freebsd-nq/lib
Paul Dagnelie 108a454a46
Add support for boot environment data to be stored in the label
Modern bootloaders leverage data stored in the root filesystem to 
enable some of their powerful features. GRUB specifically has a grubenv 
file which can store large amounts of configuration data that can be 
read and written at boot time and during normal operation. This allows 
sysadmins to configure useful features like automated failover after 
failed boot attempts. Unfortunately, due to the Copy-on-Write nature 
of ZFS, the standard behavior of these tools cannot handle writing to
ZFS files safely at boot time. We need an alternative way to store 
data that allows the bootloader to make changes to the data.

This work is very similar to work that was done on Illumos to enable 
similar functionality in the FreeBSD bootloader. This patch is different 
in that the data being stored is a raw grubenv file; this file can store 
arbitrary variables and values, and the scripting provided by grub is 
powerful enough that special structures are not required to implement 
advanced behavior.

We repurpose the second padding area in each label to store the grubenv 
file, protected by an embedded checksum. We add two ioctls to get and 
set this data, and libzfs_core and libzfs functions to access them more 
easily. There are no direct command line interfaces to these functions; 
these will be added directly to the bootloader utilities.

Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #10009
2020-05-07 09:36:33 -07:00
..
libavl OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libefi cppcheck: (error) Memory leak: vtoc 2019-12-18 17:25:04 -08:00
libicp ICP: Improve AES-GCM performance 2020-02-10 12:59:50 -08:00
libnvpair Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
libshare Fix static data to link with -fno-common 2020-02-06 09:25:29 -08:00
libspl change libspl list member names to match kernel 2020-04-23 15:53:14 -07:00
libtpool OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libunicode OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
libuutil Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
libzfs Add support for boot environment data to be stored in the label 2020-05-07 09:36:33 -07:00
libzfs_core Add support for boot environment data to be stored in the label 2020-05-07 09:36:33 -07:00
libzpool Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
libzutil Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
Makefile.am Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00