Re: [PATCH v2 2/2] kvm tools: Add '--rootfs' and '--binsh'

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Tue,  2 Aug 2011 21:46:29 +0300, Sasha Levin <levinsasha928@gmail.com> wrote:
> This patch adds 2 new flags:
> 
>  --rootfs [path] - Specifies a path to use as rootfs. The path will be mounted
> using virtio-9p and booted from.
> Easiest way to test it is to mount the sample image we recommend with kvm tool
> (http://wiki.qemu.org/download/linux-0.2.img.bz2) and mounting it somewhere.
> *PLEASE DO NOT TRY BOOTING FROM YOUR REAL ROOT AKA '/', EVEN WITH READ ONLY
> SET* - Lets make sure the code is bulletproof before we delete your rootfs :)
> 
>  --binsh - This flag will boot into simple /bin/sh shell instead of going
> through /sbin/init. This is usefull for more complex distribution rootfs
> where we have to deal with /etc/fstab and such.
> 
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

> ---
>  tools/kvm/builtin-run.c |   18 +++++++++++++++++-
>  1 files changed, 17 insertions(+), 1 deletions(-)
> 
> diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
> index 2e04265..78680ec 100644
> --- a/tools/kvm/builtin-run.c
> +++ b/tools/kvm/builtin-run.c
> @@ -76,11 +76,13 @@ static const char *guest_mac;
>  static const char *host_mac;
>  static const char *script;
>  static const char *guest_name;
> +static const char *rootfs;
>  static bool single_step;
>  static bool readonly_image[MAX_DISK_IMAGES];
>  static bool vnc;
>  static bool sdl;
>  static bool balloon;
> +static bool bin_sh;
>  extern bool ioport_debug;
>  extern int  active_console;
>  extern int  debug_iodelay;
> @@ -156,6 +158,8 @@ static const struct option options[] = {
>  	OPT_BOOLEAN('\0', "balloon", &balloon, "Enable virtio balloon"),
>  	OPT_BOOLEAN('\0', "vnc", &vnc, "Enable VNC framebuffer"),
>  	OPT_BOOLEAN('\0', "sdl", &sdl, "Enable SDL framebuffer"),
> +	OPT_STRING('\0', "rootfs", &rootfs, "path", "Use path as rootfs"),
> +	OPT_BOOLEAN('\0', "binsh", &bin_sh, "Boot rootfs to /bin/sh instead of /sbin/init"),
> 
>  	OPT_GROUP("Kernel options:"),
>  	OPT_STRING('k', "kernel", &kernel_filename, "kernel",
> @@ -615,7 +619,7 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>  		strlcat(real_cmdline, kernel_cmdline, sizeof(real_cmdline));
> 
>  	hi = NULL;
> -	if (!image_filename[0]) {
> +	if (!rootfs && !image_filename[0]) {
>  		hi = host_image(real_cmdline, sizeof(real_cmdline));
>  		if (hi) {
>  			image_filename[0] = hi;
> @@ -627,6 +631,18 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>  	if (!strstr(real_cmdline, "root="))
>  		strlcat(real_cmdline, " root=/dev/vda rw ", sizeof(real_cmdline));
> 
> +	if (rootfs) {
> +		char tmp[PATH_MAX];
> +
> +		if (realpath(rootfs, tmp) == 0 ||
> +		    virtio_9p__init(kvm, tmp, "/dev/root") < 0)
> +			die("Unable to initialize virtio 9p");
> +		strcat(real_cmdline, " root=/dev/root rootflags=rw,trans=virtio,version=9p2000.u rootfstype=9p");
> +
> +		if (bin_sh)
> +			strcat(real_cmdline, " init=/bin/sh");
> +	}
> +
>  	if (image_count) {
>  		kvm->nr_disks = image_count;
>  		kvm->disks    = disk_image__open_all(image_filename, readonly_image, image_count);
> -- 
> 1.7.6
>