diff options
| -rw-r--r-- | doc/README.pxe | 3 | ||||
| -rw-r--r-- | doc/develop/distro.rst | 7 |
2 files changed, 9 insertions, 1 deletions
diff --git a/doc/README.pxe b/doc/README.pxe index 9fff2cd5ae9..ba189080e8c 100644 --- a/doc/README.pxe +++ b/doc/README.pxe @@ -178,7 +178,8 @@ devicetree-overlay <path> [...] - if this label is chosen, use tftp to retrieve kaslrseed - set this label to request random number from hwrng as kaslr seed. append <string> - use <string> as the kernel command line when booting this - label. + label. Environment variable references like ${var} are + substituted before boot. initrd <path> - if this label is chosen, use tftp to retrieve the initrd at <path>. it will be stored at the address indicated in diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst index 1d2f9c4c32b..01efce40a29 100644 --- a/doc/develop/distro.rst +++ b/doc/develop/distro.rst @@ -92,6 +92,13 @@ That said, we have some differences to these documents, namely: * If ``-`` is passed as fdt argument and ``CONFIG_SUPPORT_PASSING_ATAGS`` is enabled, then no device tree will be used (legacy booting / pre-dtb kernel). +* The ``append`` string may use environment variables. For example, an + A/B boot setup could use ``append root=PARTLABEL=root_${bootslot}`` + to set the root filesystem to the right one for the selected slot, + assuming the ``bootslot`` environment variable is set before the + extlinux.conf file is processed, and the partition is labeled to + match. + See also doc/README.pxe under 'pxe file format'. One example extlinux.conf generated by the Fedora installer is:: |