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FSS(4) Device Drivers Manual FSS(4) NAME fss - file system snapshot device SYNOPSIS pseudo-device fss 4 DESCRIPTION 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). IOCTLS 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) Configures a 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) Gets the status of a 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; }; The struct element fsg_mount is the mount point of the file system. The struct element fsg_time is the time this snapshot was taken. The struct element fsg_csize is the current size of data clusters. The struct element fsg_mount_size is the number of clusters of the file system. The struct element fsg_bs_size is the number of clusters written to the backing store. FSSIOCCLR Unconfigures a fss device. FSSIOFSET(int) Sets the flags of a fss device. Possible flags are: FSS_UNCONFIG_ON_CLOSE Unconfigure the fss device on the last close. FSS_UNLINK_ON_CREATE Unlink the backing file before the fss device is created. FSSIOFGET(int) Gets the flags of a fss device. KERNEL THREADS 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. FILES /dev/rfss? /dev/fss? SEE ALSO fssconfig(8), mount(8), umount(8) HISTORY The fss device appeared in NetBSD 2.0. NetBSD 9.99 February 24, 2011 NetBSD 9.99