[Fedora-livecd-list] /etc/mtab symlink to /proc/self/mounts

[Gregory Fowler]

Hi
I use el6 based Live CDs and I think this last commit is causing the 
liveinst  anaconda scripts some headaches.  After pulling version 16.3 
of the tools from the git repo and updating my Build Host, I started 
having problems doing  install to HD from LiveCD.

Basically, anaconda included in el6 and el6u1 assumes that /etc/mtab is 
a regular file with rw attributes.
When the installer tries to open the file for writing and populate it,  
we are getting a traceback  because /etc/mtab is symlinked to 
/proc/self/mounts  and that file is not writable.

If it is necessary to symlink /etc/mtab to proc/self/mounts in the 
livecd creator tool, would it be possible to implement a fix for 
anaconda scripts that do not like seeing /etc/mtab as a link to a read 
only /proc file?



**Commit:
http://git.fedorahosted.org/git/?p=livecd;a=commit;h=9e431a9c86398705ec7b30328dc0981539e15a40

diff --git a/imgcreate/creator.py 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118> 
b/imgcreate/creator.py 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40>
index ec4c1ba 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118>..675dcf6 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40> 
100644(file)
--- a/imgcreate/creator.py 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118>
+++ b/imgcreate/creator.py 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40>
@@ -536,7 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118#l536> 
+536,7 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40#l536> 
@@ class ImageCreator(object):
          self.__create_minimal_dev()
-        os.symlink("../proc/mounts", self._instroot + "/etc/mtab")
+        os.symlink("/proc/self/mounts", self._instroot + "/etc/mtab")
          self.__write_fstab()
@@ -548,11 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118#l548> 
+548,6 
<http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40#l548> 
@@ class ImageCreator(object):
          from the install root.
          """
-        try:
-            os.unlink(self._instroot + "/etc/mtab")
-        except OSError:
-            pass
-
          self.__destroy_selinuxfs()
          self._undo_bindmounts()

**Install to HD Failure:
The failure looks like

    Traceback (most recent call first):
    File "/usr/lib/anaconda/livecd.py", line 408, in doPostInstall
    f.close()
    File "/usr/lib/anaconda/backend.py", line 239, in doPostInstall
    anaconda.backend.doPostInstall(anaconda)
    File "/usr/lib/anaconda/dispatch.py", line 208, in moveStep
    rc = stepFunc(self.anaconda)
    File "/usr/lib/anaconda/dispatch.py", line 126, in gotoNext
    self.moveStep()
    File "/usr/lib/anaconda/gui.py", line 1381, in nextClicked
    self.anaconda.dispatch.gotoNext()
    File "/usr/lib/anaconda/iw/progress_gui.py", line 79, in renderCallback
    self.intf.icw.nextClicked()
    File "/usr/lib/anaconda/gui.py", line 1402, in handleRenderCallback
    self.currentWindow.renderCallback()
    IOError: [Errno 22] Invalid argument
    ...
    IOError: [Errno 22] Invalid argument

    Local variables in innermost frame:

**Simple test:
When I echo foo into /proc/self/mounts ..
[root at bur374-199 ~]# echo foo >> /proc/self/mounts

-bash: echo: write error: Invalid argument

...Looks like the anaconda python exception.



**Workaround:
I think this file from anaconda package /usr/lib/anaconda/livecd.py , 
needs to take into account the possibility that /etc/mtab is symlinked 
to a ro file in proc and either do nothing  (patch below),  or unlink 
and create a regular file before trying to write data.

I have had to add this patch to my el6 finish scripts as a workaround.
###Finish script to fix anaconda liveinst  when /etc/mtab is symlinked
%post

cat > /tmp/apatch << EOF_patch
--- /usr/lib/anaconda/livecd.py 2011-06-10 12:53:52.141225479 -0400
+++ /usr/lib/anaconda/livecd.py_new     2011-06-10 12:57:17.190133970 -0400
@@ -403,9 +403,10 @@

          # now write out the "real" fstab and mtab
          anaconda.id.storage.write(anaconda.rootPath)
-        f = open(anaconda.rootPath + "/etc/mtab", "w+")
-        f.write(anaconda.id.storage.mtab)
-        f.close()
+       if not os.path.islink("/etc/mtab"):
+            f = open(anaconda.rootPath + "/etc/mtab", "w+")
+            f.write(anaconda.id.storage.mtab)
+            f.close()

          # copy over the modprobe.conf
          if os.path.exists("/etc/modprobe.conf"):
EOF_patch
patch -d /usr/lib/anaconda < /tmp/apatch


Thanks
Gregory Fowler
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