Article

jun_sup2001.tar

Questions and Answers

Jim McKinstry and Amy Rich

Q I have an AIX machine where /var keeps filling up, and I need to make it bigger. How do I increase the size of my /var filesystem, and where does the space come from?

A The space comes from the free physical partitions in the volume group in which your partition (the one you want to increase) resides. A volume group consists of physical volumes that are made up of physical partitions. The logical volumes (e.g., /var, /usr, /) then consist of the physical partitions. Your /var logical volume is probably in rootvg, so you can do an:

lsvg -p rootvg

to see the physical volumes in the volume group rootvg. If you have the free physical partitions in rootvg, you can do the following to increase /var to be 100 Mb by doing the following:

chfs -a size='102400' /var

For more information on the Logical Volume Manager, you may want to take a look at IBM's Redbooks (search for LVM):

http://www.redbooks.ibm.com/pubs/html/redbooks/

Q I've heard of some people creating ramdisks under AIX, but I can't find out how from the documentation.

A Ramdisks are a new feature in 4.3.3, and are still unsupported. Prior to that, the best you could hope for was to modify the RAM disk buffer. As of 4.3.3, you can create a ramdisk by doing the following:

mkramdisk <size>
/dev/rramdiskxx
mkfs -V jfs /dev/ramdiskxx
mount -V jfs -o nointegrity /dev/ramdiskxx /your_mount_point

Q Where can I pick up precompiled freeware packages for AIX 4.3?

A IBM has a number of GNU tools precompiled at the following site:

http://www.ibm.com/servers/aix/products/aixos/linux/

There's also another site that carries more packages than just GNU, and the packages are in SMIT-installable format:

http://www-frec.bull.com/linux/index.htm

Q I want to upgrade my AIX machines, but it doesn't boot off the CD-ROM when one is in the drive. How do I make it see the CD-ROM?

A This depends on the model of machine you have. If you have an older machine and there's a key, turn the key to service mode and reboot. If you don't have a key, you can press the "5" key when the machine gets to checking the speaker (it should say "speaker") during the boot process. You can also just change the boot list by doing the following (assuming that your normal boot list is just hdisk0 and your CD is in cd0):

bootlist -m normal cd0 hdisk0

Q How do I create a custom-bootable CD to install new AIX 4.3.3 machines?

A You can use the mkcd command to make a backup image of a system that's installed to your specifications. Using mkcd, you can create three types of CDs: personal system backup, "generic", and non-bootable volume group backup. If you select generic, you can then boot and install any RS/6000 platform (rspc, rs6k, or chrp). This backup requires all the necessary device support, including the MP kernel, to create the boot images for all three platforms. This type of backup also requires a user-supplied and previously created mksysb image. Extra software is needed to create the Rock Ridge format CDs. Take a look in /usr/sbin/mkrr_fs and /usr/sbin/burn_cd for the programs that create the filesystem and write it out to the CD. Also look in /usr/samples/oem_cdwriters for some different vendor-specific sample shell scripts. The mkcd man page includes more information and explains what each flag does.

Q We have an 43P running AIX 4.3 and I am trying to change the network interface from a static IP to using DHCP, but things don't seem to be working correctly. I use smitty and get to the part about the network, and I delete the old IP information. When I exit and go back into smitty, though, they're still there! How do I make my machine a DHCP client?

A We'll say that you're using the ent0 Ethernet interface. Do the following to shut down the interface and remove it:

ifconfig en0 down
ifconfig en0 detach
rmdev -dl en0

Because you've been trying to change things already, you may have already enabled DHCP service, so shut that down:

stopsrc -s dhcpsd

Now use smitty to go create the interface again:

smitty mkinet

Choose "Add a Standard Ethernet Network Interface". It should show that en0 is available. Exit out and run:

smitty mktcpip

filling in all of the required fields. To actually configure the interface to use DHCP, run:

smitty tcpip

and choose "Use DHCP for TCPIP Configuration & Startup". After you press enter, it should create an empty en0 interface using cfgmgr. After it finishes, exit out of smitty again, and you can check to see that the device was created by doing:

lsdev -C|grep en0

Q Where can I get the AIX program Sysback, used to create emergency recovery tapes?

A Sysback (actually called AIX Sysback Backup & Recovery/6000) does not come with AIX. It's a separate product offered from IBM. You can get it by contacting your IBM account representative or reseller, calling 1-800-IBM-4-YOU, or by going to:

http://www.ibm.com/

and clicking on "ShopIBM". There's also a third-party piece of software called Storix Backup Administrator:

http://www.storix.net/

that provides a better interface and more functionality.

Q I'm running AIX 4.3.2 and can't seem to read any man pages with the man command (and catman doesn't work, either). What am I doing wrong?

A The man pages are not installed by default. Most likely you don't have them on your system. Check by doing the following:

lslpp -l | grep bos.html

If you don't see the below sets, you need to install them. You'll need to put in the "Base Documentation" CD-ROM and install the following sets:

bos.html.en_US.cmds.cmds1
bos.html.en_US.cmds.cmds2
bos.html.en_US.cmds.cmds3
bos.html.en_US.cmds.cmds4
bos.html.en_US.cmds.cmds5
bos.html.en_US.cmds.cmds6

Q I'm running AIX 4.3, and I want to reclaim some space from my paging volume (hd6). How would I go about reducing the size of the swap partition when it's always in use by the system?

A IBM has a technote that describes how to do this by creating a new, smaller temporary paging space (assuming you have some free PPs), and then disabling the old one. They highly suggest that you then remake the default paging space on hd6 because some scripts are hardcoded to use it.

http://techsupport.services.ibm.com/cgi-bin/support/
   rs6000.support/techbrowse/
   tbgaus?gaus_mode=9&documents=090605221014598&database=aix

Q How do I turn on large file support on the fly with AIX? What's the maximum file size I can have?

A AIX does not allow turning on large file support on the fly. Large file support is an option that's determined at filesystem creation time. Journaled filesystems on AIX 3.2.5 and preceding versions are limited to 2 GB per filesystem (no large file support). With AIX 4.1, IBM allows filesystems up to 2 GB, and AIX 4.2 and above allows 64 GB files.

Q We're about to upgrade to AIX 4.3.3, but it appears that IBM ships with an ancient version of Sendmail (8.9.3). It claims to have bug fixes and anti-spam features, but it doesn't ship the anti-spam stuff in the configuration file by default. How do I get the anti-spam stuff in my sendmail.cf?

A Your best answer is probably to scrap the installed Sendmail stuff and install the latest Sendmail software from:

http://www.sendmail.org/

You'll need m4, either the GNU version or from the fileset bos.adt.base. If you want to actually stick with what IBM ships you, then you'll want the Sendmail macros from bos.net.tcp.adt and the m4 binary mentioned above. The configuration macros are stored in /usr/samples/tcpip/sendmail, along with READMEs that contain information about generating your own customized sendmail.cf. Be sure to look at /usr/samples/tcpip/sendmail/cf/aix433.mc and /usr/samples/tcpip/sendmail/ostype/aix433.m4. You'll also want to look at the Sendmail 8.9 anti-relaying page:

http://www.sendmail.org/tips/relaying.html

and the Sendmail 8.8 anti-spam page:

http://www.sendmail.org/antispam.html

Q What's the difference between interfaces en0 and et0 under AIX? Should I have both of them?

A En0 and et0 refer to different kinds of framing for the ent0 device. The commonly used frame for TCP/IP is DIX, corresponding to the en0 interface. The et0 interface uses IEEE 802.3 framing. While both framing types can coexist on the wire, the majority of applications these days are TCP/IP, and there's no reason to configure 802.3 for TCP/IP unless you know you have a need for it.

Jim McKinstry is a Senior Sales Engineer for MTI Technology Corporation (www.mti.com). MTI is a leading international provider of data storage management products and services. He can be reached at: jrmckins@yahoo.com.

Amy Rich, president of the Boston-based Oceanwave Consulting, Inc. (http://www.oceanwave.com), has been a UNIX systems administrator for more than five years. She received a BSCS at Worcester Polytechnic Institute, and can be reached at: arr@oceanwave.com.