• Insert the product media for the same version and level as the current installation into the appropriate drive.
• Power on the server.
• Boot the server into SMS mode and Choose Start Maintenance Mode for System Recovery.
• Select Access a Root Volume Group. A message displays explaining that you will not be able to return to the Installation menus without rebooting if you change the root volume group at this point.
• Type the number of the appropriate volume group from the list.
• Select Access this Volume Group and start a shell.
• At the prompt, type the passwd command to reset the root password.
• To write everything from the buffer to the hard disk and reboot the system, type the following:

  # sync;sync;sync;reboot

Here's a simple command to convert a hexadecimal number to decimal. For example if you wish to convert hexadecimal "FF" to decimal:

# echo "ibase=16; FF" | bc
255

On occasion I have the need to establish trust relationships between Unix boxes so that I can script file transfers. In short, here's how you leverage SSH to do that. Using the example of trying to connect from server "a" to get a file on "b" follow this example:

• Connect to "a".
• Type: ssh-keygen -t rsa
• The default directory for keyfiles will be ~/.ssh/ (if you do not want to be prompted, leave passphrase blank).
• Copy the contents of .ssh/id_rsa.pub (there should only be one line).
• Place this line on "b", in ~/.ssh/authorized_keys.

When you have a lot of Putty screens, or if you frequently login to a host through a jump server, it's very easy to set the title of the Putty window, for exmaple to the hostname of the server you're currently logged into. This way, you'll easily recognize each telnet screen, and avoid entering -possibly destructive- commands in the wrong window:

echo "\033]0;`hostname`\007"

HACMP is capable of using an alternative MAC address in combination with its service address. So, how do you set this MAC address without HACMP, just using the command line? (Could come in handy, in case you wish to configure the service address on a system, without having to start HACMP).

# ifconfig enX down
# ifconfig enX detach
# chdev -l entX -a use_alt_addr=yes
# chdev -l entX -a alt_addr=0x00xxxxxxxxxx
# ifconfig enX xxx.xxx.xxx.xxx
# ifconfig enX up

# ifconfig enX down
# ifconfig enX detach
# chdev -l entX -a use_alt_addr=no
# chdev -l entX -a alt_addr=0x00000000000

This is a short procedure how to creat an AIX DVD from a base set of 8 AIX 5.3 CD's:

1. Copy all CD's using "cp -hRp" to a directory, start with the last CD and work towards the first one. You can do this on either an AIX or a Linux system.
2. Check that <directory>/installp/ppc contails all install images.
3. If not already, remove <directory>/usr/sys/inst.images. This directory also might contain all installation images.
4. Create a link <directory>/usr/sys/inst.images pointing to <directory>/installp/ppc.
5. Find all .toc files in the directory structure and, if necessary, change all vol%# entries to vol%1 (There should be at least 2 .toc files that need these updates). You have to change vol%2 to vol%1, vol%3 to vol%1, etcetera, up till vol%8.
6. Create an ISO image with RockRidge extentions:

   # mkisofs -R -o  
   

# lsdev -Cc cdrom
cd0 Available 3F-09-00-0,0 SCSI DVD-RAM Drive
cd1 Available 3F-09-00-5,0 16 Bit LVD SCSI DVD-ROM Drive

# lscfg -vl cd0
cd0  U1.9-P2-I1/Z2-A0  SCSI DVD-RAM Drive (4700 MB)
        Manufacturer................IBM
        Machine Type and Model......DVRM00203
        ROS Level and ID............A132
        Device Specific.(Z0)........058002028F000010
        Part Number.................04N5272
        EC Level....................F74471
        FRU Number..................04N5967

# rpm -ihv --ignoreos <filename>

# rpm -ihv --ignoreos /tmp/ibm-scsi-dvdram.dvrm00203-A151.rpm
ibm-scsi-dvdram.dvrm00203  #############################

# diag -d cd0 -c -T "download -s /etc/microcode -f"

# diag -d cd0 -c -T "download -s /etc/microcode -f"
Installation of the microcode has completed successfully.
The current microcode for cd0 is IBM-DVRM00203.A151.
Please run diagnostics on the device to ensure that it is
functioning properly.

# /usr/sbin/burn_cd -d /dev/cd0 /install/aix53ml4dvd.iso

Permanently change hostname for inet0 device in the ODM by choosing one of the following:

Command line method:

# chdev -l inet0 -a hostname=[newhostname]

# smitty hostname

# uname -S [newhostname]

# /etc/rc.net

# hostname [newhostname]

A very easy way to see what was installed recently on your system:

# lslpp -h

When you encounter an issue where ssh through a firewall works perfectly, but when doing scp of large files (for example mksysb images) the scp connection stalls, then there's a solution to this problem: Add "-l 8192" to the scp command.

The reason for scp to stall, is because scp greedily grabs as much bandwith of the network as possible when it transfers files, any delay caused by the network switch of the firewall can easily make the TCP connection stalled.

Adding the option "-l 8192" limits the scp session bandwith up to 8192 Kbit/second, which seems to work safe and fast enough (up to 1 MB/second):

# scp -l 8192 SOURCE DESTINATION

By default, AIX will avoid logging duplicate errpt entries. You can see the default settings using smitty errdemon, which will be set to checking duplicate entries within a 10000 milliseconds time interval (10 seconds). Also, the default duplicate error maximum is set to 1000, so after 1000 duplicates, an additional entry will be made, depending on which is reached earlier, the duplicate time interval of 10 seconds or the duplicate error maximum.