xref: /freebsd/UPDATING (revision 456b5dd815b2a25e7b20ce087a62a59c3e7d06cd)

Updating Information for FreeBSD current users

This file is maintained and copyrighted by M. Warner Losh <imp@freebsd.org>.
See end of file for further details.  For commonly done items, please see the
COMMON ITEMS: section later in the file.  These instructions assume that you
basically know what you are doing.  If not, then please consult the FreeBSD
handbook.

Items affecting the ports and packages system can be found in
/usr/ports/UPDATING.  Please read that file before running portupgrade.

NOTE TO PEOPLE WHO THINK THAT FreeBSD 9.x IS SLOW:
	FreeBSD 9.x has many debugging features turned on, in both the kernel
	and userland.  These features attempt to detect incorrect use of
	system primitives, and encourage loud failure through extra sanity
	checking and fail stop semantics.  They also substantially impact
	system performance.  If you want to do performance measurement,
	benchmarking, and optimization, you'll want to turn them off.  This
	includes various WITNESS- related kernel options, INVARIANTS, malloc
	debugging flags in userland, and various verbose features in the
	kernel.  Many developers choose to disable these features on build
	machines to maximize performance.  (To disable malloc debugging, run
	ln -s aj /etc/malloc.conf.)

20090813:
	Remove the option STOP_NMI.  The default action is now to use NMI only
	for KDB via the newly introduced function stop_cpus_hard() and
	maintain stop_cpus() to just use a normal IPI_STOP on ia32 and amd64.

20090803:
	RELENG_8 branched.

20090719:
	Bump the shared library version numbers for all libraries that do not
	use symbol versioning as part of the 8.0-RELEASE cycle.  Bump
	__FreeBSD_version to 800105.

20090714:
	Due to changes in the implementation of virtual network stack support,
	all network-related kernel modules must be recompiled.  As this change
	breaks the ABI, bump __FreeBSD_version to 800104.

20090713:
	The TOE interface to the TCP syncache has been modified to remove
	struct tcpopt (<netinet/tcp_var.h>) from the ABI of the network stack.
	The cxgb driver is the only TOE consumer affected by this change, and
	needs to be recompiled along with the kernel. As this change breaks
	the ABI, bump __FreeBSD_version to 800103.

20090712:
	Padding has been added to struct tcpcb, sackhint and tcpstat in
	<netinet/tcp_var.h> to facilitate future MFCs and bug fixes whilst
	maintainig the ABI. However, this change breaks the ABI, so bump
	__FreeBSD_version to 800102. User space tools that rely on the size of
	any of these structs (e.g. sockstat) need to be recompiled.

20090630:
	The NFS_LEGACYRPC option has been removed along with the old kernel
	RPC implementation that this option selected. Kernel configurations
	may need to be adjusted.

20090629:
	The network interface device nodes at /dev/net/<interface> have been
	removed.  All ioctl operations can be performed the normal way using
	routing sockets.  The kqueue functionality can generally be replaced
	with routing sockets.

20090628:
	The documentation from the FreeBSD Documentation Project (Handbook,
	FAQ, etc.) is now installed via packages by sysinstall(8) and under
	the /usr/local/share/doc/freebsd directory instead of /usr/share/doc.

20090624:
	The ABI of various structures related to the SYSV IPC API have been
	changed.  As a result, the COMPAT_FREEBSD[456] and COMPAT_43 kernel
	options now all require COMPAT_FREEBSD7.  Bump __FreeBSD_version to
	800100.

20090622:
	Layout of struct vnet has changed as routing related variables were
	moved to their own Vimage module. Modules need to be recompiled.  Bump
	__FreeBSD_version to 800099.

20090619:
	NGROUPS_MAX and NGROUPS have been increased from 16 to 1023 and 1024
	respectively.  As long as no more than 16 groups per process are used,
	no changes should be visible.  When more than 16 groups are used, old
	binaries may fail if they call getgroups() or getgrouplist() with
	statically sized storage.  Recompiling will work around this, but
	applications should be modified to use dynamically allocated storage
	for group arrays as POSIX.1-2008 does not cap an implementation's
	number of supported groups at NGROUPS_MAX+1 as previous versions did.

	NFS and portalfs mounts may also be affected as the list of groups is
	truncated to 16.  Users of NFS who use more than 16 groups, should
	take care that negative group permissions are not used on the exported
	file systems as they will not be reliable unless a GSSAPI based
	authentication method is used.

20090616:
	The compiling option ADAPTIVE_LOCKMGRS has been introduced.  This
	option compiles in the support for adaptive spinning for lockmgrs
	which want to enable it.  The lockinit() function now accepts the flag
	LK_ADAPTIVE in order to make the lock object subject to adaptive
	spinning when both held in write and read mode.

20090613:
	The layout of the structure returned by IEEE80211_IOC_STA_INFO has
	changed.  User applications that use this ioctl need to be rebuilt.

20090611:
	The layout of struct thread has changed.  Kernel and modules need to
	be rebuilt.

20090608:
	The layout of structs ifnet, domain, protosw and vnet_net has changed.
	Kernel modules need to be rebuilt.  Bump __FreeBSD_version to 800097.

20090602:
	window(1) has been removed from the base system. It can now be
	installed from ports. The port is called misc/window.

20090601:
	The way we are storing and accessing `routing table' entries has
	changed. Programs reading the FIB, like netstat, need to be
	re-compiled.

20090601:
	A new netisr implementation has been added for FreeBSD 8.  Network
	file system modules, such as igmp, ipdivert, and others, should be
	rebuilt.
	Bump __FreeBSD_version to 800096.

20090530:
	Remove the tunable/sysctl debug.mpsafevfs as its initial purpose is no
	more valid.

20090530:
	Add VOP_ACCESSX(9).  File system modules need to be rebuilt.
	Bump __FreeBSD_version to 800094.

20090529:
	Add mnt_xflag field to 'struct mount'.  File system modules need to be
	rebuilt.
	Bump __FreeBSD_version to 800093.

20090528:
	The compiling option ADAPTIVE_SX has been retired while it has been
	introduced the option NO_ADAPTIVE_SX which handles the reversed logic.
	The KPI for sx_init_flags() changes as accepting flags:
	SX_ADAPTIVESPIN flag has been retired while the SX_NOADAPTIVE flag has
	been introduced in order to handle the reversed logic.
	Bump __FreeBSD_version to 800092.

20090527:
	Add support for hierarchical jails.  Remove global securelevel.
	Bump __FreeBSD_version to 800091.

20090523:
	The layout of struct vnet_net has changed, therefore modules
	need to be rebuilt.
	Bump __FreeBSD_version to 800090.

20090523:
	The newly imported zic(8) produces a new format in the output. Please
	run tzsetup(8) to install the newly created data to /etc/localtime.

20090520:
	The sysctl tree for the usb stack has renamed from hw.usb2.* to
	hw.usb.* and is now consistent again with previous releases.

20090520:
	802.11 monitor mode support was revised and driver api's were changed.
	Drivers dependent on net80211 now support DLT_IEEE802_11_RADIO instead
	of DLT_IEEE802_11.  No user-visible data structures were changed but
	applications that use DLT_IEEE802_11 may require changes.
	Bump __FreeBSD_version to 800088.

20090430:
	The layout of the following structs has changed: sysctl_oid,
	socket, ifnet, inpcbinfo, tcpcb, syncache_head, vnet_inet,
	vnet_inet6 and vnet_ipfw.  Most modules need to be rebuild or
	panics may be experienced.  World rebuild is required for
	correctly checking networking state from userland.
	Bump __FreeBSD_version to 800085.

20090429:
	MLDv2 and Source-Specific Multicast (SSM) have been merged
	to the IPv6 stack. VIMAGE hooks are in but not yet used.
	The implementation of SSM within FreeBSD's IPv6 stack closely
	follows the IPv4 implementation.

	For kernel developers:

	* The most important changes are that the ip6_output() and
	  ip6_input() paths no longer take the IN6_MULTI_LOCK,
	  and this lock has been downgraded to a non-recursive mutex.

	* As with the changes to the IPv4 stack to support SSM, filtering
	  of inbound multicast traffic must now be performed by transport
	  protocols within the IPv6 stack. This does not apply to TCP and
	  SCTP, however, it does apply to UDP in IPv6 and raw IPv6.

	* The KPIs used by IPv6 multicast are similar to those used by
	  the IPv4 stack, with the following differences:
	   * im6o_mc_filter() is analogous to imo_multicast_filter().
	   * The legacy KAME entry points in6_joingroup and in6_leavegroup()
	     are shimmed to in6_mc_join() and in6_mc_leave() respectively.
	   * IN6_LOOKUP_MULTI() has been deprecated and removed.
	   * IPv6 relies on MLD for the DAD mechanism. KAME's internal KPIs
	     for MLDv1 have an additional 'timer' argument which is used to
	     jitter the initial membership report for the solicited-node
	     multicast membership on-link.
	   * This is not strictly needed for MLDv2, which already jitters
	     its report transmissions.  However, the 'timer' argument is
	     preserved in case MLDv1 is active on the interface.

	* The KAME linked-list based IPv6 membership implementation has
	  been refactored to use a vector similar to that used by the IPv4
	  stack.
	  Code which maintains a list of its own multicast memberships
	  internally, e.g. carp, has been updated to reflect the new
	  semantics.

	* There is a known Lock Order Reversal (LOR) due to in6_setscope()
	  acquiring the IF_AFDATA_LOCK and being called within ip6_output().
	  Whilst MLDv2 tries to avoid this otherwise benign LOR, it is an
	  implementation constraint which needs to be addressed in HEAD.

	For application developers:

	* The changes are broadly similar to those made for the IPv4
	  stack.

	* The use of IPv4 and IPv6 multicast socket options on the same
	  socket, using mapped addresses, HAS NOT been tested or supported.

	* There are a number of issues with the implementation of various
	  IPv6 multicast APIs which need to be resolved in the API surface
	  before the implementation is fully compatible with KAME userland
	  use, and these are mostly to do with interface index treatment.

	* The literature available discusses the use of either the delta / ASM
	  API with setsockopt(2)/getsockopt(2), or the full-state / ASM API
	  using setsourcefilter(3)/getsourcefilter(3). For more information
	  please refer to RFC 3768, 'Socket Interface Extensions for
	  Multicast Source Filters'.

	* Applications which use the published RFC 3678 APIs should be fine.

	For systems administrators:

	* The mtest(8) utility has been refactored to support IPv6, in
	  addition to IPv4. Interface addresses are no longer accepted
	  as arguments, their names must be used instead. The utility
	  will map the interface name to its first IPv4 address as
	  returned by getifaddrs(3).

	* The ifmcstat(8) utility has also been updated to print the MLDv2
	  endpoint state and source filter lists via sysctl(3).

	* The net.inet6.ip6.mcast.loop sysctl may be tuned to 0 to disable
	  loopback of IPv6 multicast datagrams by default; it defaults to 1
	  to preserve the existing behaviour. Disabling multicast loopback is
	  recommended for optimal system performance.

	* The IPv6 MROUTING code has been changed to examine this sysctl
	  instead of attempting to perform a group lookup before looping
	  back forwarded datagrams.

	Bump __FreeBSD_version to 800084.

20090422:
	Implement low-level Bluetooth HCI API.
	Bump __FreeBSD_version to 800083.

20090419:
	The layout of struct malloc_type, used by modules to register new
	memory allocation types, has changed.  Most modules will need to
	be rebuilt or panics may be experienced.
	Bump __FreeBSD_version to 800081.

20090415:
	Anticipate overflowing inp_flags - add inp_flags2.
	This changes most offsets in inpcb, so checking v4 connection
	state will require a world rebuild.
	Bump __FreeBSD_version to 800080.

20090415:
	Add an llentry to struct route and struct route_in6. Modules
	embedding a struct route will need to be recompiled.
	Bump __FreeBSD_version to 800079.

20090414:
	The size of rt_metrics_lite and by extension rtentry has changed.
	Networking administration apps will need to be recompiled.
	The route command now supports show as an alias for get, weighting
	of routes, sticky and nostick flags to alter the behavior of stateful
	load balancing.
	Bump __FreeBSD_version to 800078.

20090408:
	Do not use Giant for kbdmux(4) locking. This is wrong and
	apparently causing more problems than it solves. This will
	re-open the issue where interrupt handlers may race with
	kbdmux(4) in polling mode. Typical symptoms include (but
	not limited to) duplicated and/or missing characters when
	low level console functions (such as gets) are used while
	interrupts are enabled (for example geli password prompt,
	mountroot prompt etc.). Disabling kbdmux(4) may help.

20090407:
	The size of structs vnet_net, vnet_inet and vnet_ipfw has changed;
	kernel modules referencing any of the above need to be recompiled.
	Bump __FreeBSD_version to 800075.

20090320:
	GEOM_PART has become the default partition slicer for storage devices,
	replacing GEOM_MBR, GEOM_BSD, GEOM_PC98 and GEOM_GPT slicers. It
	introduces some changes:

	MSDOS/EBR: the devices created from MSDOS extended partition entries
	(EBR) can be named differently than with GEOM_MBR and are now symlinks
	to devices with offset-based names. fstabs may need to be modified.

	BSD: the "geometry does not match label" warning is harmless in most
	cases but it points to problems in file system misalignment with
	disk geometry. The "c" partition is now implicit, covers the whole
	top-level drive and cannot be (mis)used by users.

	General: Kernel dumps are now not allowed to be written to devices
	whose partition types indicate they are meant to be used for file
	systems (or, in case of MSDOS partitions, as something else than
	the "386BSD" type).

	Most of these changes date approximately from 200812.

20090319:
	The uscanner(4) driver has been removed from the kernel. This follows
	Linux removing theirs in 2.6 and making libusb the default interface
	(supported by sane).

20090319:
	The multicast forwarding code has been cleaned up. netstat(1)
	only relies on KVM now for printing bandwidth upcall meters.
	The IPv4 and IPv6 modules are split into ip_mroute_mod and
	ip6_mroute_mod respectively. The config(5) options for statically
	compiling this code remain the same, i.e. 'options MROUTING'.

20090315:
	Support for the IFF_NEEDSGIANT network interface flag has been
	removed, which means that non-MPSAFE network device drivers are no
	longer supported.  In particular, if_ar, if_sr, and network device
	drivers from the old (legacy) USB stack can no longer be built or
	used.

20090313:
	POSIX.1 Native Language Support (NLS) has been enabled in libc and
	a bunch of new language catalog files have also been added.
	This means that some common libc messages are now localized and
	they depend on the LC_MESSAGES environmental variable.

20090313:
	The k8temp(4) driver has been renamed to amdtemp(4) since
	support for K10 and K11 CPU families was added.

20090309:
	IGMPv3 and Source-Specific Multicast (SSM) have been merged
	to the IPv4 stack. VIMAGE hooks are in but not yet used.

	For kernel developers, the most important changes are that the
	ip_output() and ip_input() paths no longer take the IN_MULTI_LOCK(),
	and this lock has been downgraded to a non-recursive mutex.

	Transport protocols (UDP, Raw IP) are now responsible for filtering
	inbound multicast traffic according to group membership and source
	filters. The imo_multicast_filter() KPI exists for this purpose.
	Transports which do not use multicast (SCTP, TCP) already reject
	multicast by default. Forwarding and receive performance may improve
	as a mutex acquisition is no longer needed in the ip_input()
	low-level input path.  in_addmulti() and in_delmulti() are shimmed
	to new KPIs which exist to support SSM in-kernel.

	For application developers, it is recommended that loopback of
	multicast datagrams be disabled for best performance, as this
	will still cause the lock to be taken for each looped-back
	datagram transmission. The net.inet.ip.mcast.loop sysctl may
	be tuned to 0 to disable loopback by default; it defaults to 1
	to preserve the existing behaviour.

	For systems administrators, to obtain best performance with
	multicast reception and multiple groups, it is always recommended
	that a card with a suitably precise hash filter is used. Hash
	collisions will still result in the lock being taken within the
	transport protocol input path to check group membership.

	If deploying FreeBSD in an environment with IGMP snooping switches,
	it is recommended that the net.inet.igmp.sendlocal sysctl remain
	enabled; this forces 224.0.0.0/24 group membership to be announced
	via IGMP.

	The size of 'struct igmpstat' has changed; netstat needs to be
	recompiled to reflect this.
	Bump __FreeBSD_version to 800070.

20090309:
	libusb20.so.1 is now installed as libusb.so.1 and the ports system
	updated to use it. This requires a buildworld/installworld in order to
	update the library and dependencies (usbconfig, etc). Its advisable to
	rebuild all ports which uses libusb. More specific directions are given
	in the ports collection UPDATING file. Any /etc/libmap.conf entries for
	libusb are no longer required and can be removed.

20090302:
	A workaround is committed to allow the creation of System V shared
	memory segment of size > 2 GB on the 64-bit architectures.
	Due to a limitation of the existing ABI, the shm_segsz member
	of the struct shmid_ds, returned by shmctl(IPC_STAT) call is
	wrong for large segments. Note that limits must be explicitly
	raised to allow such segments to be created.

20090301:
	The layout of struct ifnet has changed, requiring a rebuild of all
	network device driver modules.

20090227:
	The /dev handling for the new USB stack has changed, a
	buildworld/installworld is required for libusb20.

20090223:
	The new USB2 stack has now been permanently moved in and all kernel and
	module names reverted to their previous values (eg, usb, ehci, ohci,
	ums, ...).  The old usb stack can be compiled in by prefixing the name
	with the letter 'o', the old usb modules have been removed.
	Updating entry 20090216 for xorg and 20090215 for libmap may still
	apply.

20090217:
	The rc.conf(5) option if_up_delay has been renamed to
	defaultroute_delay to better reflect its purpose. If you have
	customized this setting in /etc/rc.conf you need to update it to
	use the new name.

20090216:
	xorg 7.4 wants to configure its input devices via hald which does not
	yet work with USB2. If the keyboard/mouse does not work in xorg then
	add
		Option "AllowEmptyInput" "off"
	to your ServerLayout section.  This will cause X to use the configured
	kbd and mouse sections from your xorg.conf.

20090215:
	The GENERIC kernels for all architectures now default to the new USB2
	stack. No kernel config options or code have been removed so if a
	problem arises please report it and optionally revert to the old USB
	stack. If you are loading USB kernel modules or have a custom kernel
	that includes GENERIC then ensure that usb names are also changed over,
	eg uftdi -> usb2_serial_ftdi.

	Older programs linked against the ports libusb 0.1 need to be
	redirected to the new stack's libusb20.  /etc/libmap.conf can
	be used for this:
		# Map old usb library to new one for usb2 stack
		libusb-0.1.so.8	libusb20.so.1

20090203:
	The ichsmb(4) driver has been changed to require SMBus slave
	addresses be left-justified (xxxxxxx0b) rather than right-justified.
	All of the other SMBus controller drivers require left-justified
	slave addresses, so this change makes all the drivers provide the
	same interface.

20090201:
	INET6 statistics (struct ip6stat) was updated.
	netstat(1) needs to be recompiled.

20090119:
	NTFS has been removed from GENERIC kernel on amd64 to match
	GENERIC on i386. Should not cause any issues since mount_ntfs(8)
	will load ntfs.ko module automatically when NTFS support is
	actually needed, unless ntfs.ko is not installed or security
	level prohibits loading kernel modules. If either is the case,
	"options NTFS" has to be added into kernel config.

20090115:
	TCP Appropriate Byte Counting (RFC 3465) support added to kernel.
	New field in struct tcpcb breaks ABI, so bump __FreeBSD_version to
	800061. User space tools that rely on the size of struct tcpcb in
	tcp_var.h (e.g. sockstat) need to be recompiled.

20081225:
	ng_tty(4) module updated to match the new TTY subsystem.
	Due to API change, user-level applications must be updated.
	New API support added to mpd5 CVS and expected to be present
	in next mpd5.3 release.

20081219:
	With __FreeBSD_version 800060 the makefs tool is part of
	the base system (it was a port).

20081216:
	The afdata and ifnet locks have been changed from mutexes to
	rwlocks, network modules will need to be re-compiled.

20081214:
	__FreeBSD_version 800059 incorporates the new arp-v2 rewrite.
	RTF_CLONING, RTF_LLINFO and RTF_WASCLONED flags are eliminated.
	The new code reduced struct rtentry{} by 16 bytes on 32-bit
	architecture and 40 bytes on 64-bit architecture. The userland
	applications "arp" and "ndp" have been updated accordingly.
	The output from "netstat -r" shows only routing entries and
	none of the L2 information.

20081130:
	__FreeBSD_version 800057 marks the switchover from the
	binary ath hal to source code. Users must add the line:

	options	AH_SUPPORT_AR5416

	to their kernel config files when specifying:

	device	ath_hal

	The ath_hal module no longer exists; the code is now compiled
	together with the driver in the ath module.  It is now
	possible to tailor chip support (i.e. reduce the set of chips
	and thereby the code size); consult ath_hal(4) for details.

20081121:
	__FreeBSD_version 800054 adds memory barriers to
	<machine/atomic.h>, new interfaces to ifnet to facilitate
	multiple hardware transmit queues for cards that support
	them, and a lock-less ring-buffer implementation to
	enable drivers to more efficiently manage queueing of
	packets.

20081117:
	A new version of ZFS (version 13) has been merged to -HEAD.
	This version has zpool attribute "listsnapshots" off by
	default, which means "zfs list" does not show snapshots,
	and is the same as Solaris behavior.

20081028:
	dummynet(4) ABI has changed. ipfw(8) needs to be recompiled.

20081009:
	The uhci, ohci, ehci and slhci USB Host controller drivers have
	been put into separate modules. If you load the usb module
	separately through loader.conf you will need to load the
	appropriate *hci module as well. E.g. for a UHCI-based USB 2.0
	controller add the following to loader.conf:

		uhci_load="YES"
		ehci_load="YES"

20081009:
	The ABI used by the PMC toolset has changed.  Please keep
	userland (libpmc(3)) and the kernel module (hwpmc(4)) in
	sync.

20080820:
	The TTY subsystem of the kernel has been replaced by a new
	implementation, which provides better scalability and an
	improved driver model. Most common drivers have been migrated to
	the new TTY subsystem, while others have not. The following
	drivers have not yet been ported to the new TTY layer:

	PCI/ISA:
		cy, digi, rc, rp, sio

	USB:
		ubser, ucycom

	Line disciplines:
		ng_h4, ng_tty, ppp, sl, snp

	Adding these drivers to your kernel configuration file shall
	cause compilation to fail.

20080818:
	ntpd has been upgraded to 4.2.4p5.

20080801:
	OpenSSH has been upgraded to 5.1p1.

	For many years, FreeBSD's version of OpenSSH preferred DSA
	over RSA for host and user authentication keys.  With this
	upgrade, we've switched to the vendor's default of RSA over
	DSA.  This may cause upgraded clients to warn about unknown
	host keys even for previously known hosts.  Users should
	follow the usual procedure for verifying host keys before
	accepting the RSA key.

	This can be circumvented by setting the "HostKeyAlgorithms"
	option to "ssh-dss,ssh-rsa" in ~/.ssh/config or on the ssh
	command line.

	Please note that the sequence of keys offered for
	authentication has been changed as well.  You may want to
	specify IdentityFile in a different order to revert this
	behavior.

20080713:
	The sio(4) driver has been removed from the i386 and amd64
	kernel configuration files. This means uart(4) is now the
	default serial port driver on those platforms as well.

	To prevent collisions with the sio(4) driver, the uart(4) driver
	uses different names for its device nodes. This means the
	onboard serial port will now most likely be called "ttyu0"
	instead of "ttyd0". You may need to reconfigure applications to
	use the new device names.

	When using the serial port as a boot console, be sure to update
	/boot/device.hints and /etc/ttys before booting the new kernel.
	If you forget to do so, you can still manually specify the hints
	at the loader prompt:

		set hint.uart.0.at="isa"
		set hint.uart.0.port="0x3F8"
		set hint.uart.0.flags="0x10"
		set hint.uart.0.irq="4"
		boot -s

20080609:
	The gpt(8) utility has been removed. Use gpart(8) to partition
	disks instead.

20080603:
	The version that Linuxulator emulates was changed from 2.4.2
	to 2.6.16. If you experience any problems with Linux binaries
	please try to set sysctl compat.linux.osrelease to 2.4.2 and
	if it fixes the problem contact emulation mailing list.

20080525:
	ISDN4BSD (I4B) was removed from the src tree. You may need to
	update a your kernel configuration and remove relevant entries.

20080509:
	I have checked in code to support multiple routing tables.
	See the man pages setfib(1) and setfib(2).
	This is a hopefully backwards compatible version,
	but to make use of it you need to compile your kernel
	with options ROUTETABLES=2 (or more up to 16).

20080420:
	The 802.11 wireless support was redone to enable multi-bss
	operation on devices that are capable.  The underlying device
	is no longer used directly but instead wlanX devices are
	cloned with ifconfig.  This requires changes to rc.conf files.
	For example, change:
		ifconfig_ath0="WPA DHCP"
	to
		wlans_ath0=wlan0
		ifconfig_wlan0="WPA DHCP"
	see rc.conf(5) for more details.  In addition, mergemaster of
	/etc/rc.d is highly recommended.  Simultaneous update of userland
	and kernel wouldn't hurt either.

	As part of the multi-bss changes the wlan_scan_ap and wlan_scan_sta
	modules were merged into the base wlan module.  All references
	to these modules (e.g. in kernel config files) must be removed.

20080408:
	psm(4) has gained write(2) support in native operation level.
	Arbitrary commands can be written to /dev/psm%d and status can
	be read back from it.  Therefore, an application is responsible
	for status validation and error recovery.  It is a no-op in
	other operation levels.

20080312:
	Support for KSE threading has been removed from the kernel.  To
	run legacy applications linked against KSE libmap.conf may
	be used.  The following libmap.conf may be used to ensure
	compatibility with any prior release:

	libpthread.so.1 libthr.so.1
	libpthread.so.2 libthr.so.2
	libkse.so.3 libthr.so.3

20080301:
	The layout of struct vmspace has changed. This affects libkvm
	and any executables that link against libkvm and use the
	kvm_getprocs() function. In particular, but not exclusively,
	it affects ps(1), fstat(1), pkill(1), systat(1), top(1) and w(1).
	The effects are minimal, but it's advisable to upgrade world
	nonetheless.

20080229:
	The latest em driver no longer has support in it for the
	82575 adapter, this is now moved to the igb driver. The
	split was done to make new features that are incompatible
	with older hardware easier to do.

20080220:
	The new geom_lvm(4) geom class has been renamed to geom_linux_lvm(4),
	likewise the kernel option is now GEOM_LINUX_LVM.

20080211:
	The default NFS mount mode has changed from UDP to TCP for
	increased reliability.  If you rely on (insecurely) NFS
	mounting across a firewall you may need to update your
	firewall rules.

20080208:
	Belatedly note the addition of m_collapse for compacting
	mbuf chains.

20080126:
	The fts(3) structures have been changed to use adequate
	integer types for their members and so to be able to cope
	with huge file trees.  The old fts(3) ABI is preserved
	through symbol versioning in libc, so third-party binaries
	using fts(3) should still work, although they will not take
	advantage of the extended types.  At the same time, some
	third-party software might fail to build after this change
	due to unportable assumptions made in its source code about
	fts(3) structure members.  Such software should be fixed
	by its vendor or, in the worst case, in the ports tree.
	FreeBSD_version 800015 marks this change for the unlikely
	case that a portable fix is impossible.

20080123:
	To upgrade to -current after this date, you must be running
	FreeBSD not older than 6.0-RELEASE.  Upgrading to -current
	from 5.x now requires a stop over at RELENG_6 or RELENG_7 systems.

20071128:
	The ADAPTIVE_GIANT kernel option has been retired because its
	functionality is the default now.

20071118:
	The AT keyboard emulation of sunkbd(4) has been turned on
	by default. In order to make the special symbols of the Sun
	keyboards driven by sunkbd(4) work under X these now have
	to be configured the same way as Sun USB keyboards driven
	by ukbd(4) (which also does AT keyboard emulation), f.e.:

	Option	"XkbLayout" "us"
	Option	"XkbRules" "xorg"
	Option	"XkbSymbols" "pc(pc105)+sun_vndr/usb(sun_usb)+us"

20071024:
	It has been decided that it is desirable to provide ABI
	backwards compatibility to the FreeBSD 4/5/6 versions of the
	PCIOCGETCONF, PCIOCREAD and PCIOCWRITE IOCTLs, which was
	broken with the introduction of PCI domain support (see the
	20070930 entry). Unfortunately, this required the ABI of
	PCIOCGETCONF to be broken again in order to be able to
	provide backwards compatibility to the old version of that
	IOCTL. Thus consumers of PCIOCGETCONF have to be recompiled
	again. As for prominent ports this affects neither pciutils
	nor xorg-server this time, the hal port needs to be rebuilt
	however.

20071020:
	The misnamed kthread_create() and friends have been renamed
	to kproc_create() etc. Many of the callers already
	used kproc_start()..
	I will return kthread_create() and friends in a while
	with implementations that actually create threads, not procs.
	Renaming corresponds with version 800002.

20071010:
	RELENG_7 branched.

COMMON ITEMS:

	General Notes
	-------------
	Avoid using make -j when upgrading.  While generally safe, there are
	sometimes problems using -j to upgrade.  If your upgrade fails with
	-j, please try again wtihout -j.  From time to time in the past there
	have been problems using -j with buildworld and/or installworld.  This
	is especially true when upgrading between "distant" versions (eg one
	that cross a major release boundary or several minor releases, or when
	several months have passed on the -current branch).

	Sometimes, obscure build problems are the result of environment
	poisoning.  This can happen because the make utility reads its
	environment when searching for values for global variables.  To run
	your build attempts in an "environmental clean room", prefix all make
	commands with 'env -i '.  See the env(1) manual page for more details.

	When upgrading from one major version to another it is generally best
	to upgrade to the latest code in the currently installed branch first,
	then do an upgrade to the new branch. This is the best-tested upgrade
	path, and has the highest probability of being successful.  Please try
	this approach before reporting problems with a major version upgrade.

	To build a kernel
	-----------------
	If you are updating from a prior version of FreeBSD (even one just
	a few days old), you should follow this procedure.  It is the most
	failsafe as it uses a /usr/obj tree with a fresh mini-buildworld,

	make kernel-toolchain
	make -DALWAYS_CHECK_MAKE buildkernel KERNCONF=YOUR_KERNEL_HERE
	make -DALWAYS_CHECK_MAKE installkernel KERNCONF=YOUR_KERNEL_HERE

	To test a kernel once
	---------------------
	If you just want to boot a kernel once (because you are not sure
	if it works, or if you want to boot a known bad kernel to provide
	debugging information) run
	make installkernel KERNCONF=YOUR_KERNEL_HERE KODIR=/boot/testkernel
	nextboot -k testkernel

	To just build a kernel when you know that it won't mess you up
	--------------------------------------------------------------
	This assumes you are already running a CURRENT system.  Replace
	${arch} with the architecture of your machine (e.g. "i386",
	"arm", "amd64", "ia64", "pc98", "sparc64", "powerpc", "mips", etc).

	cd src/sys/${arch}/conf
	config KERNEL_NAME_HERE
	cd ../compile/KERNEL_NAME_HERE
	make depend
	make
	make install

	If this fails, go to the "To build a kernel" section.

	To rebuild everything and install it on the current system.
	-----------------------------------------------------------
	# Note: sometimes if you are running current you gotta do more than
	# is listed here if you are upgrading from a really old current.

	<make sure you have good level 0 dumps>
	make buildworld
	make kernel KERNCONF=YOUR_KERNEL_HERE
							[1]
	<reboot in single user>				[3]
	mergemaster -p					[5]
	make installworld
	make delete-old
	mergemaster					[4]
	<reboot>


	To cross-install current onto a separate partition
	--------------------------------------------------
	# In this approach we use a separate partition to hold
	# current's root, 'usr', and 'var' directories.   A partition
	# holding "/", "/usr" and "/var" should be about 2GB in
	# size.

	<make sure you have good level 0 dumps>
	<boot into -stable>
	make buildworld
	make buildkernel KERNCONF=YOUR_KERNEL_HERE
	<maybe newfs current's root partition>
	<mount current's root partition on directory ${CURRENT_ROOT}>
	make installworld DESTDIR=${CURRENT_ROOT}
	make distribution DESTDIR=${CURRENT_ROOT} # if newfs'd
	make installkernel KERNCONF=YOUR_KERNEL_HERE DESTDIR=${CURRENT_ROOT}
	cp /etc/fstab ${CURRENT_ROOT}/etc/fstab 		   # if newfs'd
	<edit ${CURRENT_ROOT}/etc/fstab to mount "/" from the correct partition>
	<reboot into current>
	<do a "native" rebuild/install as described in the previous section>
	<maybe install compatibility libraries from ports/misc/compat*>
	<reboot>


	To upgrade in-place from 8.x-stable to current
	----------------------------------------------
	<make sure you have good level 0 dumps>
	make buildworld					[9]
	make kernel KERNCONF=YOUR_KERNEL_HERE		[8]
							[1]
	<reboot in single user>				[3]
	mergemaster -p					[5]
	make installworld
	make delete-old
	mergemaster -i					[4]
	<reboot>

	Make sure that you've read the UPDATING file to understand the
	tweaks to various things you need.  At this point in the life
	cycle of current, things change often and you are on your own
	to cope.  The defaults can also change, so please read ALL of
	the UPDATING entries.

	Also, if you are tracking -current, you must be subscribed to
	freebsd-current@freebsd.org.  Make sure that before you update
	your sources that you have read and understood all the recent
	messages there.  If in doubt, please track -stable which has
	much fewer pitfalls.

	[1] If you have third party modules, such as vmware, you
	should disable them at this point so they don't crash your
	system on reboot.

	[3] From the bootblocks, boot -s, and then do
		fsck -p
		mount -u /
		mount -a
		cd src
		adjkerntz -i		# if CMOS is wall time
	Also, when doing a major release upgrade, it is required that
	you boot into single user mode to do the installworld.

	[4] Note: This step is non-optional.  Failure to do this step
	can result in a significant reduction in the functionality of the
	system.  Attempting to do it by hand is not recommended and those
	that pursue this avenue should read this file carefully, as well
	as the archives of freebsd-current and freebsd-hackers mailing lists
	for potential gotchas.

	[5] Usually this step is a noop.  However, from time to time
	you may need to do this if you get unknown user in the following
	step.  It never hurts to do it all the time.  You may need to
	install a new mergemaster (cd src/usr.sbin/mergemaster && make
	install) after the buildworld before this step if you last updated
	from current before 20020224 or from -stable before 20020408.

	[8] In order to have a kernel that can run the 4.x binaries needed to
	do an installworld, you must include the COMPAT_FREEBSD4 option in
	your kernel.  Failure to do so may leave you with a system that is
	hard to boot to recover. A similar kernel option COMPAT_FREEBSD5 is
	required to run the 5.x binaries on more recent kernels.  And so on
	for COMPAT_FREEBSD6 and COMPAT_FREEBSD7.

	Make sure that you merge any new devices from GENERIC since the
	last time you updated your kernel config file.

	[9] When checking out sources, you must include the -P flag to have
	cvs prune empty directories.

	If CPUTYPE is defined in your /etc/make.conf, make sure to use the
	"?=" instead of the "=" assignment operator, so that buildworld can
	override the CPUTYPE if it needs to.

	MAKEOBJDIRPREFIX must be defined in an environment variable, and
	not on the command line, or in /etc/make.conf.  buildworld will
	warn if it is improperly defined.
FORMAT:

This file contains a list, in reverse chronological order, of major
breakages in tracking -current.  Not all things will be listed here,
and it only starts on October 16, 2004.  Updating files can found in
previous releases if your system is older than this.

Copyright information:

Copyright 1998-2009 M. Warner Losh.  All Rights Reserved.

Redistribution, publication, translation and use, with or without
modification, in full or in part, in any form or format of this
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED.  IN NO EVENT SHALL WARNER LOSH BE LIABLE FOR ANY DIRECT,
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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