AIX uninstall

Purpose: create ramdisk to be able to dd the running system, then shut it down when the files are already deleted from the disk(s).

Normally, you should either wipe the disks:

a) from the install CD's disk menu

b) from a (Linux) live CD

c) in another AIX (provided that you run at least a pv=clear to prevent the another system from recognizing the foreign rootvg)

d) physically when security/internal regulations demand it

But there are situations when the system must be just shut down and the disks must be cleared. For example, when you have no physical access to it...

First steps

Detach/delete datavg(s)

Delete users

Delete non-BOS filesystems, sysdump, etc

Unmirror rootvg, wipe freed mirror copy disks

Stop daemons

The desired state: system running on a single last disk with a minimum set of processes and filesystems

Creating a ramdisk

The mkramdisk command

Usage: mkramdisk [-u] Size[M|G]

Suffix 'M' to specify Size in Megabytes

Suffix 'G' to specify Size in Gigabytes

Default Size is in 512-byte blocks

-u Specifies that the ram disk that is created will not be pinned. (default = pinned)

Creation (1GB):

# mkramdisk 1024M

/dev/rramdisk0

Removal:

# rmramdisk /dev/rramdisk0

JFS2

# mkfs -V jfs2 -o log=INLINE /dev/ramdisk0

mkfs: destroy /dev/ramdisk0 (yes)? y

logform: Format inline log for  <y>?

File system created successfully.

1040148 kilobytes total disk space.

Device /dev/ramdisk0:

  Standard empty filesystem

  Size:           2080296 512-byte (DEVBLKSIZE) blocks

# mount -olog=INLINE /dev/ramdisk0 /ram

JFS

# mkfs -V jfs /dev/ramdisk0

mkfs: destroy /dev/ramdisk0 (yes)? y

Device /dev/ramdisk0:

  Standard empty filesystem

  Size:           2097152 512-byte (UBSIZE) blocks

  Initial Inodes: 262144

# mount -V jfs -o nointegrity /dev/ramdisk0 /ram

# df -Ig /ram

Filesystem    GB blocks      Used      Free %Used Mounted on

/dev/ramdisk0      1.00      0.03      0.97    4% /ram

Errors, mistakes

# mount /dev/ramdisk0 /ram

mount: 0506-322 Cannot determine log device to use for /dev/ramdisk0 (/ram).

- You didn't specify -V jfs (JFS) or -olog=INLINE (JFS2).

# mount -olog=INLINE /dev/ramdisk0 /ram

Replaying log for /dev/ramdisk0.

Failure replaying log: -8

mount: 0506-324 Cannot mount /dev/ramdisk0 on /ram: The media is not formatted or the format is not correct.

- JFS doesn't support inline log.

# mount /dev/rramdisk0 /ram

mount: 0506-324 Cannot mount /dev/rramdisk0 on /ram: A system call received a parameter that is not valid.

- You shouldn't use the raw device for the file system commands (mkfs or mount)

The chroot environment

mkdir -p /ram/usr/bin /ram/usr/sbin /ram/usr/lib

cp /usr/sbin/halt /ram/usr/sbin

cp /usr/bin/ksh /ram/usr/bin

cp /usr/lib/libc.a /ram/usr/lib

cp /usr/lib/libcrypt.a /ram/usr/lib

## kernel

ls -l /unix

mkdir -p /ram/usr/lib/boot

cp /usr/lib/boot/unix_64 /ram/usr/lib/boot/unix

cp /usr/lib/boot/unix_64 /ram/unix

## test

chroot /ram /usr/bin/ksh

cp /usr/bin/find /ram/usr/bin

cp /usr/bin/ldd /ram/usr/bin

## why ldd oesn't work inside the chroot?

head -1 /ram/usr/bin/ldd

vi /ram/usr/bin/ldd

## #!/bin/ksh -> #!/usr/bin/ksh

## It isn't very important, as ldd needs a ton of textproc and other binaries...

## devices

mkdir /ram/dev

cd /ram/dev

mknod null c 2 2

mknod console c 4 0

chroot /ram /usr/bin/ksh

mkdir /ram/tmp

Deleting the last rootvg disk

# bootlist -m normal ent0

# bootlist -m normal -o

ent0

# chpv -c hdisk0

# cp /usr/bin/cat /ram/usr/bin

# cat > dd.sh

dd if=/dev/zero of=/dev/rhdisk0 bs=1m 2>&1 > /ram/RESULT

# nohup sh ./dd.sh &

[1] 184534

# chroot /ram /usr/bin/ksh

# echo *

FILE RESULT dd.sh dev lost+found nohup.out tmp unix usr

# cat RESULT

# find RESULT -ls

21 0 -rw-r--r-- 1 0 3 0 Oct 10 15:07 RESULT

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