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+ <title>Petter Reinholdtsen: Broken umask handling with sshfs</title>
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+ <div class="title">
+ <h1>
+ <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
+
+ </h1>
+
+ </div>
+
+
+ <div class="entry">
+ <div class="title">Broken umask handling with sshfs</div>
+ <div class="date">2010-08-26 13:30</div>
+ <div class="body">
+<p>My file system sematics program
+<a href="http://people.skolelinux.org/pere/blog/Testing_if_a_file_system_can_be_used_for_home_directories___.html">presented
+a few days ago</a> is very useful to verify that a file system can
+work as a unix home directory,and today I had to extend it a bit. I'm
+looking into alternatives for home directory access here at the
+University of Oslo, and one of the options is sshfs. My friend
+Finn-Arne mentioned a while back that they had used sshfs with Debian
+Edu, but stopped because of problems. I asked today what the problems
+where, and he mentioned that sshfs failed to handle umask properly.
+Trying to detect the problem I wrote this addition to my fs testing
+script:</p>
+
+<pre>
+mode_t touch_get_mode(const char *name, mode_t mode) {
+ mode_t retval = 0;
+ int fd = open(name, O_RDWR|O_CREAT|O_LARGEFILE, mode);
+ if (-1 != fd) {
+ unlink(name);
+ struct stat statbuf;
+ if (-1 != fstat(fd, &statbuf)) {
+ retval = statbuf.st_mode & 0x1ff;
+ }
+ close(fd);
+ }
+ return retval;
+}
+
+/* Try to detect problem discovered using sshfs */
+int test_umask(void) {
+ printf("info: testing umask effect on file creation\n");
+
+ mode_t orig_umask = umask(000);
+ mode_t newmode;
+ if (0666 != (newmode = touch_get_mode("foobar", 0666))) {
+ printf(" error: Wrong file mode %o when creating using mode 666 and umask 000\n",
+ newmode);
+ }
+ umask(007);
+ if (0660 != (newmode = touch_get_mode("foobar", 0666))) {
+ printf(" error: Wrong file mode %o when creating using mode 666 and umask 007\n",
+ newmode);
+ }
+
+ umask (orig_umask);
+ return 0;
+}
+
+int main(int argc, char **argv) {
+ [...]
+ test_umask();
+ return 0;
+}
+</pre>
+
+<p>Sure enough. On NFS to a netapp, I get this result:</p>
+
+<pre>
+Testing POSIX/Unix sematics on file system
+info: testing symlink creation
+info: testing subdirectory creation
+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
+info: testing umask effect on file creation
+</pre>
+
+<p>When mounting the same directory using sshfs, I get this
+result:</p>
+
+<pre>
+Testing POSIX/Unix sematics on file system
+info: testing symlink creation
+info: testing subdirectory creation
+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
+info: testing umask effect on file creation
+ error: Wrong file mode 644 when creating using mode 666 and umask 000
+ error: Wrong file mode 640 when creating using mode 666 and umask 007
+</pre>
+
+<p>So, I can conclude that sshfs is better than smb to a Netapp or a
+Windows server, but not good enough to be used as a home
+directory.</p>
+</div>
+
+ <div class="tags">Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug</a>.</div>
+
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