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Category: OS

Operating System

OSX Yosemite cannot boot when TRIM is enabled on third-party SSD

After upgrading my MBP to OSX Yosemite and enabling TRIM, the computer cannot boot into the system after restart. It stuck with a no-entry sign.

You can solve this issue by following instructions from http://www.cindori.org/trim-in-os-x-yosemite/

Boot your Mac in Recovery Mode by holding Cmd-R during boot

Open the Terminal from the menu bar

Run these commands, replacing YourDisk with the name of your Mac disk

rm -rf /Volumes/YourDisk/System/Library/Extensions/IOAHCIFamily.kext
cp -r /System/Library/Extensions/IOAHCIFamily.kext /Volumes/YourDisk/System/Library/Extensions/IOAHCIFamily.kext
touch /Volumes/YourDisk/System/Library/Extensions
kextcache -u /Volumes/YourDisk

For me, I have to first use the disk utility to unlock my SSD first since I have Filevault enabled, otherwise the first command above will complain about “readonly” files.

Since TRIM is very helpful for SSDs, it’s encouraged to have it enabled for better performance. You can use Trim Enabler v3.2.5 and above without issues. But note that it disables kext signing on your mac, “it still leaves you with the same amount of security as in OS X Mavericks, where the kext signing requirement didn’t exist”. (http://www.cindori.org/update-on-trim-in-yosemite/)

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mod_wsgi and mod_xsendfile on OS X 10.9 Mavericks

Updated on Nov 4, 2013: The following tricks may still work, however I have found a much easier solution. Simply install Xcode command line developer tools and you should be able to compile source code without issues:

$ xcode-select --install

After upgrading my Mac from 10.8 to 10.9 Mavericks my apache stopped working, so I have to reinstall mod_wsgi and mod_xsendfile. However, tricks are needed to compile and install these mods successfully.

Upgrade Xcode

Upgrade Xcode in App Store. As mentioned by Valerie:

I had to manually upgrade Xcode (after Mavericks upgrade) from the App Store & agree to its license because ./configure hung forever until I did that.

mod_wsgi

For mod_wsgi installation, create a soft link to OSX10.9.xctoolchain:

cd /Applications/Xcode.app/Contents/Developer/Toolchains/
sudo ln -s XcodeDefault.xctoolchain OSX10.9.xctoolchain

Then run configure under mod_wsgi source code directory:

mod_wsgi-3.4$ ./configure

It will generate a Makefile similar as follows:

#  Copyright 2007 GRAHAM DUMPLETON                                               
#                                                                                
#  Licensed under the Apache License, Version 2.0 (the "License");               
#  you may not use this file except in compliance with the License.              
#  You may obtain a copy of the License at                                       
#                                                                                
#      http://www.apache.org/licenses/LICENSE-2.0                                
#                                                                                
#  Unless required by applicable law or agreed to in writing, software           
#  distributed under the License is distributed on an "AS IS" BASIS,             
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.      
#  See the License for the specific language governing permissions and           
#  limitations under the License.                                                

APXS = /usr/sbin/apxs                                                            
PYTHON = /usr/local/bin/python                                                   

DESTDIR =                                                                        
LIBEXECDIR = /usr/libexec/apache2                                                

CPPFLAGS =  -I/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/include/python2.7 -DNDEBUG 
CFLAGS =   -Wc,'-arch x86_64'                                                    
LDFLAGS =  -Wl,-F/usr/local/Cellar/python/2.7.5/Frameworks -framework Python -u _PyMac_Error   -arch x86_64
LDLIBS =  -ldl  -framework CoreFoundation                                        

all : mod_wsgi.la                                                                

mod_wsgi.la : mod_wsgi.c                                                         
    $(APXS) -c $(CPPFLAGS) $(CFLAGS) mod_wsgi.c $(LDFLAGS) $(LDLIBS)             

$(DESTDIR)$(LIBEXECDIR) :                                                        
    mkdir -p $@                                                                  

install : all $(DESTDIR)$(LIBEXECDIR)                                            
    $(APXS) -i -S LIBEXECDIR=$(DESTDIR)$(LIBEXECDIR) -n 'mod_wsgi' mod_wsgi.la 

clean :                                                                          
    -rm -rf .libs                                                                
    -rm -f mod_wsgi.o mod_wsgi.la mod_wsgi.lo mod_wsgi.slo mod_wsgi.loT          
    -rm -f config.log config.status                                              
    -rm -rf autom4te.cache                                                       

distclean : clean                                                                
    -rm -f Makefile Makefile.in                                                  

realclean : distclean                                                            
    -rm -f configure

However, this Makefile is not correct and running ‘make’ the compiler will complain something like:

mod_wsgi.c:34:10: fatal error: 'httpd.h' file not found

Prepend the following line to CPPFLAGS value:

-I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apr-1 -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apache2

Save the Makefile and it will look something like:

#  Copyright 2007 GRAHAM DUMPLETON                                               
#                                                                                
#  Licensed under the Apache License, Version 2.0 (the "License");               
#  you may not use this file except in compliance with the License.              
#  You may obtain a copy of the License at                                       
#                                                                                
#      http://www.apache.org/licenses/LICENSE-2.0                                
#                                                                                
#  Unless required by applicable law or agreed to in writing, software           
#  distributed under the License is distributed on an "AS IS" BASIS,             
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.      
#  See the License for the specific language governing permissions and           
#  limitations under the License.                                                

APXS = /usr/sbin/apxs                                                            
PYTHON = /usr/local/bin/python                                                   

DESTDIR =                                                                        
LIBEXECDIR = /usr/libexec/apache2                                                

CPPFLAGS =  -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apr-1 -I/Applications/Xcode. app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apache2 -I/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/include/python2.7 -DNDEBUG
CFLAGS =   -Wc,'-arch x86_64'                                                             
LDFLAGS =  -Wl,-F/usr/local/Cellar/python/2.7.5/Frameworks -framework Python -u _PyMac_Error   -arch x86_64
LDLIBS =  -ldl  -framework CoreFoundation                                        

all : mod_wsgi.la                                                                

mod_wsgi.la : mod_wsgi.c                                                         
    $(APXS) -c $(CPPFLAGS) $(CFLAGS) mod_wsgi.c $(LDFLAGS) $(LDLIBS)             

$(DESTDIR)$(LIBEXECDIR) :                                                        
    mkdir -p $@                                                                  

install : all $(DESTDIR)$(LIBEXECDIR)                                            
    $(APXS) -i -S LIBEXECDIR=$(DESTDIR)$(LIBEXECDIR) -n 'mod_wsgi' mod_wsgi.la 

clean :                                                                          
    -rm -rf .libs                                                                
    -rm -f mod_wsgi.o mod_wsgi.la mod_wsgi.lo mod_wsgi.slo mod_wsgi.loT          
    -rm -f config.log config.status                                              
    -rm -rf autom4te.cache                                                       

distclean : clean                                                                
    -rm -f Makefile Makefile.in                                                  

realclean : distclean                                                            
    -rm -f configure

Then make && install:

mod_wsgi-3.4$ make
mod_wsgi-3.4$ sudo make install

Modify /etc/apache2/httpd.conf to enable mod_wsgi:

LoadModule wsgi_module libexec/apache2/mod_wsgi.so

mod_xsendfile

Use the following command to compile and install mod_xsendfile:

sudo apxs -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apr-1 -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/apache2 -cia mod_xsendfile.c

Enabling HTTPS/SSL

After upgrading OS X the apache configuration was reset, but your original config is save to /etc/apache2/httpd.conf.pre-update. I need to enable SSL in httpd.conf again by uncommenting the following line:

# Include /private/etc/apache2/extra/httpd-ssl.conf

Restart Apache and everything should work fine

sudo apachectl restart
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Solution: dd too slow on Mac OS X

When I was cloning SD cards on Mac OS X using `dd’, it takes ages to get things done. I was using the following command:

diskutil unmountDisk /dev/disk2
sudo dd bs=1m if=~/Downloads/2013-10-09.alice.img of=/dev/disk2

It takes much less time when using /dev/rdisk2 instead of /dev/disk2:

diskutil unmountDisk /dev/disk2
sudo dd bs=1m if=~/Downloads/2013-10-09.alice.img of=/dev/rdisk2

The reason is that rdisks are “raw” thus resulting in a higher R/W speed, according to `man hdiutil` [1]:

/dev/rdisk nodes are character-special devices, but are “raw” in the BSD sense and force block-aligned I/O. They are closer to the physical disk than the buffer cache. /dev/disk nodes, on the other hand, are buffered block-special devices and are used primarily by the kernel’s filesystem code.

[1] http://superuser.com/questions/631592/mac-osx-why-is-dev-rdisk-20-times-faster-than-dev-disk

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A “normal” sed on Mac

The `sed` program on Mac is not a standard (GNU) one. To get the normal one, use brew:

brew install gnu-sed

After this, alter PATH. For example, add the following line to your `~/.bash_profile`:

PATH="/usr/local/opt/gnu-sed/libexec/gnubin:$PATH"

And now you have a normal sed!

 

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Installing mod_xsendfile on OS X Lion

First download mod_xsendfile.c from https://tn123.org/mod_xsendfile/

Then compile and install it:

sudo apxs -cia mod_xsendfile.c

Add the following line to /etc/apache2/httpd.conf at the end of the first block of “Load” statements:

LoadModule xsendfile_module libexec/apache2/mod_xsendfile.so

At last, restart the apache server

sudo apachectl restart

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XBMC and OS X firewall permission popups

I installed XBMC on my Mac OS X Lion and every time I open up the program, a firewall permission dialog pops up. It didn’t help even if I added the XBMC in my firewall configurations. Popups still show up. This link solves the problem neatly — You can generate a certificate and sign the program by yourself. After that the frustrating dialog should appear only once (at most). In case the link becomes invalid, here’s a screenshot of the instructions. Click to see the large picture.

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Downgrade Preview in OS X Lion

I’ve had enough with the slow Preview application in Lion. After some digging I found this tutorial to downgrade the Preview in Lion to the Snow Leopard version. Basically you need to have a copy of both the Preview.app and /System/Library/PrivateFrameworks/MeshKit.framework from Snow Leopard. If you need to associate the default app to open pdf/png with the downgraded Preview, you have to delete the original Preview.app.

tar -pczf Preview.app.tar.gz /Applications/Preview.app
sudo rm -rf /Applications/Preview.app

Update: after installing OS X updates you need to remove the Preview.app again and put the SL Preview.app to /Applications/ directory.

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C a[i] vs i[a]

When following the MIT 6.828 open course, there’s one C source code discussing pointers in Exercise 4 of lab 1.

There’s one line of code in pointers.c:

3[a] = 302;

Looks weird at first sight; but TCPL says in Chapter 5.3:

In evaluating a[i], C converts it to *(a+i) immediately; the two forms are equivalent.

So: a[i] and i[a] are equvalent (if i is a constant). 🙂

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i386-jos-elf toolchain on OS X Lion

Yesterday friend and I decided to follow the MIT Operating System Engineering course together in order to get a deep understanding of OS’s. And today I started setting up the cross compling environment for the labs. At first I wanted to get the toolchain from macports, but unluckily it didn’t successfully build binutils on my Mac. As a result, I started building the toolchain from the source code, following the instructions at http://pdos.csail.mit.edu/6.828/2011/tools.html.

The programs you need for the toolchain include binutils, gcc, and gdb. For compiling gcc you also need GMP, MPFR, and MPC. The source codes are available at:

wget http://ftpmirror.gnu.org/binutils/binutils-2.21.1.tar.bz2
wget ftp://ftp.gmplib.org/pub/gmp-5.0.4/gmp-5.0.4.tar.bz2
wget http://www.mpfr.org/mpfr-current/mpfr-3.1.0.tar.bz2
wget http://www.multiprecision.org/mpc/download/mpc-0.8.2.tar.gz
wget http://ftpmirror.gnu.org/gcc/gcc-4.5.1/gcc-core-4.5.1.tar.bz2
wget http://ftpmirror.gnu.org/gdb/gdb-6.8a.tar.gz

Unzip them in a directory and build binutils, gcc, and gdb one by one.

$ tar jxvf binutils-2.21.1.tar.bz2
$ cd binutils-2.21.1
$ ./configure --target=i386-jos-elf --disable-nls && make && sudo make install

In order to build gcc, GMP, MPFR and MPC needs to be built first.

$ mkdir -p libs/install
$ mv gmp-5.0.4.tar.bz2 mpfr-3.1.0.tar.bz2 mpc-0.8.2.tar.gz libs/
$ tar jxvf gmp-5.0.4.tar.bz2
$ mkdir gmp-build; cd gmp-build
$ ../gmp-5.0.4/configure --prefix=$(cd ../install && pwd)
$ make && sudo make install
$ cd ..
$ tar jxvf mpfr-3.1.0.tar.bz2
$ mkdir mpfr-build; cd mpfr-build
$ ../mpfr-3.1.0/configure --prefix=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make && sudo make install
$ cd ..
$ tar zxvf mpc-0.8.2.tar.gz
$ mkdir mpc-build; cd mpc-build
$ ./configure --prefix=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpfr=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make ; sudo make install
$ cd ..
$ tar jxvf gcc-core-4.5.1.tar.bz2
$ mkdir gcc-build; cd gcc-build
$ ../gcc-4.5.1/configure --target=i386-jos-elf --disable-nls --without-headers --with-newlib --disable-threads --disable-shared --disable-libmudflap --disable-libssp --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpfr=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpc=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make ; sudo make install

Note that it’s essential to build gcc in a directory different from the source code directory to avoid compiling errors.

Then make gdb:

$ tar zxvf gdb-6.8a.tar.gz
$ mkdir gdb-build; cd gdb-build
$ ../gdb-6.8/./configure --target=i386-jos-elf --program-prefix=i386-jos-elf- --disable-werror
$ make && sudo make install

QEMU is available in macports:

$ sudo port install qemu
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