typescript.
Use the cat command to display the contents of your file.
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24. What are the supported file systems in AIX ?
a) JFS (or) JFS2 - Disk based file system
b) NFS - Network based File system
c) CDRFS - CDROM based file system
d) UDFS - DVD-ROM based file system
e) RAMFS - RAM based file system used while booting the system
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25. What are the different directory abbreviations?
Abbreviation Meaning
. The current working directory
.. The parent of the current working directory
~ Your home directory
$HOME Your home directory
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26. What are the different directory path names ?
Absolute path name:
Traces the path from the /(root) directory. Absolute path names always
begin with the slash (/) symbol.
Ex. /home/ raja/dir1

Relative path name:
Traces the path from the current directory through its parent or its
subdirectories and files. As user "raja", I can say ./dir1 since I'm already in /home/raja
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27. How to move a directory ?
# mvdir book manual
This moves the book directory under the directory named manual, if the
manual directory exists. Otherwise, the book directory is renamed to manual.
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28. What the RAID groups AIX LVM supports?
RAID-0 - Striping
RAID-1 - Mirroring
RAID-10 (or) RAID 0+1 - Mirroring and striping
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29. How to read and remove mails from my system mailbox?
At your system command line prompt, enter the mail command:
# mail
If there is no mail in your system mailbox, the system responds with a message:

No mail for YourID
If there is mail in your mailbox, the system displays a listing of the messages in your system mailbox:
# mail
Here Type ? for help.

"/usr/mail/lance": 3 messages 3 new
>N 1 karen Tue Apr 27 16:10 12/321 "Dept Meeting"
N 2 lois Tue Apr 27 16:50 10/350 "System News"
N 3 tom Tue Apr 27 17:00 11/356 "Tools Available"
The current message is always prefixed with a greater-than symbol (>).
Each one-line entry displays the following fields:
status - Indicates the class of the message.
number - Identifies the piece of mail to the mail program.
sender - Identifies the address of the person who sent the mail.
date - Specifies the date the message was received.
size - Defines the number of lines and characters contained in the
message (this includes the header).
subject - Identifies the subject of the message, if it has one.
The status can be any of the following:
N - A new message.
P - A message that will be preserved in
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30. After logging as an application user (oradba), when I issued "crontab -l" system throwed the below error
0481-103 Cannot open a file in the /var/spool/cron/crontabs directory.
What is the solution?
Here is the solution
a) Create an empty file /var/spool/cron/crontabs/oradba
b) Change the ownership of the file to root.cron
c) Login as oradba and issue "crontab -l" to verify the cron.
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31. How to identify the program listening in the given port ?
METHOD I: # lsof –P –n –i :505 (for port 505)
METHOD II:
# netstat -Aan|grep 9404
f100060006952b98 tcp 0 0 *.9404 *.* LIST
EN
f100060006a90b98 tcp 0 0 *.19404 *.* LIST
EN
# rmsock f100060006952b98 tcpcb
The socket 0x6952808 is being held by proccess 753870 (java).
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32. How to display non-printable characters in a text file ?
Lets create a file with non-printable characters.
# vi filename.txt
^I^I^I^I$
$
$
$
this is a test$
^I^I^I^I$
~
: set list
Now we will list the file so that non-printable chars are viewed
# cat -vet filename.txt
^I^I^I^I$
$
$
$
this is a test$
^I^I^I^I$
# od -c filename.txt
0000000 \t \t \t \t \n \n \n \n t h i s i s
0000020 a t e s t \n \t \t \t \t \n
0000034
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33. How to display specific lines in a text files ?
For illustration purposes, I'm using the cat -n filename to show the line numbers in this script.
# cat -n filename
...
8 for i in $*
9
10 do
11
12 typeset -i16 hex
13 hex=$i
14 print $i equals $hex in hexadecimal
15
16 typeset -i8 oct
17 oct=$i
18 print $i equals $oct in octal
19
20 typeset -i2 bin
21 bin=$i
22 print $i equals $bin in binary
23
24 print
25 done
...
Prints out the for loop without displaying the line numbers
# sed -n 8,25p filename | tee for_loop
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34. How to recover the root password in AIX ?
If you forgotten the root password, we can easily recover it but the system requires 2 recycles.
Here is the way I follow
Password recovery is one of the simplest troubleshooting procedure in
AIX. Once you boot from CD, you see a menu with 3 menu items.
In that select the 3rd item
ie., "Start Maintenance Mode for System Recovery" à


"Access a Root Volume Group" ->
"Access this volume group and start a shell".
This will open a shell prompt. The just use "passwd" command for
setting a new password for root.
Thats it. root password has been changed.
Now you can reboot the machine from rootvg hard disk (normally it should be hdisk0)
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34. How to find out the (real) memory usage ?
# svmon -G
size inuse free pin virtual
memory 2097152 2097026 126 195637 1237158
pg space 524288 61023
work pers clnt lpage
pin 195404 233 0 0
in use 1189840 906786 400 0
The size and inuse columns of the memory and pgspace output represent real memory and paging space usage respectively.
The size is measured as the number of 4K pages.
Here in this case used memory is
= ((2097026 x 4)/1024)/1024 GB of used memory
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35. Here are some of the errors you get when paging space is low.
INIT: Paging space is low!
ksh: cannot fork no swap space
Not enough memory
Fork function failed
fork () system call failed
Unable to fork, too many processes
Fork failure - not enough memory available
Fork function not allowed. Not enough memory available.
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36. How is the default paging space size determined ?
It follows the following standard
Set paging space to 2 times the amount of RAM
Paging space can use no more than 20% of total disk space in the root volume Group
Paging space can be no larger than 2 GB