Provided by: iucode-tool_1.0.1-1_amd64 
NAME
iucode_tool - Tool to manipulate Intel® IA32/X86_64 microcode bundles
SYNOPSIS
iucode_tool [options] [[-ttype] filename|dirname] ...
DESCRIPTION
iucode_tool is an utility that can load Intel® processor microcode data from files in both text and
binary microcode bundle formats.
It can output a list of the microcodes in these files, merge them, upload them to the kernel (to upgrade
the microcode in the system processor cores) or write some of them out to a file in binary format for
later use.
iucode_tool will load all microcodes in the specified files and directories to memory, in order to
process them. Duplicated and outdated microcodes will be discarded. It can read microcode data from
standard input (stdin), by specifying a file name of "-" (minus sign).
Microcode data files are assumed to be in .dat text format if they have a .dat suffix, and to be in
binary format otherwise. Standard input (stdin) is assumed to be in .dat text format. The -t option can
be used to change the type of the files specified after it, including for stdin.
If a directory is specified, all files whose names do not begin with a dot will be loaded, in unspecified
order. Nested directories are skipped.
Empty files and directories are ignored, and will be skipped.
You can select which microcodes should be written out, listed or uploaded to the kernel using the -S, -s,
--date-before and --date-after options. Should none of those options be specified, all microcodes will
be selected.
You can upload the selected microcodes to the kernel, write them out to a file (in binary format), to a
Linux early initramfs archive, to per-processor-signature files in a directory, or to per-microcode files
in a directory using the -w, --write-earlyfw, -k, -K, and -W options.
For more information about Intel processor microcodes, please read the included documentation and the
Intel manuals listed in the SEE ALSO section.
OPTIONS
iucode_tool accepts the following options:
-q, --quiet
Inhibit usual output.
-v, --verbose
Print more information. Use more than once for added verbosity.
-h, -?, --help
List all available options and their meanings.
--usage
Show summary of options.
-V, --version
Show version of program.
-t type
Sets the file type of the following files. type can be:
b binary format. This is the same format used by the kernel driver and the BIOS/EFI, which
is described in detail by the Intel 64 and IA-32 Architectures Software Developer's Manual,
Volume 3A, section 9.11.
d Intel microcode .dat text format. This is the format normally used by Intel to distribute
microcode data files.
a (default) iucode_tool will use the filename suffix to select the file type: .dat text
format for files that have a .dat suffix, and binary type otherwise. Note that for stdin,
.dat text format is assumed.
--downgrade
When multiple versions of the microcode for a specific processor are available from different
files, keep the one from the file loaded last, regardless of revision levels. Files are always
loaded in the order they were specified in the command line. This option has no effect when just
one file has been loaded.
--no-downgrade
When multiple versions of the microcode for a specific processor are available from different
files, keep the one with the highest revision level. This is the default mode of operation.
--strict-checks
Perform strict checks on the microcode data. It will refuse to load microcodes and microcode data
files with unexpected size and metadata. It will also refuse to load microcode entries that have
the same metadata, but different payload. This is the default mode of operation.
--no-strict-checks
Perform less strict checks on the microcode data. Use only if you happen to come across a
microcode data file that has microcodes with weird sizes inside, or to load microcodes from a
truncated microcode data file (in which case you will also need the --ignore-broken option).
--ignore-broken
Skip broken microcode entries during load, instead of aborting execution.
--no-ignore-broken
Abort program execution if a broken microcode is found during load. This is the default mode of
operation.
-s ! | [!]signature[,pf_mask]
Select microcodes by the specified signature and processor flags mask (pf_mask). If pf_mask is
specified, it will select only microcodes that are suitable for at least one of the processor flag
combinations in the mask.
Specify more than once to select more microcodes. This option can be combined with the --scan-
system option to select more microcodes. If signature is prefixed with a !, it will unselect
microcodes instead. Ordering matters, with later -s options overriding earlier ones.
The special notation -s! (with no signature parameter) instructs iucode-tool to require explicit
inclusion of microcode signatures (using the non-negated form of -s, or using --scan-system).
The --scan-system option has precedence, therefore the microcodes it selects cannot be unselected.
-S, --scan-system
Select microcodes by scanning all online processors on this system for their signatures.
This option can be combined with the -s option to select more microcodes.
Should the scan fail, the program will print a warning to the user and continue as if --scan-
system had not been specified.
--date-before=YYYY-MM-DD and --date-after=YYYY-MM-DD
Limit the selected microcodes by a date range. The date must be given in ISO format, with four
digits for the year and two digits for the month and day and - for the separator. Dates are not
range-checked, so you can use --date-after=2000-00-00 to select all microcodes dated since January
1st, 2000.
--loose-date-filtering
When a date range is specified, all revisions of the microcode will be considered for selection
(ignoring just the date range, all other filters still apply) should any of the microcode's
revisions be within the date range.
--strict-date-filtering
When a date range is specified, select only microcodes which are within the date range. This is
the default mode of operation.
-l, --list
List selected microcode signatures.
-L, --list-all
List all microcode signatures while they're being processed.
-k[device], --kernel[=device]
Upload selected microcodes to the kernel. Optionally, the device path can be specified (default:
/dev/cpu/microcode). This update method is being deprecated.
-K[directory], --write-firmware[=directory]
Write selected microcodes with the filenames expected by the Linux kernel firmware loader.
Optionally, the destination directory can be specified (default: /lib/firmware/intel-ucode).
-wfile, --write-to=file
Write selected microcodes to a file in binary format.
--write-earlyfw=file
Write selected microcodes to an early initramfs archive, which should be prepended to the regular
initramfs to allow the kernel to update processor microcode very early during system boot.
-Wdirectory, --write-named-to=file
Write selected microcodes to the specified directory, one microcode per file, in binary format.
The file names reflect the microcode signature, mask and revision.
--overwrite
Remove the destination file before writing. Without this option, iucode_tool will abort if the
file already exists. Do note that it will remove non-directory symlinks instead of following
them, and that it will also break any hardlinks before writing the output file.
--no-overwrite
Abort if the destination file already exists. This is the default mode of operation. Do note
that iucode_tool does not follow symlinks when writing files.
NOTES
iucode_tool reads all data to memory before doing any processing.
iucode_tool's selected microcode listing and microcode output files are sorted by cpu signature, however
the ordering inside a group of microcodes that share the same cpu signature is undefined: it is
deterministic, but it is sensitive to command line parameters and their ordering, and also depends on the
ordering of the individual microcodes inside each loaded data file.
When multiple revisions of a microcode are selected, the older ones will be skipped. Only the newest
selected revision of a microcode (or the last one in load order when the --downgrade option is active)
will be written to a file or uploaded to the kernel.
Intel microcode data files, both in binary and text formats, can be concatenated to generate a bigger and
still valid microcode data file.
iucode_tool does not follow symlinks when writing microcode data files. It will either refuse to write
the file and abort (default mode of operation), or (when the --overwrite option is active) it will remove
the target symlink or file (and therefore breaking hardlinks) before writing the new file.
iucode_tool does follow directory symlinks to locate the directory to write files into.
Linux Notes
The cpuid kernel driver is required for the --scan-system functionality to work.
Early initramfs support for microcode updates is available since Linux v3.9. Kernels without early
initramfs support will just make the microcode file available to the initramfs environment at
/kernel/x86/microcode/GenuineIntel.bin.
Each Intel processor microcode must be uploaded through a single write syscall to /dev/cpu/microcode, but
more than one microcode can be uploaded per write syscall. Writing the microcode to the kernel device
will update all system processor cores at once. This method is being deprecated and does not work on
other system processor types.
The old Linux firmware interface for microcode updates needs to be triggered on a per-core basis, by
writing the number 1 to /sys/devices/system/cpu/*/microcode/reload. Depending on kernel version, you
must either trigger it on every core to avoid a dangerous situation where some cores are using outdated
microcode, or the kernel will accept the request only for the boot processor and use it to trigger an
update on all system processor cores.
Since Linux v3.6, the per-core interface has been replaced with a new interface that explicitly triggers
an update for every core at once when the number 1 is written to
/sys/devices/system/cpu/microcode/reload.
The microcode driver should not be unloaded unless you are sure it is not going to be needed. The driver
needs to be loaded in order for the kernel to reapply the microcode updates after the system resumes from
suspend or hibernation, and also to update any system processor cores that were off-line at the time the
update was applied.
EXAMPLES
Updating files in /lib/firmware/intel-ucode:
iucode_tool -K/lib/firmware/intel-ucode /lib/firmware/intel-ucode/* /tmp/file-with-new-
microcodes.bin
Processing several compressed files at once:
zcat intel-microcode*.dat.gz | iucode-tool -k -
zcat intel-microcode*.bin.gz | iucode-tool -k -tb -
BUGS
iucode_tool will waste space when writing microcodes with extended signatures (one copy per signature).
The extended signature code is completely untested, and likely buggy. Intel so far has never distributed
microcode data files using the extended signatures.
Microcode with negative revision numbers is not special-cased, and will not be preferred over regular
microcode.
Files are not replaced atomically: if iucode_tool is interrupted while writing to a file, that file will
be corrupted.
SEE ALSO
The Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 3A: System Programming Guide,
Part 1 (order number 253668), section 9.11.
AUTHOR
Henrique de Moraes Holschuh <hmh@hmh.eng.br>
IUCODE_TOOL 1.0.1 November 24th, 2013 IUCODE_TOOL(8)