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):
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:
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:
There's also another site that carries more packages than just
GNU, and the packages are in SMIT-installable format:
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
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:
Choose "Add a Standard Ethernet Network Interface". It should
show that en0 is available. Exit out and run:
filling in all of the required fields. To actually configure the interface
to use DHCP, run:
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:
and clicking on "ShopIBM". There's also a third-party
piece of software called Storix Backup Administrator:
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:
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.
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
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:
and the Sendmail 8.8 anti-spam page:
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: firstname.lastname@example.org.
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: email@example.com.