Command line options
Command-line options generally take a set of key-value pairs separated by the comma (,) character. The acceptable key-values for each option can be obtained by passing the --help option to a crosvm command:
crosvm run --help
...
-b, --block parameters for setting up a block device.
Valid keys:
path=PATH - Path to the disk image. Can be specified
without the key as the first argument.
ro=BOOL - Whether the block should be read-only.
(default: false)
root=BOOL - Whether the block device should be mounted
as the root filesystem. This will add the required
parameters to the kernel command-line. Can only be
specified once. (default: false)
sparse=BOOL - Indicates whether the disk should support
the discard operation. (default: true)
block-size=BYTES - Set the reported block size of the
disk. (default: 512)
id=STRING - Set the block device identifier to an ASCII
string, up to 20 characters. (default: no ID)
direct=BOOL - Use O_DIRECT mode to bypass page cache.
(default: false)
...
From this help message, we see that the --block or -b option accepts the path, ro, root, sparse, block-size, id, and direct keys. Keys which default value is mentioned are optional, which means only the path key must always be specified.
One example invocation of the --block option could be:
--block path=/path/to/bzImage,root=true,block-size=4096
Keys taking a boolean parameters can be enabled by specifying their name witout any value, so the previous option can also be written as
--block path=/path/to/bzImage,root,block-size=4096
Also, the name of the first key can be entirely omitted, which further simplifies our option as:
--block /path/to/bzImage,root,block-size=4096
