Oracle Linux 6 Release Notes

Updated Feb. 2011


This document covers the following topics regarding Oracle Linux 6.

For the latest updates please refer to the online version of release notes available at:

NOTE: An upgrade of Oracle Linux from a beta release is not supported. Further, an in-place upgrade between major versions of Oracle Linux is not supported. Oracle does not recommend an upgrade from earlier major versions of Oracle Linux even though anaconda provides an option to do this upgrade.A fresh installation is strongly recommended rather than a system upgrade between major versions. Customers who want to use new features in Unbreakable Enterprise Kernel can do so without upgrading to Oracle Linux 6 as Oracle Linux 5.6 already includes Unbreakable Enterprise Kernel.

What's new in this release

Oracle Linux 6 includes many new features, including:

Additional new features are provided via Unbreakable Enterprise Kernel.

Changes from the Upstream Release

Packages modified from upstream release

The following packages are modified from the upstream release. All changes are trademark and look/feel related unless otherwise noted below under the specific package.

Packages removed from upstream release

The following packages have been removed.

New Packages added by Oracle

The following packages have been added to the base release


Oracle Linux 6 ships with two sets of kernel packages:

Note:By default, both the Unbreakable Enterprise Kernel and the Red Hat Compatible Kernel are installed on the x86_64 (64 bit) platform, and the system boots the Unbreakable Enterprise Kernel by default. If needed, /etc/grub.conf can be modifed to make the system boot with the Red Hat Compatible Kernel by default.

Unbreakable Enterprise Kernel (x86_64 architecture only)

The Unbreakable Enterprise Kernel is based on the upstream kernel stable source tree with additional performance improvements, including:

The Unbreakable Enterprise Kernel is available for the x86_64 architecture and is the default kernel after installation.

New Features

Known Issues

  1. Incorrect package count (11684244)
  2. Selecting all packages in certain groups during installation might not show the correct count.
  3. kdump does not work with certain controllers and drivers (11680227)
  4. On certain systems, kdump will not work properly. This has been seen on P400i controllers using cciss and hpsa drivers.
  5. hugepages warning messages (9861498)
  6. An application using hugepages may see a warning message like "Using mlock ulimits for SHM_HUGETLB deprecated." To avoid this warning, the application should be configured to use CAP_IPC_LOCK or the process (e.g. Oracle) should be added to the hugetlb_shm_group.
  7. Default reverse path filtering mode affects certain Oracle products (10649976)
  8. Oracle Linux 6 defaults to strict reverse path filtering. Some Oracle products and network storage devices work more reliably when using loose reverse path filtering. To enable loose mode reverse path filtering, issue the following command (assuming you are changing settings for the network interface called eth1). The default setting is 1.
      sysctl net.ipv4.conf.eth1.rp_filter=2 
  9. Receive Packet Steering errors for certain network operations (11071685)
  10. Certain network operations that utilize receive packet steering could cause errors on the system.
  11. Syntax error in sample multipath.conf (10650061)
  12. The sample multipath.conf included in Oracle Linux 6 has an incorrect entry. The path_checker can't be set in the multipath section. Instead, it must be set in the default or device sections.
  13. Spurious udev messages during restore of a failed path (11682171)
  14. When failed paths are restored in a multipath configuration, you may see udevd-work error messages in /var/log/messages. The failed paths do get restored despite these messages.
  15. Default NFS v4 mount options
  16. The default NFS mount option has changed to NFS v4. To mount an NFS volume using NFS v3 (the default in Oracle Linux 5), use the following mount options:
    -o vers=3,mountproto=tcp
  17. Setting serial console in a hardware virtualized (HVM) guest
  18. To set the serial console a hardware virtualized (HVM) guest use following settings in the guest:
  19. Unable to boot a hardware virtualized (HVM) guest that uses paravirtualized drivers (PVHVM)
  20. As a workaround, install the kernel in an HVM guest without paravirtualized drivers.
  21. Unbreakable Linux Network
  22. After an install of Oracle Linux 6, the screens after the first reboot will guide you to register your system to the Unbreakable Linux Network (ULN). If you did not configure your network during the initial installation, the registration process to ULN will not succeed. In this case, you should configure your network by running NetworkManager first (as root). Then restart the ULN registration by running uln_register (as root).
  23. Console appears to hang while booting on certain systems (10094052)
  24. On some hardware, the console may appear to hang during the boot process after starting udev. But the system does boot up properly and is accessible. A workaround to this problem is to add nomodeset as a kernel boot parameter in /etc/grub.conf:
        kernel /vmlinuz-2.6.32-100.28.5.el5.x86_64 ro root=/dev/sd0 nomodeset
  25. Unbreakable Enterprise Kernel doesn't contain vmw_pvscsi driver (11697522)
  26. As a workaround, when creating a new VM in VSphere, do not pick Red Hat Enterprise Linux 6 x86-64 as the OS type but use Oracle Linux 5 x86-64 (or Red Hat Enterprise Linux 5). ESX will then expose the LSI Logic SCSI controller in the VM and the 2.6.32-100.28.* kernel will see the devices properly.
  27. Default IO scheduler
  28. For the Unbreakable Enterprise Kernel, the default IO scheduler is the 'deadline' scheduler.
    For the Red Hat Compatible Kernel, the default IO scheduler is the 'cfq' scheduler.
  29. sched_yield() settings for CFS
  30. For the Unbreakable Enterprise Kernel, kernel.sched_compat_yield=1 by default.
    For the Red Hat Compatible Kernel, kernel.sched_compat_yield=0 by default.
  31. High IO loads on NFS using mmap may fail (11071875)
  32. In some instances, large IO loads on NFS that use mmap may fail and cause the kernel to panic with a message like:
        kernel BUG at mm/truncate.c:469!
  33. Warning message when kdump starts (11688170)
  34. When kdump starts, you may see the following warning message:
        WARNING: No modules scsi_mod found for kernel 2.6.32-100.28.5.el6.x86_64, continuing anyway
    This warning can be ignored. The kdump service does get started and a vmcore does get generated.
  35. Encrypted disk feature not supported (11697886)
  36. Configuring the system with an encrypted disk is currently not supported with the Unbreakable Enterprise Kernel.
Technology Preview Features

The following Technology Preview features are currently not supported under Oracle Linux 6 and may not be functionally complete:

These features are not suitable for production use. However, these features are included to provide the feature with wider exposure.