tmpfs file system causes SLES11 network to not come up when booting

This document (7006027) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 11 (FCS)

Situation

The network interface(s) will not come up during boot up. They will come up using the ifup command immediately after the system finishes the boot process, but not during it.

The problem can occur on:

Xen para-virtualized
VMware (Workstation, Server, ESX)
Physical servers

It is not based on special hardware (network cards).

The boot.msg file shows that the setup of eth0 times out:

Setting up (localfs) network interfaces:

    lo
    lo        IP address: 127.0.0.1/8
              IP address: 127.0.0.2/8
doneWaiting for mandatory devices:  eth0 __NSC__
29 28 27 26 24 23 22 21 20 19 17 16 15 14 13 12 10 9 8 7 6 5 4 2 1 0
    eth0      device: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet
(rev 02)
    eth0      is down
failed    eth0      interface could not be set up until now
failedSetting up service (localfs) network  .  .  .  .  .  .  .  .  .  .failed

Resolution

The best resolution is to move to SLES11 SP1 or later.
A change was made beginning with SLES11 SP1 whereas the cause of this issue was removed.

Cause

The problem is that /dev/shm is holding state information for the network devices when a new mount, for type tmpfs, is enacted. The new, virtual mount does not contain the state information so the network device will activate without intervention.

Additional Information

Until the host can be updated to SLES11SP1 (or later), a workaround is to:

remove the following line from /etc/fstab

shmfs /dev/shm tmpfs size=240m
add the following line to /etc/fstab

udev /dev tmpfs noauto,size=240m 0 0

Notes:

The 240m size is just included as an example. The default size for tmpfs is 50% of RAM and can be modified (although leaving the default is suggested if no specific application requirements are identified).
The udev mnt is visible in the output of "cat /proc/mounts" and is mounted by the /etc/init.d/boot "System Boot Control" script (boot log mesgs are "Mounting tmpfs at /dev" and/or "Remounting tmpfs at /dev" [applying the size parameter]) already before any /etc/init.d/boot.* scripts are called.

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