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Working with images

The Install-mode setting as set by choosing a PXE menu option on the console of the node before it loads the kernel and ramdisk (figure 5.17). This only affects the current boot. By default the PXE menu install mode option is set to AUTO.

3. The “Next boot install-mode” property of the node configuration.

This can be set using cmgui (figure 5.18): Figure 5.18: cmgui Install-mode Settings For The Node

It can also be set using cmsh with a one-liner like:

cmsh -c "device use node001; set nextinstallmode FULL; commit"

The property is cleared when the node starts up again, after the node-installer finishes its installation tasks. So it is empty unless specifically set by the administrator during the current uptime for the node.

4. The install-mode property can be set in the node configuration using cmgui (figure 5.18), or using cmsh with a one-liner like:

cmsh -c "device use node001; set installmode FULL; commit"

Behavior As Decided By The Install-Mode Value

In section 5.4.4 the node-installer determines the install-mode value, along with when to apply it to a node.

Possible reasons to consider if a node is not even starting to PXE boot in the first place

DHCP may not be running. A check can be done to confirm that DHCP is running on the internal network interface (usually eth0):

[[email protected] ~]# ps u -C dhcpd 
root 2448 0.0 0.0 11208 436 ? Ss Jan22 0:05 /usr/sbin/dhcpd eth0

This may indicate that in cmgui the Allow node booting checkbox in figure3.5 (page 61) needs to be ticked. The equivalent in cmsh is to check if the response to:

cmsh -c "network use internalnet; get nodebooting"

needs to be set to yes.

A rogue DHCP server may be running. If there are all sorts of other machines on the network the nodes are on, then it is possible that there is a rogue DHCP server active on it, perhaps on an IP address that the administrator has forgotten, and interfering with the expected PXE booting. Such stray DHCP servers should be eliminated. In such a case, removing all the connections and switches and just connecting the head node directly to a problem node, NIC-to-NIC, should allow a normal PXE boot to happen. If a normal PXE boot then does happen, it indicates the problem is indeed due to a rogue DHCP server on the more-connected network.

• The boot sequence may be set wrongly in the BIOS. The boot interface should normally be set to be the first boot item in the BIOS.

• There may a bad cable connection. This can be due to moving the

• The TFTP server that sends out the image may have hung. During a normal run, an output similar to this appears when an image is in

the process of being served:

[[email protected] ~]# ps ax | grep [t]ftp

7512 ? Ss 0:03 in.tftpd --maxthread 500 /tftpboot

If the TFTP server is in a zombie state, the head node should be rebooted. If the TFTP service hangs regularly, there is likely a networking hardware issue that requires resolution. Incidentally, grepping the process list for a TFTP service returns nothing when the head node is listening for TFTP requests, but not actively serving a TFTP image. This is because the TFTP service runs under xinet.d and is called on demand. Running

[[email protected] ~]# chkconfig --list

should include in its output the line:

tftp: on

if TFTP is running under xinet.d.

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[Jul 13, 2017] How do I know when a clone operation has completed?

We would like to know when exactly the clone of an image has completed. This is so we can automate some image update and test processes. Ie: we clone an image, apply updates to the clone, assign that updated image to a category, and reboot a node for testing the updated image.

However, the current "clone/commit" process goes into the background. This makes programmatically determining when it finished rather difficult. Can we make the commit of an image clone wait for completion in the cmsh shell so our script will wait before attempting to apply updates?

In 6.0 the --wait option to the commit command makes cmsh wait for any background task to complete. A list of tasks that are waiting for completion can be seen with cmsh -A -c "task list"

For versions of BCM prior to 6.0, the following technique can be used:

The CMDaemon will not start the background copy operation if the target directory already exists. So what you can do from a bash script is something like this:

cp -a /cm/images/default-image /cm/images/new-image
cmsh -c "softwareimage; clone default-image new-image; commit"

The first line guarantees the copy is done (and exits after the cp is done). That means that the second line does pretty much nothing except for housekeeping, which lets cmd then know of new-image. In particular for the second line, cloning, which normally runs in the background to carry out the copy, doesn't do any copying because that was already done.

Applying updates to the images can then be carried out without needing to test if the clone has completed.

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