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crle(1)                          User Commands                         crle(1)



NAME
       crle - configure runtime linking environment

SYNOPSIS
       crle  [-64]  [-a name] [-A name] [-c conf] [-e env] [-E env] [-f flags]
       [-i name] [-I name] [-g name] [-G name] [-l dir] [-o dir] [-s dir]  [-t
       [ ELF | AOUT] ] [-u] [-v]

DESCRIPTION
       The  crle  utility  provides  for the creation and display of a runtime
       linking configuration file. The configuration file is read  and  inter-
       preted  by  the  runtime  linker,  ld.so.1(1), during process start-up.
       Without any arguments, or with just the -c option, crle  displays  con-
       figuration  information.  This  information  includes the contents of a
       configuration file, any system defaults and the  command-line  required
       to  regenerate  the  configuration  file.   When  used  with  any other
       options, a new configuration file is created or updated.

       For 32-bit objects, the default configuration file  is  /var/ld/ld.con-
       fig.   For   64-bit   objects,   the   default  configuration  file  is
       /var/ld/64/ld.config.

       When creating a new configuration file, first create the file in a tem-
       porary  location. The environment variable LD_CONFIG can then be set to
       this new configuration file. This setting causes the new  configuration
       to  be used by the runtime linker instead of any default. After verifi-
       cation, the new configuration file can be moved to the default location
       if  desired.  At  any time, the environment variable LD_NOCONFIG can be
       set to any value to instruct the runtime linker to ignore any  configu-
       ration files. This setting can prove useful during experimentation.

       A configuration file can contain the following information.

       Default Search Paths

           The  runtime  linker uses a prescribed search path for locating the
           dynamic dependencies of an object. This search path starts with the
           components  of any LD_LIBRARY_PATH definition, followed by the com-
           ponents of an object's runpath. Finally, any default  search  paths
           specific  to the object's type are used. This last component of the
           search path can be expressed within the configuration  file.  Typi-
           cally,  use  of  this  facility should be augmented with any system
           defaults. See the -l option.



       Trusted Directories

           When processing a secure application, the runtime linker  restricts
           the  use  of LD_LIBRARY_PATH and the directories from which preload
           and audit libraries can be used. This processing is  restricted  to
           known  trusted  directories.   Trusted directories can be expressed
           within the configuration file.  Typically,  use  of  this  facility
           should be augmented with any system defaults. See the -s option.



       Directory Cache

           The  location  of  shared objects within defined directories can be
           maintained as a cache within the configuration file. This directory
           cache  can  reduce the overhead of searching for application depen-
           dencies.



       Alternative Objects

           In conjunction with the directory cache, shared  objects  can  have
           alternative  objects  specified for use at runtime. These alternate
           objects, can be supplied by the user. Alternative objects can  also
           be  created by crle as copies of shared objects fixed to known mem-
           ory locations. These fixed alternative  objects  can  require  less
           processing  at  runtime  than their original shared object counter-
           part.



       Environment Variables

           Any environment variable interpreted by the runtime linker  can  be
           specified within the configuration file.



       Defining alternative default search paths, or additional trusted direc-
       tories can be useful for administrators who wish to install third party
       software  in  a central location, or otherwise alter the search path of
       applications that might not have been coded with suitable runpaths.

       The declaration of alternative objects, provides a means  of  replacing
       dependencies   other   than  by  using  symbolic  links,  or  requiring
       LD_LIBRARY_PATH settings.

       The declaration of environment variables that are  interpreted  by  the
       runtime  linker,  provides a means of centralizing their definition for
       all applications.

       The directory cache, and crle generated alternate objects, can  provide
       a  means  of  reducing  the  runtime start-up overhead of applications.
       Alternative objects can be useful for applications  that  require  many
       dependencies,  or  whose dependencies are expensive to relocate. Shared
       objects that contain position-dependent code  are  often  expensive  to
       relocate.

       When  alternate objects that are generated by crle are specified within
       a configuration file, ld.so.1(1) performs some minimal consistency ver-
       ification. The alternative objects are verified against their originat-
       ing objects. This verification is intended to avert application failure
       should  an  applications  configuration  information become out-of-sync
       with the underlying system components. When this situation  arises  the
       flexibility offered by dynamic linking system components can be compro-
       mised. This type of application failure can be very difficult to  diag-
       nose.  No verification of directory cache information is performed. Any
       changes to the directory structure are not seen by a process until  the
       cache is rebuilt.

       System shared objects are often well tuned, and can slow little benefit
       from being cached. The directory cache and alternative object  features
       are typically applicable to user applications and shared objects.

       crle  creates alternate objects for the shared objects that are discov-
       ered when using the -I and -G options,  by  calls  to  dldump(3C).  The
       alternate object is created in the directory specified by the preceding
       -o option, or defaults to the directory in which the configuration file
       is  created. The flags used for the dldump() are specified using the -f
       option, or default to RTLD_REL_RELATIVE.

OPTIONS
       The following options are supported.

       -64

           Specify to process 64-bit objects, the default is 32-bit.



       -a name

           Create an alternative pathname for name. The  alternative  pathname
           is added to the configuration file.

           The  actual alternative file must be supplied by the user. Multiple
           occurrences of this option are permitted. If name is  a  directory,
           each  shared  object within the directory is added to the cache. If
           name does not exist, then name is marked in the cache as a nonexis-
           tent file.

           Typically, this option is used with the -o option.



       -A name

           Create  an optional alternative pathname for name. This alternative
           pathname is added to the configuration file.

           This option mimics the -a option, except that if the alternative is
           unavailable  at  runtime,  the  original  object name is used. This
           model mimics the use of  auxiliary  filters.  See  the  Linker  and
           Libraries Guide.

           Typically, this option is used with the -o option.



       -c conf

           Specify  to use the configuration file name conf. If this option is
           not supplied, the default configuration file is used.



       -e env

           Specify a replaceable environment variable, env.  Only  environment
           variables that are applicable to the runtime linker are meaningful.
           Multiple occurrences of this option are permitted. This  option  is
           similar  to the -E option. However, the options differs in how con-
           figuration file definitions, and process environment definitions of
           the same name are resolved at runtime.

           A  definition established in a configuration file can be overridden
           by a process environment definition, or be suppressed  by  a  null-
           value process environment definition.

           In  other  words,  these  configuration  file  definitions  can  be
           replaced, or removed by the process environment at runtime.



       -E env

           Specify a permanent environment  variable,  env.  Only  environment
           variables that are applicable to the runtime linker are meaningful.
           Multiple occurrences of this option are permitted. This  option  is
           similar  to  the -e option. However, the option differs in how con-
           figuration file definitions, and process environment definitions of
           the same name are resolved at runtime.

           Environment variable definitions that are meaningful to the runtime
           linker fall into one of two categories.  Singular  definitions  are
           definitions  such as LD_NOLAZYLOAD=1 and LD_DEBUG_OUTPUT=file. List
           definitions, which can take one or  more  values,  are  definitions
           such as LD_LIBRARY_PATH=path, and LD_DEBUG=files,details.

           A  singular  definition that is established in a configuration file
           takes precedence over a process environment definition. A list def-
           inition  that is established in a configuration file is appended to
           a process environment definition. Any  definition  that  is  estab-
           lished  in  a  configuration  file can not be suppressed by a null-
           value process environment definition.

           In other words, these configuration file  definitions  can  not  be
           replaced, or removed by the process environment at runtime.



       -f flags

           Provide the symbolic flags argument to the dldump(3C) calls used to
           generate alternate objects. Any of  the  RTLD_REL  flags  that  are
           defined  in /usr/include/dlfcn.h can be used. Multiple flags can be
           or'ed together using the "|" character. In this  case,  the  string
           should  be quoted to avoid expansion by the shell. If no flags val-
           ues are provided the default flag is RTLD_REL_RELATIVE.



       -i name

           Add an individual name to the configuration cache. Multiple  occur-
           rences of this option are permitted. name can be a shared object or
           a directory. If name is a directory, each shared object within  the
           directory  is  added to the cache. If name does not exist, the name
           is marked in the cache as a nonexistent directory.



       -I name

           Mimic the -i, and in addition any shared object that  is  processed
           has  an  alternative  created using dldump(3C). If the -f flag con-
           tains RTLD_REL_EXEC, then name can be  a  dynamic  executable,  for
           which an alternative is created. Only one dynamic executable can be
           specified in this manner, as the cache that is created is  specific
           to this application.



       -g name

           Add  the  group  name  to  the  configuration cache. Each object is
           expanded to determine its  dependencies.  Multiple  occurrences  of
           this option are permitted. name can be a dynamic executable, shared
           object or a directory. If name  is  a  shared  object,  the  shared
           object  and  its  dependencies are added to the cache. If name is a
           directory, each shared object within the directory, and its  depen-
           dencies, are added to the cache.



       -G name

           Mimic the -g option, and in addition any shared object that is pro-
           cessed has an alternative created using dldump(3C). If  name  is  a
           dynamic executable, and the -f flag contains RTLD_REL_EXEC, then an
           alternative for the dynamic executable is also  created.  Only  one
           dynamic  executable  can  be  specified in this manner as the cache
           that is created is specific to this application.



       -l dir

           Specify a new default search directory dir for ELF or AOUT objects.
           Multiple  occurrences  of  this  option  are permitted. The type of
           object that is applicable to the search, is specified by  the  pre-
           ceding -t option, or defaults to ELF.

           The  default  search paths for 32-bit ELF objects are /lib followed
           by /usr/lib. For 64-bit ELF objects, the default search  paths  are
           /lib/64 followed by /usr/lib/64.

           The  default  search paths for AOUT objects are /usr/4lib, followed
           by /usr/lib and finally /usr/local/lib.

           Use of this option replaces the default search path.  Therefore,  a
           -l  option  is  normally  required  to  specify the original system
           default in relation to any new paths that are being  applied.  How-
           ever,  if the -u option is in effect, and a configuration file does
           not exist, the system defaults are added to the  new  configuration
           file.  These defaults are added before the new paths specified with
           the -l option.



       -o dir

           When used with either the -a or -A options, specifies the directory
           dir  in which any alternate objects exist. When alternative objects
           are created by crle, this option specified  where  the  alternative
           are  created.  Without  this option, alternate objects exist in the
           directory in which the  configuration  file  is  created.  Multiple
           occurrences  of  this option are permitted, the directory dir being
           used to locate alternatives for any following command-line options.
           Alternative  objects are not permitted to override their associated
           originals.

           Typically, this option is used with the -a or -A options.



       -s dir

           Specify a new trusted directory dir for secure ELF or AOUT objects.
           See SECURITY in ld.so.1(1) for a definition of secure objects.

           Multiple  occurrences  of  this  option  are permitted. The type of
           object that is applicable to the search is specified by the preced-
           ing -t option, or defaults to ELF.

           The  default  trusted directories for secure 32-bit ELF objects are
           /lib/secure followed by  /usr/lib/secure.  For  64-bit  secure  ELF
           objects,  the  default  trusted directories are /lib/secure/64 fol-
           lowed by /usr/lib/secure/64.

           The  default  trusted  directories  for  secure  AOUT  objects  are
           /usr/4lib,  followed  by  /usr/lib,  followed  by  /usr/ucblib, and
           finally /usr/local/lib.

           Use of this option replaces the default trusted directories. There-
           fore, a -s option is normally required to specify the original sys-
           tem default in relation to  any  new  directories  that  are  being
           applied.  However,  if the -u option is in effect, and a configura-
           tion file does not exist, the system defaults are added to the  new
           configuration  file. These defaults are added before the new direc-
           tories specified with the -l option.



       -t ELF | AOUT

           Toggle the object type that is applicable to any -l or  -s  options
           that follow. The default object type is ELF.



       -u

           Request  that  a  configuration  file be updated, possibly with the
           addition of new information. Without other  options,  any  existing
           configuration  file is inspected and its contents recomputed. Addi-
           tional arguments allow information to be appended to the recomputed
           contents. See NOTES.

           If  a  configuration file does not exist, the configuration file is
           created as directed by the other arguments. In the case of  the  -l
           and  -s  options, any system defaults are first applied to the con-
           figuration  file  before  the  directories  specified  with   these
           options.



       -v

           Specify  verbose  mode. When creating a configuration file, a trace
           of the files that are being processed is written  to  the  standard
           out.  When  printing  the  contents  of  a configuration file, more
           extensive directory and file information is provided.



       By default, the runtime linker attempts to read the configuration  file
       /var/ld/ld.config    for    each    32-bit   application   processesed.
       /var/ld/64/ld.config is read for each 64-bit application. When process-
       ing  an  alternative  application,  the  runtime  linker  uses  a $ORI-
       GIN/ld.config.app-name configuration file if present. See NOTES. Appli-
       cations  can reference an alternative configuration file by setting the
       LD_CONFIG environment variable. See ld.so.1(1). An alternative configu-
       ration  file  can also be specified by recording the configuration file
       name in the application at the time the application is built.  See  the
       -c option of ld(1).

EXAMPLES
       Example  1:  Updating  and Displaying a New Default Search Path for ELF
       Objects

       The following example updates and displays a new  default  search  path
       for ELF objects:

       example% crle -u -l /local/lib
       example% crle

       Configuration file [version 4]: /var/ld/ld.config
         Default Library Path (ELF):  /lib:/usr/lib:/local/lib
         Trusted Directories (ELF):   /lib/secure:/usr/lib/secure (system default)

       Command line:
         crle -l /lib:/usr/lib:/local/lib

       example% crle -u -l /usr/local/lib
       example% crle

       Configuration file [version 4]: /var/ld/ld.config
         Default Library Path (ELF):  /lib:/usr/lib:/local/lib:/usr/local/lib
         Trusted Directories (ELF):   /lib/secure:/usr/lib/secure (system default)

       Command line:
         crle -l /lib:/usr/lib:/local/lib:/usr/local/lib


       In  this  example,  the  default  configuration  file initially did not
       exist. Therefore, the new search path /local/lib  is  appended  to  the
       system  default. The next update appends the search path /usr/local/lib
       to those paths already established in the configuration file.

       Example 2: Creating and Displaying a New Default Search  Path  and  New
       Trusted Directory for ELF Objects

       The  following  example  creates and displays a new default search path
       and new trusted directory for ELF objects:

       example% crle -l /local/lib -l /lib -l /usr/lib -s /local/lib
       example% crle

       Configuration file [version 4]: /var/ld/ld.config
         Default Library Path (ELF):  /local/lib:/lib:/usr/lib
         Trusted Directories (ELF):   /local/lib

       Command line:
         crle -l /local/lib:/lib:/usr/lib -s /local/lib


       With this configuration, third party applications could be installed in
       /local/bin and their associated dependencies in /local/lib. The default
       search path allows the applications to locate their dependencies  with-
       out  the  need  to set LD_LIBRARY_PATH. The default trusted directories
       have also been replaced with this example.

       Example 3: Creating a Directory Cache for ELF Objects

       The following example creates a directory cache for ELF objects:

       example% crle -i /usr/dt/lib -i /usr/openwin/lib -i /lib -i /usr/lib \
               -c config
       example% ldd -s ./main
       ....
          find object=libc.so.1; required by ./main
           search path=/usr/dt/lib:/usr/openwin/lib  (RPATH ./main)
           trying path=/usr/dt/lib/libc.so.1
           trying path=/usr/openwin/lib/libc.so.1
           search path=/lib  (default)
           trying path=/lib/libc.so.1
               libc.so.1 =>     /lib/libc.so.1

       example% LD_CONFIG=config ldd -s ./main
       ....
          find object=libc.so.1; required by ./main
           search path=/usr/dt/lib:/usr/openwin/lib  (RPATH ./main)
           search path=/lib  (default)
           trying path=/lib/libc.so.1
               libc.so.1 =>     /lib/libc.so.1

       With this configuration, the cache reflects  that  the  system  library
       libc.so.1  does  not exist in the directories /usr/dt/lib or /usr/open-
       win/lib. Therefore, the search  for  this  system  file  ignores  these
       directories even though the application's runpath indicates these paths
       should be searched.

       Example 4: Creating an Alternative Object Cache for an ELF Executable

       The following example creates an alternative object cache  for  an  ELF
       executable:

       example% crle -c /local/$HOST/.xterm/ld.config.xterm \
               -f RTLD_REL_ALL  -G /usr/openwin/bin/xterm
       example% ln  -s /local/$HOST/.xterm/xterm  /local/$HOST/xterm
       example% ldd /usr/local/$HOST/xterm
           libXaw.so.5 =>  /local/$HOST/.xterm/libWaw.so.5  (alternate)
           libXmu.so.4 =>  /local/$HOST/.xterm/libXmu.so.4  (alternate)
           ....
           libc.so.1 =>    /local/$HOST/.xterm/libc.so.1  (alternate)
           ....

       With  this configuration, a new xterm and its dependencies are created.
       These new objects are fully relocated to  each  other,  and  result  in
       faster  start-up  than  the  originating objects. The execution of this
       application uses its own specific configuration  file.  This  model  is
       generally  more flexible than using the environment variable LD_CONFIG,
       as the configuration file can not be erroneously used by other applica-
       tions such as ldd(1) or truss(1).

       Example  5:  Creating  an  Alternative  Object  Cache to Replace an ELF
       Shared Object

       The following example creates an alternative object cache to replace an
       ELF shared object:

       example% ldd /usr/bin/vi
           libcurses.so.1 =>  /lib/libcurses.so.1
           ....

       example% crle -a /lib/libcurses.so.1 -o /usr/ucblib
       example% crle

       Configuration file [version 4]: /var/ld/ld.config
         Default Library Path (ELF):  /lib:/usr/lib  (system default)
         Trusted Directories (ELF):   /lib/secure:/usr/lib/secure (system default)

       Directory: /lib
         libcurses.so.1  (alternate: /usr/ucblib/libcurses.so.1)
       ....

       example% ldd /usr/bin/vi
           libcurses.so.1 => /usr/ucblib/libcurses.so.1 (alternate)
           ....

       With  this configuration, any dependency that would normally resolve to
       /usr/lib/libcurses.so.1 instead resolves to /usr/ucblib/libcurses.so.1.

       Example 6: Setting Replaceable and Permanent Environment Variables

       The following example sets replaceable and permanent environment  vari-
       ables:

       example% crle -e LD_LIBRARY_PATH=/local/lib \
               -E LD_PRELOAD=preload.so.1
       example% crle
       .....
       Environment Variables:
         LD_LIBRARY_PATH=/local/lib  (replaceable)
         LD_PRELOAD=preload.so.1  (permanent)

       .....
       example% LD_DEBUG=files LD_PRELOAD=preload.so.2 ./main
       .....
       18764: file=preload.so.2;  preloaded
       18764: file=/local/lib/preload.so.2  [ ELF ]; generating link map
       .....
       18764: file=preload.so.1;  preloaded
       18764: file=/local/lib/preload.so.1  [ ELF ]; generating link map
       .....

       With this configuration file, a replaceable search path has been speci-
       fied together with a permanent preload object which becomes appended to
       the process environment definition.

EXIT STATUS
       The  creation  or  display of a configuration file results in a 0 being
       returned. Otherwise, any error condition is accompanied with a diagnos-
       tic message and a non-zero value being returned.

NOTES
       The  ability  to  tag an alternative application to use an application-
       specific configuration file, is possible if  the  original  application
       contains  one  of the .dynamic tags DT_FLAGS_1 or DT_FEATURE_1. Without
       these entries, a configuration file must be specified using the LD_CON-
       FIG  environment  variable.  Care  should be exercised with this latter
       method as this environment variable is visible to any  forked  applica-
       tions.

       The use of the -u option requires at least version 2 of crle. This ver-
       sion level is evident from displaying the contents of  a  configuration
       file:

       example% crle

       Configuration file [2]: /var/ld/ld.config
         ......


       With  a  version  2 configuration file, crle is capable of constructing
       the command-line arguments required  to  regenerate  the  configuration
       file. This command-line construction, provides full update capabilities
       using the -u option. Although a version 1 configuration file update  is
       possible,  the  configuration  file  contents might be insufficient for
       crle to compute the entire update requirements.

FILES
       /var/ld/ld.config

           Default configuration file for 32-bit applications.



       /var/ld/64/ld.config

           Default configuration file for 64-bit applications.



       /var/tmp

           Default location for temporary configuration file. See tempnam(3C).



       /usr/lib/lddstub

           Stub application that is employed to dldump(3C) 32-bit objects.



       /usr/lib/64/lddstub

           Stub application that is employed to dldump(3C) 64-bit objects.



       /usr/lib/libcrle.so.1

           Audit library that is employed to dldump(3C) 32-bit objects.



       /usr/lib/64/libcrle.so.1

           Audit library that is employed to dldump(3C) 64-bit objects.



ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).  ATTRIBUTE TYPEATTRIBUTE VALUE AvailabilitySUNWtoo


SEE ALSO
       ld(1), ld.so.1(1), dldump(3C), tempnam(3C), attributes(5)



SunOS 5.10                        13 May 2004                          crle(1)