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.
The install-mode value is typically set to default to AUTO. If AUTO applies
to the current node, it means the node-installer then checks the partitions of the local drive and
its filesystems and recreates them in case of errors. Partitions are checked by comparing the partition
layout of the local drive(s) against the drive layout as configured in the node’s category configuration
and the node configuration. After the node-installer checks the drive(s) and, if required, recreates
the layout, it mounts all filesystems to allow the drive contents to be synchronized with the contents
of the software image.
FULL or MAIN:
If install-mode values of FULL or MAIN apply to the current node
instead, then no partition checking or filesystem checking is done by the node-installer.
NOSYNC:
If the install-mode value of NOSYNC applies, then if the partition and
filesystem checks both show no errors, the node starts up without getting an image synced to it from
the provisioning node. If the partition or the filesystem check show errors, then the node partition
is rewritten, and a known good image is synced across.
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):
[root@bright71 ~]# ps u -C dhcpd
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
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:
[root@bright71 ~]# 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
[root@bright71 ~]# chkconfig --list
should include in its output the line:
tftp: on
if TFTP is running under xinet.d.
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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