Thursday, May 5, 2011

AIX 7 Introduces Renaming Devices


The rendev command enables devices to be renamed. The device to be renamed is specified with the -l flag, and the new desired name is specified with the -n flag.
The new desired name must not exceed 15 characters in length. If the name has already been used or is present in the /dev directory, the operation fails. If the name formed by appending  the new name after the character r is already used as a device name, or appears in the /dev directory, the operation fails.
If the device is in the Available state, the rendev command must unconfigure the device before renaming it. This is similar to the operation performed by the rmdev -l Name command. If the unconfigure operation fails, the renaming will also fail. If the unconfigure succeeds, the rendev command will configure the device, after renaming it, to restore it to the Available state. The -u flag may be used to prevent the device from being configured again after it is renamed.
Some devices may have special requirements on their names in order for other devices or applications to use them. Using the rendev command to rename such a device may result in the device being unusable. Note: To protect the configuration database, the rendev command cannot be interrupted once it has started. Trying to stop this command before completion, could result in a corrupted database.
This functionality was required to help simplify cluster device configuration with the new Cluster Aware AIX (CAA) feature in AIX 7.1.
Here are some examples of using the rendev command on AIX 7.1 (GA) system. In the first example I will rename hdisk3 to hdisk300. Note: hdisk3 is not in use (busy).
If the disk had been allocated to a volume group, I would have needed to varyoff the volume group first.
# lspv
hdisk0          00f61ab2f73e46e2                    rootvg          active
hdisk1          00f61ab20bf28ac6                    None
hdisk2          00f61ab2202f7c0b                    None
hdisk4          00f61ab20b97190d                    None
hdisk3          00f61ab2202f93ab                    None

# rendev -l hdisk3 -n hdisk300 
# lspv
hdisk0          00f61ab2f73e46e2                    rootvg          active
hdisk1          00f61ab20bf28ac6                    None
hdisk2          00f61ab2202f7c0b                    None
hdisk4          00f61ab20b97190d                    None
hdisk300        00f61ab2202f93ab                    None
Easy!
Next, I’ll rename a virtual SCSI adapter. I renamed vscsi0 to vscsi2. Note: I placed the adapter, vscsi0, in a Defined state before renaming the device.
# rmdev -Rl vscsi0
# lsdev -Cc adapter
ent0   Available  Virtual I/O Ethernet Adapter (l-lan)
ent1   Available  Virtual I/O Ethernet Adapter (l-lan)
vsa0   Available  LPAR Virtual Serial Adapter
vscsi0 Defined    Virtual SCSI Client Adapter
vscsi1 Available  Virtual SCSI Client Adapter

# rendev -l vscsi0 -n vscsi2

# lsdev -Cc adapter
ent0   Available  Virtual I/O Ethernet Adapter (l-lan)
ent1   Available  Virtual I/O Ethernet Adapter (l-lan)
vsa0   Available  LPAR Virtual Serial Adapter
vscsi1 Available  Virtual SCSI Client Adapter
vscsi2 Defined    Virtual SCSI Client Adapter
Now I’ll rename a network adapter from ent0 to ent10. I bring down the interface before changing the device name

# lsdev -Cc adapter
ent0   Available  Virtual I/O Ethernet Adapter (l-lan)
ent1   Available  Virtual I/O Ethernet Adapter (l-lan)
vsa0   Available  LPAR Virtual Serial Adapter
vscsi1 Available  Virtual SCSI Client Adapter
vscsi2 Defined    Virtual SCSI Client Adapter

# ifconfig en0
en0: flags=1e080863,480<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),CHAIN>
        inet 10.1.20.19 netmask 0xffff0000 broadcast 10.153.255.255
         tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1

# ifconfig en0 down detach

# rendev -l ent0 -n ent10

# lsdev -Cc adapter
ent1   Available  Virtual I/O Ethernet Adapter (l-lan)
ent10  Available  Virtual I/O Ethernet Adapter (l-lan)
vsa0   Available  LPAR Virtual Serial Adapter
vscsi1 Available  Virtual SCSI Client Adapter
vscsi2 Defined    Virtual SCSI Client Adapter

# rendev -l en0 -n en10

# chdev -l en10 -a state=up
en10 changed


# mkdev -l inet0
inet0 Available



# ifconfig en10
en10: flags=1e080863,480<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),CHAIN>
        inet 10.1.20.19 netmask 0xffff0000 broadcast 10.153.255.255
         tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1

If you want to be creative you can rename devices to anything you like (as long as it’s not more than 15 characters). For example I’ll rename vscsi2 to myvscsiadapter.
# rendev -l vscsi2 -n myvscsiadapter
# lsdev -Cc adapter
ent1           Available  Virtual I/O Ethernet Adapter (l-lan)
myadapter      Available  Virtual I/O Ethernet Adapter (l-lan)
myvscsiadapter Defined    Virtual SCSI Client Adapter
vsa0           Available  LPAR Virtual Serial Adapter
vscsi1         Available  Virtual SCSI Client Adapter
And in the last example I’ll demonstrate changing virtual SCSI adapter device names on a live system. This is single disk system (hdisk0), with two vscsi adapters.
# lspv
hdisk0          00f6048868b4deee                    rootvg          active

# lspath
Enabled hdisk0 vscsi0
Enabled hdisk0 vscsi1

# lsdev -Cc adapter
ent0   Available  Virtual I/O Ethernet Adapter (l-lan)
ent1   Available  Virtual I/O Ethernet Adapter (l-lan)
vsa0   Available  LPAR Virtual Serial Adapter
vscsi0 Available  Virtual SCSI Client Adapter
vscsi1 Available  Virtual SCSI Client Adapter
We ensure the adapter is in a Defined state before renaming it. This will fail otherwise. 
# rmdev -Rl vscsi1
vscsi1 Defined

# lsdev -Cc adapter | grep vscsi
vscsi0 Available  Virtual SCSI Client Adapter
vscsi1 Defined    Virtual SCSI Client Adapter
Now we rename the adapter vscsi1 to vscsi3. 
# rendev -l vscsi1 -n vscsi3

# lsdev -Cc adapter | grep vscsi
vscsi0 Available  Virtual SCSI Client Adapter
vscsi3 Defined    Virtual SCSI Client Adapter
That was easy enough. Now I need to bring the adapter and path online with cfgmgr. The lspath output displays an additional path to vscsi3.

# lspath
Enabled hdisk0 vscsi0
Defined hdisk0 vscsi1

# cfgmgr
Method error (/etc/methods/cfgscsidisk -l hdisk0 ):
        0514-082 The requested function could only be performed for some
                 of the specified paths.

# lspath
Enabled hdisk0 vscsi0
Defined hdisk0 vscsi1
Enabled hdisk0 vscsi3
Now I need to remove the old path to vscsi1. The path to vscsi3 is now Enabled. The adapter, vscsi3, is in an Available state. All is good. 
# rmpath -l hdisk0 -p vscsi1 -d
path Deleted

# lspath
Enabled hdisk0 vscsi0
Enabled hdisk0 vscsi3

# lsdev -Cc adapter | grep vscsi
vscsi0 Available  Virtual SCSI Client Adapter
vscsi3 Available  Virtual SCSI Client Adapter

The same steps need to be repeated for the vscsi0 adapter. This is renamed to vscsi2.

# rmdev -Rl vscsi0
vscsi0 Defined
# lsdev -Cc adapter | grep vscsi
vscsi0 Defined    Virtual SCSI Client Adapter
vscsi3 Available  Virtual SCSI Client Adapter


# rendev -l vscsi0 -n vscsi2

# lsdev -Cc adapter | grep vscsi
vscsi2 Defined    Virtual SCSI Client Adapter
vscsi3 Available  Virtual SCSI Client Adapter


# lspath
Defined hdisk0 vscsi0
Enabled hdisk0 vscsi3

# cfgmgr
Method error (/etc/methods/cfgscsidisk -l hdisk0 ):
        0514-082 The requested function could only be performed for some
                 of the specified paths.

# lspath
Defined hdisk0 vscsi0
Enabled hdisk0 vscsi2
Enabled hdisk0 vscsi3

# rmpath -l hdisk0 -p vscsi0 -d
path Deleted

# cfgmgr
# lspath
Enabled hdisk0 vscsi2
Enabled hdisk0 vscsi3
That’s it. Both adapters have been renamed while the system was in use. No downtime required.

# lsdev -Cc adapter | grep vscsi
vscsi2 Available  Virtual SCSI Client Adapter
vscsi3 Available  Virtual SCSI Client Adapter

# lspath
Enabled hdisk0 vscsi2
Enabled hdisk0 vscsi3

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