blog/Broken_umask_handling_with_sshfs.html

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
   2         "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
   3 <html>
   4  <head>
   5   <title>Petter Reinholdtsen: Broken umask handling with sshfs</title>
   6   <link rel="stylesheet" type="text/css" media="screen" href="http://people.skolelinux.org/pere/blog/style.css">
   7  </head>
   8  <body>
   9
  10  <div class="title">
  11   <h1>
  12        <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
  13
  14   </h1>
  15
  16  </div>
  17
  18
  19  <div class="entry">
  20   <div class="title">Broken umask handling with sshfs</div>
  21   <div class="date">2010-08-26 13:30</div>
  22   <div class="body">
  23 <p>My file system sematics program
  24 <a href="http://people.skolelinux.org/pere/blog/Testing_if_a_file_system_can_be_used_for_home_directories___.html">presented
  25 a few days ago</a> is very useful to verify that a file system can
  26 work as a unix home directory,and today I had to extend it a bit.  I'm
  27 looking into alternatives for home directory access here at the
  28 University of Oslo, and one of the options is sshfs.  My friend
  29 Finn-Arne mentioned a while back that they had used sshfs with Debian
  30 Edu, but stopped because of problems.  I asked today what the problems
  31 where, and he mentioned that sshfs failed to handle umask properly.
  32 Trying to detect the problem I wrote this addition to my fs testing
  33 script:</p>
  34
  35 <pre>
  36 mode_t touch_get_mode(const char *name, mode_t mode) {
  37   mode_t retval = 0;
  38   int fd = open(name, O_RDWR|O_CREAT|O_LARGEFILE, mode);
  39   if (-1 != fd) {
  40     unlink(name);
  41     struct stat statbuf;
  42     if (-1 != fstat(fd, &statbuf)) {
  43       retval = statbuf.st_mode & 0x1ff;
  44     }
  45     close(fd);
  46   }
  47   return retval;
  48 }
  49
  50 /* Try to detect problem discovered using sshfs */
  51 int test_umask(void) {
  52   printf("info: testing umask effect on file creation\n");
  53
  54   mode_t orig_umask = umask(000);
  55   mode_t newmode;
  56   if (0666 != (newmode = touch_get_mode("foobar", 0666))) {
  57     printf("  error: Wrong file mode %o when creating using mode 666 and umask 000\n",
  58            newmode);
  59   }
  60   umask(007);
  61   if (0660 != (newmode = touch_get_mode("foobar", 0666))) {
  62     printf("  error: Wrong file mode %o when creating using mode 666 and umask 007\n",
  63            newmode);
  64   }
  65
  66   umask (orig_umask);
  67   return 0;
  68 }
  69
  70 int main(int argc, char **argv) {
  71   [...]
  72   test_umask();
  73   return 0;
  74 }
  75 </pre>
  76
  77 <p>Sure enough.  On NFS to a netapp, I get this result:</p>
  78
  79 <pre>
  80 Testing POSIX/Unix sematics on file system
  81 info: testing symlink creation
  82 info: testing subdirectory creation
  83 info: testing fcntl locking
  84   Read-locking 1 byte from 1073741824
  85   Read-locking 510 byte from 1073741826
  86   Unlocking 1 byte from 1073741824
  87   Write-locking 1 byte from 1073741824
  88   Write-locking 510 byte from 1073741826
  89   Unlocking 2 byte from 1073741824
  90 info: testing umask effect on file creation
  91 </pre>
  92
  93 <p>When mounting the same directory using sshfs, I get this
  94 result:</p>
  95
  96 <pre>
  97 Testing POSIX/Unix sematics on file system
  98 info: testing symlink creation
  99 info: testing subdirectory creation
 100 info: testing fcntl locking
 101   Read-locking 1 byte from 1073741824
 102   Read-locking 510 byte from 1073741826
 103   Unlocking 1 byte from 1073741824
 104   Write-locking 1 byte from 1073741824
 105   Write-locking 510 byte from 1073741826
 106   Unlocking 2 byte from 1073741824
 107 info: testing umask effect on file creation
 108   error: Wrong file mode 644 when creating using mode 666 and umask 000
 109   error: Wrong file mode 640 when creating using mode 666 and umask 007
 110 </pre>
 111
 112 <p>So, I can conclude that sshfs is better than smb to a Netapp or a
 113 Windows server, but not good enough to be used as a home
 114 directory.</p>
 115
 116 <p>Update 2010-08-26: Reported the issue in
 117 <a href="http://bugs.debian.org/594498">BTS report #594498</a></p>
 118
 119 <p>Update 2010-08-27: Michael Gebetsroither report that he found the
 120 script so useful that he created a GIT repository and stored it in
 121 <a href="http://github.com/gebi/fs-test">http://github.com/gebi/fs-test</a>.</p>
 122 </div>
 123
 124   <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>
 125
 126   </div>
 127
 128
 129
 130
 131
 132
 133 <div id="sidebar">
 134
 135 <h2>Archive</h2>
 136 <ul>
 137
 138 <li>2010
 139 <ul>
 140
 141 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/01/">January (2)</a></li>
 142
 143 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/02/">February (1)</a></li>
 144
 145 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/03/">March (3)</a></li>
 146
 147 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/04/">April (3)</a></li>
 148
 149 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/05/">May (9)</a></li>
 150
 151 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/06/">June (14)</a></li>
 152
 153 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/07/">July (12)</a></li>
 154
 155 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/08/">August (13)</a></li>
 156
 157 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/09/">September (7)</a></li>
 158
 159 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/10/">October (9)</a></li>
 160
 161 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/11/">November (10)</a></li>
 162
 163 </ul></li>
 164
 165 <li>2009
 166 <ul>
 167
 168 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/01/">January (8)</a></li>
 169
 170 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/02/">February (8)</a></li>
 171
 172 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/03/">March (12)</a></li>
 173
 174 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/04/">April (10)</a></li>
 175
 176 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/05/">May (9)</a></li>
 177
 178 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/06/">June (3)</a></li>
 179
 180 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/07/">July (4)</a></li>
 181
 182 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/08/">August (3)</a></li>
 183
 184 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/09/">September (1)</a></li>
 185
 186 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/10/">October (2)</a></li>
 187
 188 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/11/">November (3)</a></li>
 189
 190 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/12/">December (3)</a></li>
 191
 192 </ul></li>
 193
 194 <li>2008
 195 <ul>
 196
 197 <li><a href="http://people.skolelinux.org/pere/blog/archive/2008/11/">November (5)</a></li>
 198
 199 <li><a href="http://people.skolelinux.org/pere/blog/archive/2008/12/">December (7)</a></li>
 200
 201 </ul></li>
 202
 203 </ul>
 204
 205
 206
 207 <h2>Tags</h2>
 208 <ul>
 209
 210  <li><a href="http://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer (12)</a></li>
 211
 212  <li><a href="http://people.skolelinux.org/pere/blog/tags/amiga">amiga (1)</a></li>
 213
 214  <li><a href="http://people.skolelinux.org/pere/blog/tags/aros">aros (1)</a></li>
 215
 216  <li><a href="http://people.skolelinux.org/pere/blog/tags/bootsystem">bootsystem (10)</a></li>
 217
 218  <li><a href="http://people.skolelinux.org/pere/blog/tags/debian">debian (42)</a></li>
 219
 220  <li><a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu (50)</a></li>
 221
 222  <li><a href="http://people.skolelinux.org/pere/blog/tags/english">english (71)</a></li>
 223
 224  <li><a href="http://people.skolelinux.org/pere/blog/tags/fiksgatami">fiksgatami (1)</a></li>
 225
 226  <li><a href="http://people.skolelinux.org/pere/blog/tags/fildeling">fildeling (11)</a></li>
 227
 228  <li><a href="http://people.skolelinux.org/pere/blog/tags/kart">kart (5)</a></li>
 229
 230  <li><a href="http://people.skolelinux.org/pere/blog/tags/ldap">ldap (8)</a></li>
 231
 232  <li><a href="http://people.skolelinux.org/pere/blog/tags/lenker">lenker (4)</a></li>
 233
 234  <li><a href="http://people.skolelinux.org/pere/blog/tags/ltsp">ltsp (1)</a></li>
 235
 236  <li><a href="http://people.skolelinux.org/pere/blog/tags/multimedia">multimedia (10)</a></li>
 237
 238  <li><a href="http://people.skolelinux.org/pere/blog/tags/norsk">norsk (90)</a></li>
 239
 240  <li><a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug (113)</a></li>
 241
 242  <li><a href="http://people.skolelinux.org/pere/blog/tags/opphavsrett">opphavsrett (18)</a></li>
 243
 244  <li><a href="http://people.skolelinux.org/pere/blog/tags/personvern">personvern (25)</a></li>
 245
 246  <li><a href="http://people.skolelinux.org/pere/blog/tags/reprap">reprap (10)</a></li>
 247
 248  <li><a href="http://people.skolelinux.org/pere/blog/tags/robot">robot (4)</a></li>
 249
 250  <li><a href="http://people.skolelinux.org/pere/blog/tags/rss">rss (1)</a></li>
 251
 252  <li><a href="http://people.skolelinux.org/pere/blog/tags/sikkerhet">sikkerhet (18)</a></li>
 253
 254  <li><a href="http://people.skolelinux.org/pere/blog/tags/sitesummary">sitesummary (3)</a></li>
 255
 256  <li><a href="http://people.skolelinux.org/pere/blog/tags/standard">standard (16)</a></li>
 257
 258  <li><a href="http://people.skolelinux.org/pere/blog/tags/stavekontroll">stavekontroll (1)</a></li>
 259
 260  <li><a href="http://people.skolelinux.org/pere/blog/tags/video">video (15)</a></li>
 261
 262  <li><a href="http://people.skolelinux.org/pere/blog/tags/vitenskap">vitenskap (1)</a></li>
 263
 264  <li><a href="http://people.skolelinux.org/pere/blog/tags/web">web (13)</a></li>
 265
 266 </ul>
 267
 268 </div>
 269  </body>
 270 </html>