Advanced administration and problem determination

Advanced Administration
And
Problem Determination
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2
Advanced Administration And
목차
1. The Object Data Manager
2. Error monitoring
3. System initializing
4. Disk management

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What is the ODM?
-The Object Data Manager (ODM) is a database
intended for storing system information.
-Physical and logical device information is stored and
maintained through the use of object with associated
characteristics.

5
Data managed by the ODM
ODM
Devices
System
Resource
controller
TCP/IP
configurati
on
Error Log,
Dump
NIM
SMIT
menus
Software

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System data managed by ODM
-The ODM manages the following system data:
-Device configuration data
-Software Vital Product Data (SWVPD)
-System Resource Controller (SRC) data
-TCP/IP configuration data
-Error log and dump information
-NIM (Network Installation Manager) information
-SMIT menus and commands

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ODM database files
PdDv - predefined device
PdAt - predefined Attribute
PdCn - predefined connection
CuDv - Customized device
CuAt - Customized Attribute
CuVPD - Customized vital Product data
CuDvDr -Customized Device Driver
CuDep - Customized dependency
Config_rules - 디바이스 잡는 순서
Predefined device information PdDv, PdAt, PdCn
Customized device information CuDv, CuAt, CuDep, CuDvDr,
CuVPD, Config_Rules

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Device configuration summary
Configuration
Manager
(cfgmgr)
PdCn
CuDep
CuDvDr
CuDv
Config_Rule
s
PdAtPdDv
CuAt
CuVPD
Predefined database
Customized database

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Roles of cfgmgr and Config_Rules
When an AIX system boots, the Configuration Manager
(cfgmgr) is responsible for configuring devices.
There is one ODM object class which the cfgmgr uses
to determine the correct sequence when configuring
devices: Config_Rules.
This ODM object class also contains information about
various methods files used for device management.

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Data not managed by ODM
-Filesystem information : /etc/filesystems
-User/security information : /etc/security/user
-Queues and queue devices : /etc/qconfig

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Changing attribute values
#odmget –q”uniquetype=tape/scsi/scsd and attribute=block_size” PdAt > file
#vi file
PdAt :
uniquetype = “tape/scsi/scsd”
attribute = “block_size”
deflt = “512”
values = “0-2147483648,1”
width = “ “
type = “R”
#odmdelete –o PdAt –q”uniquetype=tape/scsi/scsd and attribute=block_size”
#odmadd file
Modify deflt to 512

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Using odmchange to change attribute values
#odmget –q”uniquetype=tape/scsi/scsd and attribute=block_size” PdAt > file
#vi file
PdAt :
deflt = “512”
values = “0-2147483648,1”
width = “ “
type = “R”
#odmchange –o PdAt –q”uniquetype=tape/scsi/scsd and attribute=block_size” file
Modify deflt to 512

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Predefined devices (PdDv)
PdDv :
type = “scsd”
class = “tape”
subclass = “scsi”
prefix = “rmt”
…
base = 0
detectable = 1
…
led = 2418
setno = 54
msgno = 0
catalog = “devices.cat”
…

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Predefined devices (PdDv)
base =
This descriptor specifies whether a device is a base device or not.
A base device is any device that forms part of a minimal base system.
During system boot, a minimal base system is configured to permit access
to the root volume group and hence to the root file system.
detectable =
This specifies whether the device instance is detectable of undetectable.
A device whose presence and type can be determined by the cfgmgr, once
it is actually powered on and attached to the system, is said to be detectable

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Predefined attributes (PdAt)
PdAt :
deflt = “ “
values = “0-2147483648,1”
…
PdAt :
uniquetype = “disk/scsi/osdisk”
attribute = “pvid”
deflt = “none”
values = “ “
…
PdAt :
uniquetype = “tty/rs232/tty”
attribute = “term”
deflt = “dumb”
values = “ “
…

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Predefined attributes (PdAt)
attribute =
This identifies the name of the attribute. This is the name that can be passed to
the mkdev or chdev command. For example, to change the default name of
dump to ibm3151 for tty0, you can issue the following command:
# chdev –l tty0 –a term=ibm3151
values =
This identifies the possible values that can be associated with the attribute name.
For example, allowed values for the block_size attribute range from 0 to 2147483648,
with an increment of 1

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Customized devices (CuDv)
CuDv :
name = “ent1”
status = 1
chgstatus = 2
ddins = “pci/goentdd”
location = “02-08”
parent = “pci2”
connwhere = “8”
PdDvLn = “adapter/pci/14106902”
CuDv :
name = “hdisk2”
status = 1
chgstatus = 2
ddins = “scdisk”
location = “01-08-01-8,0”
parent = “scsi1”
connwhere = “8,0”
PdDvLn = “disk/scsi/scsd”

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Customized devices (CuDv)
Status
This identifies the current status of the device instance. Possible values are :
- status = 0 (Defined)
- status = 1 (Available)
- status = 2 (Stopped)
Chgstatus
This flag tells whether the device instance has been altered since the last system boot.
The diagnostics facility uses this flag to validate system configuration.
The flag can take these values :
- chgstatus = 0 (New device)
- chgstatus = 1 (Don’t care)
- chgstatus = 2 (Same)
- chgstatus = 3 (Device is missing)

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Customized attributes (CuAt)
CuAt :
name = “ent1”
attribute = “humbo_frames”
value = “yes”
…
CuAt :
name = “hdisk2”
attribute = “pvid”
value = “00c35ba0816eafe50000000000000000”
…

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2. Error mornitoring
#errpt

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#errpt -A

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A summary report
Error types
Valid error types include the following :
- PEND – The loss of availability of a device or component is imminent.
- PERF – The performance of the device or component has degraded to below
an acceptable level.
- TEMP – Recovered from condition after several attempts.
- PERM – Unable to recover from error condition. Error types with this value are
usually the most severe errors and imply that you have a hardware or
software defect. Error types other than PERM usually do not indicate a
defect, but they are recorded so that they can be analyzed by the
diagnostic programs.
- UNKN – Severity of the error cannot be determined.
- INFO – The error type is used to record informational entries.
Error Classes
H (hardware), S (software), O (operator), U (Undetermined).

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The errpt command
- Summary report :
#errpt
- Detailed report :
#errpt –a
-Summary report of all hardware errors :
#errpt –d H
-Detailed report of all software errors :
#errpt –a –d S
-Concurrent error logging(“Real-time” error logging) :
#errpt –c > /dev/console

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Types of Disk Errors
* error types : P=permanent
T=temporary
Error Label Error Type Recommendation
DISK_ERR1 P Failure of physical volume media
Action:Replace device as soon as possible
DISK_ERR2,
DISK_ERR3
P Device does not response
Action:Check power supply
DISK_ERR4 T Error cause by bad block or occurrence of a
recover error
Rule of thump:if disk produces more than one
DISK_ERR4 per week, replace the disk.
SCSI_ERR* P SCSI communication problem
Action:Check cable, SCSI addresses, terminator

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LVM Error Log Entries
* error class : H=hardware
Error Classes : H = hardware Error Types : P = permanent
S= software T = Temporary
Error Label Class & Type Recommendations
LVM_BBEPOOL,
LVM_BBERELMAX,
LVM_HWFAIL
S,P NO more bad block relocation.
Action:Replace disk as soon as
possible
LVM_SA_STALEPP S,P Stale physical partition.
Action:Check disk, Synchronize data
(syncvg)
LVM_SA_QUORCLOS
E
H,P Qourom lost, volume group closing.
Action:Check disk, consider working
without quorom.

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Maintaining the error log
#smit errdemon
#smit errclear

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Self-made error notification
#! /usr/bin/ksh
errpt > /tmp/errlog.1
while true
do
sleep 60
#compare the two files.
#If no difference, let’s sleep again
cmp –s /tmp/errlog.1 /tmp/errlog.2 && continue
#files are different : Let’s inform the operator :
print “Operator : check error log” > /dev/console
done

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syslogd configuration examples
/etc/syslogd.conf :
auth.debug /dev/console
mail.debug /tmp/mail.debug
daemon.debug /tmp/daemon.debug
*.debug; mail.none @server
After changing /etc/syslog.conf :
# refresh –s syslogd
All security messages to the system
console
collect all mail messages in
/tmp/mail.debug
collect all daemon messages in
/tmp/daemon.debug
Send all messages, except mail
messages, to host server

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Redirecting syslog messages to error log
/etc/syslogd.conf :
*.debug errorlog
# errpt
IDENTIFIER TIMESTAMP T C RESOURCE_NAME DESCRIPTION
...
C6ACA566 0505071399 U S syslog MESSAGE REDIRECTED FROM SYSLOG
...
Redirect all syslog
messages to error log

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3. System initialization
How does a System p server or LPAR boot?
Check and initialize
the hardware
POST.
Locate boot image
using the boot list.
Load and pass control
to boot image.
Start AIX software
initialization.
Possible failures
Hardware error.
Unable to find any boot image.
Boot image corrupted.

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Loading of a boot image
Firmware
boot deivces :
(1)diskette
(2)CD-Rom
(3)Internal disk
(4)Network
Boot controller
RAM
Bootstrap code
Boot Logical
Volume(hd5)
hdisk0
Bootstrap code :
System p and pSeries systems can manage several different operation systems.
The hardware is not bound to the software. The first block of the boot disk contains
bootstrap code that is loaded into RAM during the boot process. This part is sometimes
referred to as System Read Only Storage(ROS). The bootstrap code gets control.
The task of this code is to locate the boot logical volume on the disk, and load the boot
image. In some technical manuals, this second part is called the Software ROS.

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Contents of the boot logical volume (hd5)
AIX Kernel RAMFS Reduced ODM
AIX Kernel :
The AIX kernel is the core of the operating system and provides basic services like
process, memory, and device management. The AIX kernel is always loaded from the
boot logical volume. There is a copy of the AIX kernel in the hd4 file system (under the
name /unix), but this program has no role in system initialization. Never remove /unix,
because it is used for rebuilding the kernel in the boot logical volume.
RAMFS :
This RAMFS is a reduced or miniature root file system which is loaded into memory and
used as if it were a disk-based file system. The contents of the RAMFS are slightly
different depending on the type of system boot.
Reduced ODM :
The boot logical volume contains a reduced copy of the ODM. During the boot process,
many devices are configured before hd4 is available. For these devices, the
corresponding ODM files must be stored in the boot logical volume.

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Unable to find boot image (Working with bootlists)
Normal bootlist :
# bootlist –m normal hdisk0 hdisk1
# bootlist –m normal –o
hdisk0 blv=hd5
hdisk1 blv=hd5
Customization service bootlist :
# bootlist –m service –o
cd0
hdisk0 blv=hd5
ent0
Service bootlist – over network :
# bootlist –m service ent0 gateway=192.168.1.1
bserver=192.168.1.3 client=192.168.1.57

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Starting System Management Services (SMS mode)
Reboot or power on the system
Press F1 and enter the SMS mode
Select Boot Options
Configure Boot Device Order
Select 1st
Boot Device
List All Devices

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Accessing a system that will not boot
Boot the system from
the BOS CD-ROM, tape or
network device(NIM)
Select maintenance mode
Perform corrective actions
Recover data
Maintenance
1. Access a Root Volume Group
2. Copy a System Dump to Media
3. Access Advanced Maintenance
4. Install from a System Backup

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How to fix a corrupted BLV (Boot Logical Volume)
Maintenance Mode
Access a Root Volume Group
# bosboot –ad /dev/hdisk0
# shutdown -Fr
Rebuild BLV
Maintenance mode
If the boot logical volume is corrupted (for example, bad blocks on a disk might cause a
corrupted BLV), the machine will not boot.
To fix this situation, you must boot your machine in maintenance mode, from a CD or
tape. If NIM has been set up for a machine, you can also boot the machine from a NIM
master in maintenance mode. NIM is actually a common way to do special boots in a
logical partition environment.

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How to fix a corrupted BLV (Boot Logical Volume)
Recreating the boot logical volume
1.Boot your machine in maintenance mode (from CD or tape) to access the Systems
Management Services (SMS) to select the boot device.
2. Remove the old hd5 logical volume.
# rmlv hd5
3. Clear the boot record at the beginning of the disk.
# chpv –c hdisk0
4. Create a new hd5 logical volume : one physical partition in size, it must be in rootvg
and outer edge as intrapolicy. Specify boot as the logical volume type.
# mklv –y hd5 –t boot –a e rootvg 1
5. Run the bosboot command as described on the visual.
# bosboot –ad /dev/hdisk0
6. Check the actual bootlist and reboot the system
# bootlist –m normal –o
# sync;sync;shutdown -Fr

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System software initialization overview
Load kernel and pass control
Restore RAM file system
from boot image
Start init process
(from RAMFS)
Start “real” init process
(from rootvg)
rc.boot 1
rc.boot 2
rc.boot 3
/
etc,dev,mnt,usr
/etc/inittab
Configure base
devices
Active rootvg
Configure
remaining devices

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Boot sequence
The visual shows the boot sequence after loading the AIX kernel from the boot image
1.The kernel restores a RAM file system into memory by using information provided in
the boot image. At this stage the rootvg is not available, so the kernel needs to work
with commands provided in the RAM file system. You can consider this RAM file system as a
small AIX operating system.
2.The kernel starts the init process which was provided in the RAM file system (not from the
root file system). This init process executes a boot script rc.boot.
2.rc.boot controls the boot process. In the first phase (it is called by init with rc.boot 1), the
base devices are configured. In the second phase (rc.boot 2), the rootvg is activated (or
varied on).
4.After activating the rootvg at the end of rc.boot 2, the kernel overmounts the RAM file
system with the file systems from rootvg. The init from the boot image is replaced by the init
from the root file system, hd4.
5. This init processes the /etc/inittab file. Out of this file, rc.boot is called a third time(rc.boot
3) and all remaining devices are configured.

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rc.boot 1
Process 1
init
rc.boot 1
restbase
cfgmgr –f
Boot image
ODM
RAM file syetem
ODM
rootvg is not
active.
bootinfo -b
Devices to
activate rootvg
are configured!!
Confie_Rules
phase=1
F05
510
511
c06
548
Failure LED

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rc.boot phase 1 actions
The init process started from the RAM file system, executes the boot script rc.boot 1. If init
fails for some reason(for example, a bad boot logical volume), c06 is shown on the LED
display. The following steps are executed when rc.boot 1 is called:
1.The restbase command is called which copies the ODM from the boot image into the RAM
file system. After this step, an ODM is available in the RAM file system. The LED shows 510
if restbase completes successfully, otherwise LED 548 is shown.
2.When the restbase has completed successfully, the configuration manager(cfgmgr) is run
with the option –f (first). cfgmgr reads the Config_Rules class and executes all methods that
stored under phase=1. Phase 1 configuration methods result in the configuration of base
devices into the system, so that the rootvg can be activated in the next rc.boot phase.

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3. Base devices are all devices that are necessary to access the rootvg. If the rootvg is
stored on hdisk0, all devices from the mother board to the disk itself must be configured in
order to be able to access the rootvg.
4.At the end of rc.boot 1, the system determines the last boot device by calling bootinfo –b.
The LED shows 511.

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rc.boot 2 (part 1)
rc.boot2
ipl_varyon
fsck –f /dev/hd4
mount /dev/hd4
fsck –f /dev/hd2
mount /usr
fsck –f /dev/hd9var
mount /var
copycore
umount /var
551
517
511c06
556
Failure LED
swapon /dev/hd6
555
557
518
518
hd4:
/
hd2:
/usr
hd9var
:
/var
hd6
rootvg
/
RAM file system
varusrmntetcdev
copycore:
if dump,
copy

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rc.boot phase 2 actions (part 1)
rc.boot is run for the second time and is passed the parameter 2. The LED shows 551.
The following steps take part in this boot phase :
1.The rootvg is varied on with a special version of the varyonvg command designed to
handle rootvg. If ipl_varyon completes successfully, 517 is shown on the LED, otherwise
552,552 or 556 are shown and the boot process stops.
1.The root file system, hd4, is checked by fsck. The option –f means that the file system is
checked only if it was not unmounted cleanly during the last shutdown. This improves the
boot performance. If the check fails, LED 555 is shown.
1.Afterwards, /dev/hd4 is mounted directly onto the root in the RAM file system. If the mount
fails, for example due to a corrupted JFS log, the LED 557 is shown and the boot process
stops.

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4. Next, /dev/hd2 is checked and mounted (again with option –f, it is checked only if the file
system wasn’t unmounted cleanly). If the mount fails, LED 518 is displayed and the boot
stops.
5.Next, the /var file system is checked and mounted. This is necessary at this stage, because
the copycore command checks if a dump occurred. If a dump exits in a paging space device,
it will be copied from the dump device, /dev/hd6, to the copy directory which is by default the
directory /var/adm/ras. /var is unmounted afterwards.
5.The primary paging space /dev/hd6 is made available.

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rc.boot 2 (part 2)
swapon /dev/hd6
Copy RAM /dev files to disk :
mergydev
Copy RAM ODM files to disk :
cp /../etc/objrepos/Cu*
/etc/objrepos
mount /var
Copy boot messages to alog
Kernel removes RAMFS
hd4:
/
hd2:
/usr
hd9var
:
/var
hd6
rootvg
/
RAM file system
varusrmnt
etc
ODM
dev
dev
etc
ODM

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After the paging space /dev/hd6 has been made available, the following tasks are executed
in rc.boot 2 :
1.To understand this steps, remember two things :
- /dev/hd4 is mounted onto root in the RAM file system.
- In rc.boot 1, the cfgmgr has been called and all base devices are configured. This
configuration data has been written into the ODM of the RAM file system.
Now, mergedev is called and all /dev files from the RAM file system are copied to disk.
2.All customized ODM files from the RAM file system ODM are copied to disk as well. At this
stage, both ODMs (in hd5 and hd4) are in sync now.

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3. The /var/file system (hd9var) is mounted
4. All messages during the boot process are copied into a special file. You must use the
alog command to view this file :
# alog –t boot –o
As no console is available at this stage all boot information is collected in this file.
When rc.boot 2 is finished, the /, usr, and /var file system in rootvg are active.
Final stage
At this stage, the AIX kernel removes the RAM file system (returns the memory to the free
memory pool) and starts the init process from the / file system in rootvg.

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rc.boot 3 (part 1)
/etc/inittab :
/sbin/rc.boot 3
fsck –f /dev/hd3
mount /tmp
syncvg rootvg &
Normal : cfgmgr –p2
Service : cfgmgr –p3
cfgcon
rc.dt boot
savebase
551
551
551
551
Process 1
init
Here, we
work with
Rootvg.
517
553
/etc/objrepos :
ODM
hd5 :
ODM
Config_Rules
phase=2
phase=3

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At this boot stage, the /etc/init process is started. It reads the /etc/inittab file (LED 553 is
displayed) and executes the commands line-by-line. It runs rc.boot for the third time, passing
the argument 3 that indicates the last boot phase.
rc.boot 3 executes the following tasks :
1.The /tmp file system is checked and mounted.
1.The rootvg is synchronized by syncvg rootvg. If rootvg contains any stale partitions (for
example, a disk that is part of rootvg was not active), these partitions are updated and
synchronized. syncvg is started as background job.
1.The configuration manager is called again. If the key switch or boot mode is normal, the
cfgmgr is called with option –p2 (phase 2). If the key switch or boot mode is service, the
cfgmgr is called with option –p3 (phase 3).

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4.The configuration manager reads the ODM class Config_Rules and executes either all
methods for phase=2 or phase=3. All remaining devices that are not base devices are
configured in this step.
4.The console will be configured by cfgcon. The numbers c31, c32, c33 or c34 are displayed
depending on the type of console :
- c31 : Console not yet configured. Provides instruction to select a console.
- c32 : console is lft terminal.
- c33 : console is tty.
- c34 : console is a file on the disk.
If CDE is specified in /etc/inittab, the CDE will be started and you get a graphical boot on
the console.
6.To synchronize the ODM in the boot logical volume with the ODM from the / file system,
savebase is called.

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rc.boot 3 (part 2)
savebase
syncd 60
errdemon
Turn off LEDs
rm /etc/nologin
chgstatus=3
CuDv ?
Execute next line in
/etc/inittab
/etc/objrepos :
ODM
hd5 :
ODM
A device that was previously detected
could not be found. Run “diag –a”.
System initialization is completed.
Yes

55
After the ODMs have been synchronize again, the following steps take place :
1.The syncd daemon is started. All data that is written to disk is first stored in a cache in
memory before writing it to the disk. The syncd daemon writes the data from the cache each
60 second to the disk
1.The LED displayed is turn off.
1.If the file /etc/nologin exists, it will be removed. If a system administrator creates this file, a
login to the AIX machine is not possible. During the boot process /etc/nologin will be
removed.
1.If devices exists that are flagged as missing in CuDv (chgstatus=3), a message is
displayed on the console. For example, this could happen if external devices are not
powered on during system boot.
1.The last message, System initialization completed, is written to the console. rc.boot 3 is
finished. The init process executes the next command in /etc/inittab.

56
Fixing corrupted file systems and logs
-Boot to maintenance mode
-Access rootvg without mounting file systems
-Rebuild file system log and run fsck :
# logform –V jfs2 /dev/hd8
# fsck –y –V jfs2 /dev/hd1
# fsck –y –V jfs2 /dev/hd9var
# fsck –y –V jfs2 /dev/hd10opt
# fsck –y –V jfs2 /dev/hd11admin

57
/etc/inittab file
init:2:initdefault:
brc::sysinit:/sbin/rc.boot 3 >/dev/console 2>&1 # Phase 3 of system boot
powerfail::powerfail:/etc/rc.powerfail 2>&1 | alog -tboot > /dev/console # Power Failure Detection
mkatmpvc:2:once:/usr/sbin/mkatmpvc >/dev/console 2>&1
atmsvcd:2:once:/usr/sbin/atmsvcd >/dev/console 2>&1
tunables:23456789:wait:/usr/sbin/tunrestore -R > /dev/console 2>&1 # Set tunables
securityboot:2:bootwait:/etc/rc.security.boot > /dev/console 2>&1
rc:23456789:wait:/etc/rc 2>&1 | alog -tboot > /dev/console # Multi-User checks
fbcheck:23456789:wait:/usr/sbin/fbcheck 2>&1 | alog -tboot > /dev/console # run /etc/firstboot
srcmstr:23456789:respawn:/usr/sbin/srcmstr # System Resource Controller
platform_agent:2:once:/usr/bin/startsrc -s platform_agent >/dev/null 2>&1
rctcpip:23456789:wait:/etc/rc.tcpip > /dev/console 2>&1 # Start TCP/IP daemons
sniinst:2:wait:/var/adm/sni/sniprei > /dev/console 2>&1
rcnfs:23456789:wait:/etc/rc.nfs > /dev/console 2>&1 # Start NFS Daemons
cron:23456789:respawn:/usr/sbin/cron
piobe:2:wait:/usr/lib/lpd/pioinit_cp >/dev/null 2>&1 # pb cleanup
qdaemon:23456789:wait:/usr/bin/startsrc -sqdaemon
writesrv:23456789:wait:/usr/bin/startsrc -swritesrv
uprintfd:23456789:respawn:/usr/sbin/uprintfd
shdaemon:2:off:/usr/sbin/shdaemon >/dev/console 2>&1 # High availability daemon
Do not use an editor to change /etc/inittab.
Use mkitab, chitab, rmitab instead.

58
Modifying /etc/inittab
Do not use an editor to change the /etc/inittab file. One small mistaken in /etc/inittab, and
your machine will not boot. Instead use the command mkitab, chitab, and rmitab to edit
/etc/inittab.
Consider the following examples :
-To add a line to /etc/inittab, use the mkitab command. For example :
# mkitab “myid:2:once:/usr/local/bin/errlog.check”
-To change /etc/inittab so that init will ignor the line tty1, use the chitab command :
# chitab “tty1:2:off:/usr/sbin/getty /dev/tty1”
-To remove the line tty1 from /etc/inittab, use the rmitab command. For example :
# rmitab tty1
Viewing /etc/inittab
The lsitab command can be used to view /etc/inittab file. For example :
# lsitab dt
dt:2:wait:/etc/rc.dt
If you issue lsitab –a, the complete /etc/inittab file is shown.

59
Boot problem management
Check LED User action
Bootlist wrong? LED codes cycle Power on, press F1, select Multi-Boot, select the correct boot device.
/etc/inittab corrupt?
/etc/environment corrupt?
553 Access the rootvg. Check /etc/inittab (empty, missing or corrupt).
Check /etc/environment.
Boot logical volume or
Boot record corrupt?
20EE000B Access the rootvg. Re-create the BLV :
# bosboot –ad /dev/hdiskXX
JFS / JFS2 log corrupt? 551,552,554,555,556,557 Access rootvg before mounting the rootvg file systems.
Re-create the JFS / JFS2 log:
#logform –V jfs /dev/hd8 or
#logform –V jfs2 /dev/hd8
Run fsck afterwards.
Superblock corrupt? 552.554.556 Run fsck against all rootvg file system. If fsck indicates errors (not an
AIX file system), repair the superblock as described in the notes.
rootvg locked? 551 Access rootvg and unlock the rootvg :
# chvg –u rootvg
ODM files missing? 523 – 534 ODM files are missing or inaccesible. Restore the missing files from a
system backup
Mount of /usr or /var failed? 518 Check /etc/filesystems. Check network (remote mount), file systems
(fsck) and hardware.

60
Notes:
Superblock corrupt?
Another thing you can try is to check the superblocks of your rootvg file systems. If you boot
maintenance mode and you get error messages like Not an AIX file system or Not a
recognized file type, it is probably due to a corrupt superblock in the file system.
Each file system has two super blocks. Executing fsck should automatically recover the
primary superblock by copying from the backup superblock. The following is provided in case
you need to do this manually
For JFS, the primary superblock is in logical block 1 and copy is in logical block 31. To
manually copy the superblock from block 31 to block 1 for the root file system(in this
example), issue the following command :
# dd count=1 bs=4k skip=31 seek=1 if=/dev/hd4 of=/dev/hd4
For JFS2, the locations are different. To manually recover the primary superblock from the
backup superblock for the root file system(in this example), issue the following command :
# dd count=1 bs=4k skip=15 seek=8 if=/dev/hd4 of=/dev/hd4

61
Notes:
rootvg locked?
Many LVM commands place a lock into the ODM to prevent other commands from working at
the same time. If a lock remains in the ODM due to a crash of a command, this may lead to a
hanging system.
To unlock the rootvg, boot in maintenance mode and access the rootvg with file systems.
Issue the following command to unlock the rootvg:
# chvg –u rootvg
Mount of /usr of /var failed?
An LED of 518 indicates that the mount of the /usr or /var file system failed. If /usr is mounted
from a network, check the network connection. If /usr or /var are locally mounted, use fsck to
check the consistency of the file systems. If this does not help, check the hardware by
running diagnostics from the Diagnostic CD.

63
4. Disk management
The logical volume control block (LVCB)
# getlvcb -AT hd2
AIX LVCB
intrapolicy = c
copies = 1
interpolicy = m
lvid = 00c1f0c500004c000000012fc86327fb.5
lvname = hd2
label = /usr
machine id = 1F0C54C00
number lps = 10
relocatable = y
strict = y
stripe width = 0
stripe size in exponent = 0
type = jfs2
upperbound = 32
fs =
time created = Sat May 7 02:58:16 2011
time modified = Tue May 31 03:39:59 2011

64
4. Disk management
Notes:
The LVCB and the getlvcb command
The LVCB stores attributes of a logical volume. The getlvcb command queries an LVCB.
Example on visual
In the example on the visual, the getlvcb command is used to obtain information from the
logical volume hd2. The information displayed includes the following :
-Intrapolicy
-Number of copies (1=No mirroring)
-Interpolicy
-Number of logical partition (10)
-Can the partitions be reorganized? (relocatable = y)

65
4. Disk management
How LVM interacts with ODM and VGDA
VGDA
LVCB
mkvg
extendvg
mklv
crfs
chfs
rmlv
reducevg
...
...
ODM
/etc/filesystems
remove
importvg
exportvg
Change, using
low-level
command
Match IDs by name
Update

66
4. Disk management
Notes:
High-level commands
Most of the LVM commands that are used when working with volume groups, physical, or
logical volumes are high-level commands. These high-level commands (like mkvg, extendvg,
mklv and others listed on the visual) are implemented as shell scripts and use names to
reference a certain LVM object. The ODM is consulted to match a name, for example, rootvg
or hdisk0, to an identifier.
Interaction with disk control blocks and the ODM
The high-level commands call intermediate or low-level commands that query or change the
disk control blocks VGDA or LVCB. Additionally, the ODM has to be updated; for example, to
add a new logical volume. The high-level commands contain signal handlers to clean up the
configuration if the program is stopped abnormally. If a system crashes, or if high-level
commands are stopped by kill -9, the system can end up in a situation where the
VGDA/LVCB and the ODM are not in sync. The same situation may occur when low-level
commands are used incorrectly.

67
4. Disk management
Notes:
The importvg and exportvg commands
The command importvg imports a complete new volume group based on a VGDA and LVCB
on a disk. The command exportvg removes a complete volume group from the ODM.
VGDA and LVCB corruption
The focus in this course is on situation where the ODM is corrupted and we assume that the
LVM control data (for example, the VGDA or the LVCB) are correct. If an attempted
execution of LVM commands (for example: lsvg, varyonvg, reducevg) results in a failure with
core dump, that could be an indication that the LVM control data on one of the disk has
become corrupted. In this situation, do not attempted to resync the ODM using the
procedures covered. In most cases, you will need to recover from a volume group backup. If
recovery from backup is not a viable option, It is suggested that you work with AIX Support in
dealing with the problem. Attempting to use the procedures covered In this unit will not solve
the problem. Even worse, you will likely propagate the corruption to other disks in the volume
group, thus making the situation even worse.

68
4. Disk management
ODM-related LVM problems
What can cause problems?
-kill -9, shutdown, system crash
-Improper use of low-level commands
-Hardware changes without or with wrong software actions
-Full root file system
Normal functioning of high-level commands
As already mentioned, most of the time administrators use high-level commands to create
or update volume groups or logical volumes. These commands use signal handlers to set
up a proper cleanup in case of an interruption. Additionally, LVM commands use a locking
mechanism to block other commands while a change is in progress.
Causes of problems
The signal handlers used by high-level LVM commands do not work with a kill -9, a system
shutdown, or system crash. You might end up in a situation where the VGDA has been
updated, but the change has not been stored in the ODM
Problems might also occur because of the improper use of low-level commands or
hardware changes that are not followed by correct administrator actions.
Another common problems is ODM corruption when performing LVM operation when the
root file system (which contains /etc/objrepos) is full.

69
4. Disk management
Fixing ODM problems (1 of 2)
If the ODM problem is not in the rootvg, for example in volume group homevg, do the
Following :
# varyoffvg homevg
# exportvg homevg (remove complete volume group from the ODM)
#importvg –y homevg hdiskXX (Import volume group and create new ODM objects)
Steps in ODM repair procedure (for problem not in rootvg)
1.In the first step, you vary off the volume group, which requires that all file systems be
unmounted first. To vary off a volume group, use the varyoffvg command.
1.In the next step, you export the volume group by using the exportvg command. This
command removes the complete volume group from the ODM. The VGDA and LVCB are not
touched by exportvg.
1.In the last step, you import the volume group by using the importvg command. Specify the
volume group name with option –y, otherwise AIX creates a new volume group name.
You need to specify only one intact physical volume of the volume group that you import.
The importvg command reads the VGDA and LVCB on that disk and creates completely new
ODM objects.

70
4. Disk management
Fixing ODM problems (2 of 2)
If the ODM problem is in the rootvg, try using the rvgrecover procedure :
PV=hdisk0
VG=rootvg
cp /etc/objrepos/CuAt /etc/objrepos/CuAt.$$
cp /etc/objrepos/CuDep /etc/objrepos/CuDep.$$
cp /etc/objrepos/CuDv /etc/objrepos/CuDv.$$
cp /etc/objrepos/CuDvDr /etc/objrepos/CuDvDr.$$
lqueryvg –Lp $PV | awk ‘{print $2}’ | while read LVname;
do
odmdelete –q “name=$LVname” –o CuAt
odmdelete –q “name=$LVname” –o CuDv
odmdelete –q “value3=$LVname” –o CuDvDr
done
odmdelete –q “name=$VG” –o CuAt
odmdelete –q “parent=$VG” –o CuDv
odmdelete –q “name=$VG” –o CuDv
odmdelete –q “name=$VG” –o CuDep
odmdelete –q “dependency=$VG” –o CuDep
odmdelete –q “value1=10” –o CuDvDr
odmdelete –q “value3=$VG” –o CuDvDr
importvg -y $VG $PV #ignore lvaryoffvg errors
varyonvg $VG

71
4. Disk management
Notes:
Problems in rootvg
For ODM problems in rootvg, finding a solution is more difficult because rootvg cannot be
varied off or exported. However, it may be possible to fix the problem using one of the
techniques described below.
The rvgrecover procedure
If you detect ODM problems in rootvg, you can try using the procedure called rvgrecover.
You may want to code this in a script (shown on the visual) in /bin and mark it executable.
The rvgrecover procedure removes all ODM entries that belong to your rootvg by using
odmdelete. That is the same way exportvg works.
After deleting all ODM object from rootvg, it imports the rootvg by reading the VGDA and
LVCB from the boot disk. This results in completely new ODM object that describe your
rootvg.

72
4. Disk management
RAM disk maintenance mode (1 of 3)
With the rootvg, the corruption problem may prevent a normal boot to multiuser mode.
Thus, you may need to handle this situation in RAM Disk Maintenance Mode (boot into
Maintenance mode from the CD-ROM or NIM). Before attempting this, you shuold make sure
you have a current mksysb backup.
Use the steps in the following table (which are similar to those in the rvgrecover script shown
on the visual) to recover the rootvg volume group after booting to maintenance mode and file
system mounting.
1.Delete all of the ODM information about logical volumes.
Get the list of logical volumes from the VGDA of the physical volume.
# lqueryvg –p hdisk0 –L | awk ‘{print $2}’ | while read LVname; do
>odmdelete –q “name=$LVname” –o CuAt
>odmdelete –q “name=$LVname” –o CuDv
>odmdelete –q “value3=$LVname” –o CuDvDr
>done

73
4. Disk management
2. Delete the volume group information from ODM.
# odmdelete –q “name=rootvg” –o CuAt
# odmdelete –q “parent=rootvg” –o CuDv
# odmdelete –q “name=rootvg” –o CuDv
# odmdelete –q “name=rootvg” –o CuDep
# odmdelete –q “dependency=rootvg” –o CuDep
# odmdelete –q “value1=10” –o CuDvDr
# odmdelete –q “value3=rootvg” –o CuDvDr
3. Add the volume group associate with the physical volume back to the ODM.
# importvg –y rootvg hdisk0
4. Recreate the device configuration database in the ODM from the information on the
physical volume.
#varyonvg –f rootvg

74
4. Disk management
This assumes that hdisk0 is part of rootvg.
In CuDvDr :
value1 = major number
value2 = minor number
value3 = object name for major/minor number
rootvg always has value1 = 10.
The steps can also be used to recover other volume groups by substituting the appropriate
physical volume and volume group information. It is suggested that this example be made a
script.

75
4. Disk management
Disk replacement : Starting point
Disk
mirrored?
Disk still
working?
Volume
group
lost?
procedure 1
procedure 2
procedure 3
procedure 4 procedure 5
A disk must be replaced...
Yes
Yes
Yes
Yes
rootvg Not rootvg
No
No

76
4. Disk management
Procedure 1 : Disk mirrored
1. Remove all copies from disk :
# unmirrorvg vg_name hdiskX
2. Remove disk from volume group :
# reducevg vg_name hdiskX
3. Remove disk from ODM :
# rmdev –dl hdiskX
4. Connect new disk to system
May have to shutdown if not hot-pluggable
5. Add new disk to volume group :
# extendvg vg_name hdiskY
6. Create new copies :
# mirrorvg vg_name hdiskY
# syncvg vg_name

77
4. Disk management
Procedure 2 : Disk still working
1. Connect new disk to system.
# extendvg vg_name hdiskY
3. Migrate old disk to new disk :
# migratepv hdiskX hdiskY
4. Remove old disk from volume group
5. Remove old disk from ODM :

78
4. Disk management
Procedure 2 : Disk still working (special steps for rootvg)
1. Connect new disk to system.
3. Migrate old disk to new disk :
4. Remove old disk from volume group
5. Remove old disk from ODM :
3. Disk contains hd5?
# migratepv –l hd5 hdiskX hdiskY
# bosboot –ad /dev/hdiskY
# chpv –c hdiskX
# bootlist –m normal hdiskY
If the disk contains primary dump
device, you must deactivate the dump
device.
# sysdumpdev –p /dev/sysdumpnull
Migrate old disk to new disk :
# migratepv hdiskX hdiskY
After completing migration, you have
to activate dump device again.
# sysdumpdev –p /dev/hdX

79
4. Disk management
Procedure 3 : Disk in missing or removed state
1. Identify all LVs and file systems on failing disk :
# lspv –l hdiskY
2. Umount all file systems on failing disk :
# umount /dev/lv_name
3. Remove all file systems and LVs from failing disk :
# smit rmfs #rmlv lv_name
4. Remove disk from volume group
5. Remove old disk from system :
# extendvg vg_name hdiskZ
7. Recreate all LVs and file systems on new disk :
# mklv –y lv_name # smit crfs
8. Restore file systems from backup :
# restore –rvqf /dev/rmt0

80
4. Disk management
Procedure 4 : Total rootvg failure
1. Replace bad disk
1. Boot maintenance mode
1. Restore from a mksysb tape
1. import each volume group into the new ODM
(importvg) if needed

81
4. Disk management
Procedure 5 : Total non-rootvg failure
1. Export the volume group from the system :
# exportvg vg_name
2. Check /etc/filesystems.
3. Remove bad disk from ODM and the system :
# rmdev –l hdiskX -d
4. Connect the new disk.
5. If volume group backup is available (savevg) :
# restvg –f /dev/rmt0 hdiskY
6. If no volume group backup is available : Recreate ...
- Volume group (mkvg)
- Logical volumes and file systems (mklv, crfs)
Restore data from a backup :
# restore –rqvf /dev/rmt0

8282
82
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Advanced administration and problem determination

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