A few years ago, I was involved in a project planning to use -Windows file servers as home directory servers for Debian -Edu/Skolelinux machines. This was thought to be no problem, as the -access would be through the SMB network file system protocol, and we -knew other sites used SMB with unix and samba as the file server to -mount home directories without any problems. But, after months of -struggling, we had to conclude that our goal was impossible.
- -The reason is simply that while SMB can be used for home -directories when the file server is Samba running on Unix, this only -work because of Samba have some extensions and the fact that the -underlying file system is a unix file system. When using a Windows -file server, the underlying file system do not have POSIX semantics, -and several programs will fail if the users home directory where they -want to store their configuration lack POSIX semantics.
- -As part of this work, I wrote a small C program I want to share -with you all, to replicate a few of the problematic applications (like -OpenOffice.org and GCompris) and see if the file system was working as -it should. If you find yourself in spooky file system land, it might -help you find your way out again. This is the fs-test.c source:
- -
-/*
- * Some tests to check the file system sematics. Used to verify that
- * CIFS from a windows server do not work properly as a linux home
- * directory.
- * License: GPL v2 or later
- *
- * needs libsqlite3-dev and build-essential installed
- * compile with: gcc -Wall -lsqlite3 -DTEST_SQLITE fs-test.c -o fs-test
-*/
-
-#define _FILE_OFFSET_BITS 64
-#define _LARGEFILE_SOURCE 1
-#define _LARGEFILE64_SOURCE 1
-
-#define _GNU_SOURCE /* for asprintf() */
-
-#include <errno.h>
-#include <fcntl.h>
-#include <stdio.h>
-#include <string.h>
-#include <stdlib.h>
-#include <sys/file.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#ifdef TEST_SQLITE
-/*
- * Test sqlite open, as done by gcompris require the libsqlite3-dev
- * package and linking with -lsqlite3. A more low level test is
- * below.
- * See also <URL: http://www.sqlite.org./faq.html#q5 >.
- */
-#include <sqlite3.h>
-#define CREATE_TABLE_USERS \
- "CREATE TABLE users (user_id INT UNIQUE, login TEXT, lastname TEXT, firstname TEXT, birthdate TEXT, class_id INT ); "
-int test_sqlite_open(void) {
- char *zErrMsg;
- char *name = "testsqlite.db";
- sqlite3 *db=NULL;
- unlink(name);
- int rc = sqlite3_open(name, &db);
- if( rc ){
- printf("error: sqlite open of %s failed: %s\n", name, sqlite3_errmsg(db));
- sqlite3_close(db);
- return -1;
- }
-
- /* create tables */
- rc = sqlite3_exec(db,CREATE_TABLE_USERS, NULL, 0, &zErrMsg);
- if( rc != SQLITE_OK ){
- printf("error: sqlite table create failed: %s\n", zErrMsg);
- sqlite3_close(db);
- return -1;
- }
- printf("info: sqlite worked\n");
- sqlite3_close(db);
- return 0;
-}
-#endif /* TEST_SQLITE */
-
-/*
- * Demonstrate locking issue found in gcompris using sqlite3. This
- * work with ext3, but not with cifs server on Windows 2003. This is
- * done in the sqlite3 library.
- * See also
- * <URL:http://www.cygwin.com/ml/cygwin/2001-08/msg00854.html> and the
- * POSIX specification
- * <URL:http://www.opengroup.org/onlinepubs/009695399/functions/fcntl.html>.
- */
-int test_gcompris_locking(void) {
- struct flock fl;
- char *name = "testsqlite.db";
- unlink(name);
- int fd = open(name, O_RDWR|O_CREAT|O_LARGEFILE, 0644);
- printf("info: testing fcntl locking\n");
-
- fl.l_whence = SEEK_SET;
- fl.l_pid = getpid();
- printf(" Read-locking 1 byte from 1073741824");
- fl.l_start = 1073741824;
- fl.l_len = 1;
- fl.l_type = F_RDLCK;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- printf(" Read-locking 510 byte from 1073741826");
- fl.l_start = 1073741826;
- fl.l_len = 510;
- fl.l_type = F_RDLCK;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- printf(" Unlocking 1 byte from 1073741824");
- fl.l_start = 1073741824;
- fl.l_len = 1;
- fl.l_type = F_UNLCK;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- printf(" Write-locking 1 byte from 1073741824");
- fl.l_start = 1073741824;
- fl.l_len = 1;
- fl.l_type = F_WRLCK;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- printf(" Write-locking 510 byte from 1073741826");
- fl.l_start = 1073741826;
- fl.l_len = 510;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- printf(" Unlocking 2 byte from 1073741824");
- fl.l_start = 1073741824;
- fl.l_len = 2;
- fl.l_type = F_UNLCK;
- if (0 != fcntl(fd, F_SETLK, &fl) ) printf(" - error!\n"); else printf("\n");
-
- close(fd);
- return 0;
-}
-
-/*
- * Test if permissions of freshly created directories allow entries
- * below them. This was a problem with OpenOffice.org and gcompris.
- * Mounting with option 'sync' seem to solve this problem while
- * slowing down file operations.
- */
-int test_subdirectory_creation(void) {
-#define LEVELS 5
- char *path = strdup("test");
- char *dirs[LEVELS];
- int level;
- printf("info: testing subdirectory creation\n");
- for (level = 0; level < LEVELS; level++) {
- char *newpath = NULL;
- if (-1 == mkdir(path, 0777)) {
- printf(" error: Unable to create directory '%s': %s\n",
- path, strerror(errno));
- break;
- }
- asprintf(&newpath, "%s/%s", path, "test");
- free(path);
- path = newpath;
- }
- return 0;
-}
-
-/*
- * Test if symlinks can be created. This was a problem detected with
- * KDE.
- */
-int test_symlinks(void) {
- printf("info: testing symlink creation\n");
- unlink("symlink");
- if (-1 == symlink("file", "symlink"))
- printf(" error: Unable to create symlink\n");
- return 0;
-}
-
-int main(int argc, char **argv) {
- printf("Testing POSIX/Unix sematics on file system\n");
- test_symlinks();
- test_subdirectory_creation();
-#ifdef TEST_SQLITE
- test_sqlite_open();
-#endif /* TEST_SQLITE */
- test_gcompris_locking();
- return 0;
-}
-
-
-When everything is working, it should print something like -this:
- --Testing POSIX/Unix sematics on file system -info: testing symlink creation -info: testing subdirectory creation -info: sqlite worked -info: testing fcntl locking - Read-locking 1 byte from 1073741824 - Read-locking 510 byte from 1073741826 - Unlocking 1 byte from 1073741824 - Write-locking 1 byte from 1073741824 - Write-locking 510 byte from 1073741826 - Unlocking 2 byte from 1073741824 -- -
I do not remember the exact details of the problems we saw, but one -of them was with locking, where if I remember correctly, POSIX allow a -read-only lock to be upgraded to a read-write lock without unlocking -the read-only lock (while Windows do not). Another was a bug in the -CIFS/SMB client implementation in the Linux kernel where directory -meta information would be wrong for a fraction of a second, making -OpenOffice.org fail to create its deep directory tree because it was -not allowed to create files in its freshly created directory.
- -Anyway, here is a nice tool for your tool box, might you never need -it. :)
+For ca. et og et halvt år siden +startet +jeg på et kart over overvåkningskamera i Norge, i regi av +personvernforeningen. Det har +blitt oppdatert regelmessing, og jeg oppdaterte det nettopp. Fra den +spede start med 22 kamera registrert er det nå registrert 54 kamera. +Det er bare en brøkdel av de kamera som finnes i Norge, men det går +sakte men sikkert i riktig retning.
+ +Informasjonen registreres fortsatt direkte inn i +OpenStreetmap, og hentes +automatisk over i + +når jeg kjører et script for å filtrere ut overvåkningskamera fra +OSM-dumpen for Norge.