FSS(4) | Device Drivers Manual | FSS(4) |
fss
— file system
snapshot device
pseudo-device fss 4
The fss
driver provides a read-only
interface to the snapshot of a currently mounted file system. Reading from a
fss
device gives the view of the file system when
the snapshot was taken. It can be configured via
ioctl(2).
The ioctl(2) command
codes below are defined in
<sys/dev/fssvar.h>
.
The (third) argument to ioctl(2) should be a pointer to the type indicated.
FSSIOCSET(struct
fss_set)
fss
device.
struct fss_set { char *fss_mount; char *fss_bstore; blksize_t fss_csize; int fss_flags; };
The struct element fss_mount is the mount point of the file system. The struct element fss_bstore is either a regular file or a raw disk device where data overwritten on the file system will be saved. The struct element fss_csize is the preferred size of this data. The struct element fss_flags is the initial set of flags.
FSSIOCGET(struct
fss_get)
fss
device.
struct fss_get { char fsg_mount[MNAMELEN]; struct timeval fsg_time; blksize_t fsg_csize; blkcnt_t fsg_mount_size; blkcnt_t fsg_bs_size; };
FSSIOCCLR
fss
device.FSSIOFSET(int)
fss
device. Possible flags
are:
FSS_UNCONFIG_ON_CLOSE
fss
device on the last
close.FSS_UNLINK_ON_CREATE
fss
device
is created.FSSIOFGET(int)
fss
device.For each active snapshot device there is a kernel thread that handles the backing store. This thread is named fssN where N is the device minor number.
The fss
device appeared in
NetBSD 2.0.
February 24, 2011 | NetBSD 10.99 |