用户空间文件系统（Filesystem in Userspace，简称FUSE）是操作系统中的概念，指完全在用户态实现的文件系统。
Linux “mount”命令支持 FUSE，所以我们会看到一些基于FUSE的工具，比如sshfs，ftpfs，可以把远程mount成一个磁盘目录来操作。
hadoop中的分布式文件系统hdfs，也提供了fuse-dfs（hadoop\hadoop-hdfs-project\hadoop-hdfs\src\main\native\fuse-dfs）。
下面是fuse_dfs.c，重点句加粗。
#include "fuse_dfs.h"
#include "fuse_options.h"
#include "fuse_impls.h"
#include "fuse_init.h"
#include "fuse_connect.h"
#include
#include
#include
int is_protected(const char *path) {
dfs_context *dfs = (dfs_context*)fuse_get_context()->private_data;
assert(dfs != NULL);
assert(dfs->protectedpaths);
int i ;
for (i = 0; dfs->protectedpaths[i]; i++) {
if (strcmp(path, dfs->protectedpaths[i]) == 0) {
return 1;
}
}
return 0;
}
static struct fuse_operations dfs_oper = {
.getattr = dfs_getattr,
.access = dfs_access,
.readdir = dfs_readdir,
.destroy = dfs_destroy,
.init = dfs_init,
.open = dfs_open,
.read = dfs_read,
.symlink = dfs_symlink,
.statfs = dfs_statfs,
.mkdir = dfs_mkdir,
.rmdir = dfs_rmdir,
.rename = dfs_rename,
.unlink = dfs_unlink,
.release = dfs_release,
.create = dfs_create,
.write = dfs_write,
.flush = dfs_flush,
.mknod = dfs_mknod,
.utimens = dfs_utimens,
.chmod = dfs_chmod,
.chown = dfs_chown,
.truncate = dfs_truncate,
};
int main(int argc, char *argv[])
{
int ret;
umask(0);
extern const char *program;
program = argv[0];
struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
memset(&options, 0, sizeof(struct options));
options.rdbuffer_size = 10*1024*1024;
options.attribute_timeout = 60;
options.entry_timeout = 60;
if (-1 == fuse_opt_parse(&args, &options, dfs_opts, dfs_options)) {
return -1;
}
if (!options.private) {
fuse_opt_add_arg(&args, "-oallow_other");
}
if (!options.no_permissions) {
fuse_opt_add_arg(&args, "-odefault_permissions");
}
if (options.read_only) {
fuse_opt_add_arg(&args, "-r");
}
{
char buf[80];
snprintf(buf, sizeof buf, "-oattr_timeout=%d",options.attribute_timeout);
fuse_opt_add_arg(&args, buf);
snprintf(buf, sizeof buf, "-oentry_timeout=%d",options.entry_timeout);
fuse_opt_add_arg(&args, buf);
}
if (options.nn_uri == NULL) {
print_usage(argv[0]);
exit(EXIT_SUCCESS);
}
ret = fuse_main(args.argc, args.argv, &dfs_oper, NULL);
fuse_opt_free_args(&args);
return ret;
}
当然他的具体实现，是通过libhdfs（hadoop\hadoop-hdfs-project\hadoop-hdfs\src\main\native\libhdfs）完成的，libhdfs是hadoop的c访问接口，也可以说是jndi访问接口。
总体来说，重写fuse_operations，可以扩展mount其他东西。
windows版本的FUSE，是。