ejg3@cornell.edu
Glibc 2 is the latest version of the GNU C Library. It currently runs unmodified on GNU Hurd systems and Linux i386, m68k, and alpha systems. Support for Linux PowerPC, MIPS, Sparc, Sparc 64, and Arm will be in version 2.1. In the future support for other architectures and operating systems will be added.
On Linux, glibc 2 is used as the libc with major version 6, the successor of the Linux libc 5. It is intended by the Linux libc developers to eventually replace libc 5. As of 2.0.6, glibc is considered production quality. Version 2.1 (due out in the near future) will be ready for main stream use along with adding more ports and features.
There are three optional add-ons available for glibc 2:
The UFC-crypt package. It is seperate because of export restrictions.
An implementation of the Posix 1003.1c "pthread" interface.
Contains the data needed to build the locale data files to use the internationalization features of the glibc.
The crypt and LinuxThreads add-ons are strongly recommended... not using them risks to be incompatible with the libraries of other systems. (If you do not wish to use them, you must add the option --disable-sanity-checks when you run configure.)
This HOWTO covers installing the glibc 2 library on an existing Linux system. It is tailored for users of Intel based systems currently using libc 5, but users of other systems and alternate libraries (such as glibc 1) should be able to use this information by substituting the proper filenames and architecture names in the appropriate places.
The latest copy of this HOWTO can be found as part of the Linux Documentation Project or from http://www.imaxx.net/~thrytis/glibc/Glibc2-HOWTO.html.
Differences between version 1.6 and 1.5:
Differences between version 1.5 and 1.4:
There are a few ways to install glibc. You can install the libraries as a test, using the existing libraries as the default but letting you try the new libraries by using different options when compiling your program. Installing in this way also makes it easy to remove glibc in the future (though any program linked with glibc will no longer work after the libraries are removed). Using glibc as a test library requires you to compile the libraries from source. There is no binary distribution for installing libraries this way. This installation is described in Installing as a test library.
The other way described in this document to install is using glibc as your primary library. All new programs that you compile on your system will use glibc, though you can link programs with your old libraries using different options while compiling. You can either install the libraries from binaries, or compile the library yourself. If you want to change optimization or configuration options, or use an add-on which is not distributed as a binary package, you must get the source distribution and compile. This installation procedure is described in Installing as the primary C library.
Frodo Looijaard describes yet another way of installing glibc. His method involves installing glibc as a secondary library and setting up a cross compiler to compile using glibc. The installation procedure for this method is more complicated then the test library install described in this document, but allows for easier compiling when linking to glibc. This method is described in his Installing glibc-2 on Linux document.
If you are currently running Debian 1.3 but do not want to upgrade to the unstable version of Debian to use glibc, the Debian libc5 to libc6 Mini-HOWTO describes how to use Debian packages to upgrade your system.
If you are installing glibc 2 on an important system, you might want to use the test install. Even if there are no bugs, some programs will need to be modified before they will compile due to changes in function prototypes and types.
The glibc 2 consists of the glibc package and three optional add-on packages, LinuxThreads, Locale, and Crypt. The source can be found at
It will take about 150 MB of disk space for the full compile and install. The basic binary install of just the core library package is about 50 MB.
Binary packages for 2.0.6 are not available. Version 2.0.4 binary packages are available for i386 and m68k, and version 2.0.1 for the alpha can be found at
If you are running a Red Hat distribution, you can get rpms for glibc 2 from ftp://ftp.redhat.com/pub/redhat/. Glibc 2 is the primary C library for the new Red Hat distribution 5.0.
If you are running a Debian distribution, you can get the packages for glibc 2 from ftp://ftp.debian.org/debian/dists/unstable/main/. The files are named libc6. Glibc 2 is now part of the base package of the hamm version of Debian, and will be the primary libc when Debian 2.0 is released.
This section covers installing glibc 2 as a test library. Anything you compile will be linked to your existing libraries unless you give some extra parameters to link to the new libraries. It appears that the paths are compiled into quite a few files, so you probably have to install the library from source.
On an i586@133 with 64 MB of RAM, it takes about 3 hours to compile with full libraries with add-ons. On a loaded i686@200, it takes about half an hour.
You need to extract the source from the archives so you can compile it. The best way to do this is:
tar xzf glibc-2.0.6.tar.gz
cd glibc-2.0.6
tar xzf ../glibc-linuxthreads-2.0.6.tar.gz
tar xzf ../glibc-crypt-2.0.6.tar.gz
tar xzf ../glibc-localedata-2.0.6.tar.gz
In the glibc-2.0.6 directory, create a directory named compile, and cd into it. All work will be done in this directory, which will simplify cleaning up. (The developers have not been very concerned with getting 'make clean' perfect yet.)
mkdir compile
cd compile
../configure. To use the add-on packages, you need to specify
them with --enable-add-ons, such as --enable-add-ons=linuxthreads,crypt,localedata.
You also need to choose a destination directory to install to.
/usr/i486-linuxglibc2 is a good choice. The configure line for this would be:
../configure --enable-add-ons=linuxthreads,crypt,localedata --prefix=/usr/i486-linuxglibc2
To compile and verify, run:
make
make check
compile/ directory):
make install
ld.so to /lib/ld-linux.so.2:
ln -s /usr/i486-linuxglibc2/lib/ld-linux.so.2 /lib/ld-linux.so.2
/lib will ease upgrading to glibc as
your primary C library when the stable version is released./etc/ld.so.conf. You need to add path to the lib
directory the new libraries reside in at the end of the file, which will
be <prefix>/lib, such as /usr/i486-linuxglibc2/lib
for the choice above. After you have modified /etc/ld.so.conf, run
ldconfig -v
The last step of installation is updating /usr/lib/gcc-lib so gcc
knows how to use the new libraries. First you need to duplicate the existing
configuration. To find out which configuration is current, use the -v
option of gcc:
% gcc -v
Reading specs from /usr/lib/gcc-lib/i486-unknown-linux/2.7.2.2/specs
gcc version 2.7.2.2
/usr/lib/gcc-lib/<system> to
the new test system directory:
cd /usr/lib/gcc-lib/
cp -r i486-unknown-linux i486-linuxglibc2
cd /usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2
specs found in this directory. In this file,
change /lib/ld-linux.so.1 to /lib/ld-linux.so.2. You also
need to remove all expressions %{...:-lgmon} in the file, since
glibc does not use the gmon library for profiling. A sample specs file can
be found in the
Sample specs file section.
You need create links in your new include directory to other include directories:
cd /usr/i486-linuxglibc2/include
ln -s /usr/src/linux/include/linux
ln -s /usr/src/linux/include/asm
ln -s /usr/X11R6/include/X11
/usr/include. (Some libraries may need to be recompiled
with glibc2 in order to work with it. In these cases, just compile and
install the package to /usr/i486-linuxglibc2.)
To test the installation, create the following program in a file glibc.c:
#include <stdio.h>
main()
{
printf("hello world!\n");
}
% gcc -b i486-linuxglibc2 -nostdinc -I/usr/i486-linuxglibc2/include -I/usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2/include glibc.c -o glibc
% ldd glibc
libc.so.6 => /usr/i486-linuxglibc2/lib/libc-2.0.6.so (0x4000d000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
This section covers installing glibc 2 as your primary C library. Any new programs you compile will be linked with this library, unless you use special compile options to link with another version.
If you are are using Redhat or Debian and have downloaded the appropriate rpm or deb files, see the Redhat or Debian installion instructions. You can then skip this section.
This section explains how to compile glibc 2 and add-ons from the sources. You must compile the library if you want to change optimization or configuration options or use a package you do not have the binaries for.
On an i586@133 with 64 MB of RAM, it takes about 3 hours to compile with full libraries with add-ons. On a loaded i686@200, it takes about half an hour.
You need to extract the source from the archives so you can compile it. The best way to do this is:
tar xzf glibc-2.0.6.tar.gz
cd glibc-2.0.6
tar xzf ../glibc-linuxthreads-2.0.6.tar.gz
tar xzf ../glibc-crypt-2.0.6.tar.gz
tar xzf ../glibc-localedata-2.0.6.tar.gz
In the glibc-2.0.6 directory, create a directory named compile, and
cd into it. All work will be done in this directory, which will simplify
cleaning up. (The developers have not been very concerned with getting 'make
clean' perfect yet.)
mkdir compile
cd compile
../configure. To use the add-on packages, you need to specify
them with --enable-add-ons, such as --enable-add-ons=linuxthreads,crypt,localedata.
You probably will also want to specify paths where it will be installed.
To match the standard linux distributions, specify --prefix=/usr. (When
a prefix of /usr is specified on a linux system, configure knows to
adjust other paths to place libc.so and other important libraries in
/lib.) The whole configure line would be:
../configure --enable-add-ons=linuxthreads,crypt,localedata --prefix=/usr
To compile and verify, run:
make
make check
Now you need to move some files around to prepare for the new library, whether you are installing from source or binaries. Any new program compiled will be linked to glibc, but old programs which are not statically linked will still depend on libc 5, so you can not just overwrite the old version.
mkdir -p /usr/i486-linuxlibc5/lib
/usr/include:
mv /usr/include /usr/i486-linuxlibc5/include
mkdir /usr/include
ln -s /usr/src/linux/include/linux /usr/include/linux
ln -s /usr/src/linux/include/asm /usr/include/asm
ln -s /usr/X11R6/include/X11 /usr/include/X11
ln -s /usr/lib/g++-include /usr/include/g++
/usr/local/g++-include, while Debian
puts the headers in /usr/include/g++, and links
/usr/lib/g++-include to /usr/include/g++. In the later
case, you probably will want to move the original g++ include directory back
to /usr/include.
/usr/include or put a link to their
include directories in the /usr/include. These files and links need
to be restored in order to use the extra libraries properly.
/usr/i486-linuxlibc5/lib) at the top of your
/etc/ld.so.conf file. You should have ld.so 1.8.8 or
better installed to avoid getting strange messages once glibc is installed.
mv /usr/lib/libbsd.a /usr/i486-linuxlibc5/lib
mv /usr/lib/libc.a /usr/i486-linuxlibc5/lib
mv /usr/lib/libgmon.a /usr/i486-linuxlibc5/lib
mv /usr/lib/libm.a /usr/i486-linuxlibc5/lib
mv /usr/lib/libmcheck.a /usr/i486-linuxlibc5/lib
mv /usr/lib/libc.so /usr/i486-linuxlibc5/lib
mv /usr/lib/libm.so /usr/i486-linuxlibc5/lib
cp /lib/libm.so.5.* /usr/i486-linuxlibc5/lib
cp /lib/libc.so.5.* /usr/i486-linuxlibc5/lib
libm.so.5 and libc.so.5 should be copied and not moved if
/usr is a seperate partition from /, because they are
required by programs used to start linux and must be located on the root
drive partition.
/usr/lib/*.o files into the new directory.
mv /usr/lib/crt1.o /usr/i486-linuxlibc5/lib
mv /usr/lib/crti.o /usr/i486-linuxlibc5/lib
mv /usr/lib/crtn.o /usr/i486-linuxlibc5/lib
mv /usr/lib/gcrt1.o /usr/i486-linuxlibc5/lib
ldconfig -v
If you are installing glibc from precompiled binaries, you first want to check what is in the package before you install the binaries:
tar -tzvvf glibc-2.0.bin.i386.tar.gz
tar -tzvvf glibc-crypt-2.0.bin.i386.tar.gz
cd /
tar -xzf glibc-2.0.bin.i386.tar.gz
tar -xzf glibc-crypt-2.0.bin.i386.tar.gz
ldconfig -v
The most recent glibc version is generally not available as a binary package, and it is strongly recommended that you run the most recent version to avoid bugs. If you can not build the library yourself, grab a binary package of glibc from one of the distributions that is based on glibc (e.g. RedHat) and install this.
To install the library from source, run as root from the compile/
directory:
make install
ldconfig -v
The final step of the installation (for both binary and source installs)
is to update the gcc specs file so you can link your programs
properly. To determine which specs file is the one used by gcc, use:
% gcc -v
reading specs from /usr/lib/gcc-lib/i486-unknown-linux/2.7.2.2/specs
gcc version 2.7.2.2
In this case, i486-unknown-linux is the system, and 2.7.2.2 is the version.
You need to copy the /usr/lib/gcc-lib/<system> to the old
system directory:
cd /usr/lib/gcc-lib/
cp -r i486-unknown-linux i486-linuxlibc5
Change into the original directory and version directory
cd /usr/lib/gcc-lib/i486-unknown-linux/2.7.2.2
and edit the file specs found in this directory. In this file,
change /lib/ld-linux.so.1 to /lib/ld-linux.so.2. You
also need to remove all expressions %{...:-lgmon} in the file,
since glibc does not use the gmon library for profiling. A sample specs
file can be found in the
Sample specs file section.
To test the installation, create the following program in a file glibc.c:
#include <stdio.h>
main()
{
printf("hello world!\n");
}
% gcc glibc.c -o glibc
% ldd glibc
libc.so.6 => /lib/libc.so.6 (0x4000e000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
There are times you will want to use an alternate library to compile your programs with. This section explains how to accomplish this, using the directories and installation names used in the examples in the previous two sections. Remember to change the names to fit your setup.
Before compiling any programs which is used in the system boot process,
remember that if the program is dynamically linked and is used before the
non-root partitions are mounted, all linked libraries must be on the root
partition. Following the installation process in the previous section
for installing glibc as your primary C library, the old libc is left in
/lib, which will be on your root partition. This means all of your
programs will still work during booting. However, if /usr is on a
different partition and you install glibc as a test library in
/usr/i486-linuxglibc2, any new programs you compile with glibc
will not work until your /usr partition is mounted.
To compile a program with a test-install glibc, you need to reset the
include paths to point to the glibc includes. Specifying
"-nostdinc" will negate the normal paths, and
"-I/usr/i486-linuxglibc2/include" will point
to the glibc includes. You will also need to specify the gcc includes,
which are found in /usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2/include
(assuming you installed the test lib in i486-linuxglibc2 with gcc version
2.7.2.2).
To link a program with a test-install glibc, you need to specify the gcc setup. This is done by using the option "-b i486-linuxglibc2".
For most programs, you can specify these new options by adding them to the
$CFLAGS and $LDFLAGS makefile options:
CFLAGS = -nostdinc -I/usr/i486-linuxglibc2/include -I/usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2/include -b i486-linuxglibc2
LDFLAGS = -b i486-linuxglibc2
$CFLAGS
and $LDFLAGS shell variables (by using env/setenv for
csh/tcsh, or set/export for sh/bash/etc) before running configure. The
makefiles generated by this should contain the proper $CFLAGS
and $LDFLAGS. Not all configure scripts
will pick up the variables, so you should check after running configure
and edit the makefiles by hand if necessary.
If the programs you are compiling only call gcc (and not cpp or binutils directly), you can use the following script to save having to specify all of the options each time:
#!/bin/bash
/usr/bin/gcc -b i486-linuxglibc2 -nostdinc \
-I/usr/i486-linuxglibc2/include \
-I/usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2/include "$@"
To compile a program with your old libraries when you have installed glibc as your main library, you need to reset the include paths to the old includes. Specifying "-nostdinc" will negate the normal paths, and "-I/usr/i486-linuxlibc5/include" will point to the glibc includes. You must also specify "-I/usr/lib/gcc-lib/i486-linuxlibc5/2.7.2.2/include" to include the gcc specific includes. Remember to adjust these paths based on the what you named the new directories and your gcc version.
To link a program with your old libc, you need to specify the gcc setup. This is done by using the option "-b i486-linuxlibc5".
For most programs, you can specify these new options by appending them
to the $CFLAGS and $LDFLAGS makefile options:
CFLAGS = -nostdinc -I/usr/i486-linuxlibc5/include -I/usr/lib/gcc-lib/i486-linuxlibc5/2.7.2.2/include -b i486-linuxlibc5
LDFLAGS = -b i486-linuxlibc5
$CFLAGS
and $LDFLAGS shell variables (by using env/setenv for
csh/tcsh, or set/export for sh/bash/etc) before running configure. The
makefiles generated by this should contain the proper
$CFLAGS and $LDFLAGS. Not all configure
scripts will pick up the variables, so you should check after running
configure and edit the makefiles by hand if necessary.
If the programs you are compiling only call gcc (and not cpp or binutils directly), you can use the following script to save having to specify all of the options each time:
#!/bin/bash
/usr/bin/gcc -b i486-linuxlibc5 -nostdinc \
-I/usr/i486-linuxlibc5/include \
-I/usr/lib/gcc-lib/i486-linuxlibc5/2.7.2.2/include "$@"
Libg++ uses parts of the math library, so is link to libm. Since your existing libg++ will be compiled with your old library, you will have to recompile libg++ with glibc or get a binary copy. The latest source for libg++ along with a binary linked with glibc (for x86) can be found at ftp://ftp.yggdrasil.com/private/hjl/.
If you have installed glibc as a test library, you need to install
the files into the directory you installed glibc into (such as
/usr/i486-linuxglibc2 for the example in the previous sections).
If you are installing from the binary package (which i would recommend,
since i never had any luck compiling libg++ this way), you need to
extract the files into a temporary directory and move all the
usr/lib/ files into the <install directory>/lib/
directory, the usr/include/ files into the
<install directory>/include/ directory (remember to
delete your include/g++ link first!), and the usr/bin/
files into the <install directory>/bin/ directory.
If you have installed glibc as the primary library, you first need to move your old libg++ files into your old libc directory if you still want to be able to compile g++ programs with your old libc. Probably the easiest way to do this is by installing a new copy of the libg++ compiled with libc 5 as in the previous section, and then installing the glibc version normally.
If you are trying to compile a C++ program with a non-primary libc, you
will need to include the g++ include dir, which in the examples above would
be /usr/i486-linuxglibc2/include/g++ for a test glibc install or
/usr/i486-linuxlibc5/include/g++ for a primary glibc install.
This can usually be done by appending the $CXXFLAGS variable:
CXXFLAGS = -nostdinc -I/usr/i486-linuxglibc2/include -I/usr/lib/gcc-lib/i486-linuxglibc2/2.7.2.2/include -I/usr/i486-linuxlibc5/include/g++ -b i486-linuxglibc2
The glibc package contains a FAQ with additional information that you should check if you are having problems. An online version is also available at http://www.imaxx.net/~thrytis/glibc/glibc-FAQ.html. Below are some tips for solving problems which are not covered in the FAQ or are covered here in more detail.
Glibc 2 uses a different method than libc 5 in looking up host names.
The glibc name server switch (NSS) code looks for a file
/etc/nsswitch.conf. If host names are not resolving for you
when using a glibc 2 application and your /etc/resolv.conf is
configured correctly, check if you have the /etc/nsswitch.conf
file. If you do not have this file, you can create one containing the
line:
hosts: files dns
/etc/resolv.conf to find the nameservers.
You should look at the section of the libc info pages describing the nsswitch.conf file for more details.
If you think the lib is buggy, please read first the FAQ. It might be that
others had the same problem and there's an easy solution. You should also
check the section "Recommended Tools to Install the GNU C Library" in the
INSTALL file since some bugs are bugs of the tools and not of glibc.
Once you've found a bug, make sure it's really a bug. A good way to do this is to see if the GNU C library behaves the same way some other C library does. If so, probably you are wrong and the libraries are right (but not necessarily). If not, one of the libraries is probably wrong.
Next, go to
http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl,
and look through the bug database. Check here to verify the problem has not
already be reported. You should also look at the file BUGS
(distributed with libc) to check for known bugs.
Once you're sure you've found a new bug, try to narrow it down to the smallest test case that reproduces the problem. In the case of a C library, you really only need to narrow it down to one library function call, if possible. This should not be too difficult.
The final step when you have a simple test case is to report the bug. When
reporting a bug, send your test case, the results you got, the results you
expected, what you think the problem might be (if you've thought of anything),
your system type, the versions of the GNU C library, the GNU CC compiler, and
the GNU Binutils which you are using. Also include the files
config.status and config.make which are created by running
configure; they will be in whatever directory was current when you
ran configure.
All bug reports for the GNU C library should be sent using the
glibcbug shell script which comes with the GNU libc to
bugs@gnu.org (the older address
bugs@gnu.ai.mit.edu
is still working), or submitted through the GNATS web interface at
http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl.
Suggestions and questions should be sent to the mailing list at bugs-glibc@prep.ai.mit.edu. If you don't read the gnewsgroup gnu.bug.glibc, you can subscribe to the list by asking bug-glibc-request@prep.ai.mit.edu.
Please DO NOT send bug report for the GNU C library to <bug-gcc@prep.ai.mit.edu>. That list is for bug reports for GNU CC. GNU CC and the GNU C library are separate entities maintained by separate people.
Included here is a sample specs file for glibc 2 which is used by
gcc for compiling and linking. It should be found in the directory
/usr/lib/gcc-lib/<new system dir>/<gcc version>. If you
are running an x86 system, you probably can copy this section to the file
exactly.
*asm:
%{V} %{v:%{!V:-V}} %{Qy:} %{!Qn:-Qy} %{n} %{T} %{Ym,*} %{Yd,*} %{Wa,*:%*}
*asm_final:
%{pipe:-}
*cpp:
%{fPIC:-D__PIC__ -D__pic__} %{fpic:-D__PIC__ -D__pic__} %{!m386:-D__i486__} %{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}
*cc1:
%{profile:-p}
*cc1plus:
*endfile:
%{!shared:crtend.o%s} %{shared:crtendS.o%s} crtn.o%s
*link:
-m elf_i386 %{shared:-shared} %{!shared: %{!ibcs: %{!static: %{rdynamic:-export-dynamic} %{!dynamic-linker:-dynamic-linker /lib/ld-linux.so.2}}
%{static:-static}}}
*lib:
%{!shared: %{pthread:-lpthread} %{profile:-lc_p} %{!profile: -lc}}
*libgcc:
-lgcc
*startfile:
%{!shared: %{pg:gcrt1.o%s} %{!pg:%{p:gcrt1.o%s} %{!p:%{profile:gcrt1.o%s}
%{!profile:crt1.o%s}}}} crti.o%s %{!shared:crtbegin.o%s} %{shared:crtbeginS.o%s}
*switches_need_spaces:
*signed_char:
%{funsigned-char:-D__CHAR_UNSIGNED__}
*predefines:
-D__ELF__ -Dunix -Di386 -Dlinux -Asystem(unix) -Asystem(posix) -Acpu(i386) -Amachine(i386)
*cross_compile:
0
*multilib:
. ;
This list is intended for discussion among Linux users who have installed glibc2, the new GNU C libraries. Topics might include compatibility issues and questions about the compilation of code in a Linux/glibc setting. To subscribe, send mail to Majordomo@ricardo.ecn.wfu.edu with a body of "subscribe glibc-linux <your email address>.
Archives for this mailing list can be found at http://www.progressive-comp.com/Lists/?l=linux-glibc&r=1&w=2#linux-glibc
Most of this information was stolen from the GNU Libc web page and from Ulrich Drepper's <drepper@gnu.ai.mit.edu> glibc 2 announcement and his comments. Andreas Jaeger <aj@arthur.rhein-neckar.de> provided some of the Reporting bugs section.
The following people have provided information and feedback for this document:
Translations of this document are being done by:
Besides writing this HOWTO, maintaining the glibc 2 for Linux page, and using it on my machine, I have nothing to do with the glibc project. I am far from knowledgeable on this topic, though I try to help with problems mailed to me. I welcome any feedback, corrections, or suggestions you have to offer. Please send them to ejg3@cornell.edu.
Copyright (c) 1997 by Eric Green. This document may be distributed under the terms set forth in the LDP license.