Introduction to the use of Ldconfig in Linux

Introduction to the use of Ldconfig in Linux

Ldconfig is a dynamic link Library management command designed to allow dynamic link libraries to be shared by the system.

Main uses of Ldconfig:

The default searches for/lilb and/usr/lib, as well as the library files in the directory listed in the configuration file/etc/ld.so.conf.

Search for a shareable dynamic-link library, with the format of the library file: lib***.so.**, which creates the connection and cache files required for the dynamic loader (ld.so).

The cache file defaults to/etc/ld.so.cache, which holds the list of dynamically linked library names that have been ordered.

Ldconfig usually runs at system startup, and when a user installs a new dynamic-link library, they need to run the command manually.

Ldconfig Command parameter Description:

1,-V, or--verbose: With this option, Ldconfig will display the directory being scanned and the dynamic-link library It was searching for, as well as the name of the connection it created.

2,-N: With this option, Ldconfig scans only the directories specified by the command line, does not scan the default directory (/lib,/usr/lib), and does not scan directories listed in the configuration file/etc/ld.so.conf.

3,-N: This option indicates that Ldconfig does not rebuild the cache file (/etc/ld.so.cache). If the-X option is not used, the connection to the file is updated Ldconfig as usual.

4.-X: This option indicates that Ldconfig does not update the file's connection. If the-n option is not used, the cache file is updated normally.

5,-F CONF: This option specifies that the profile for the dynamic link library is CONF and the system defaults to/etc/ld.so.conf.

6,-C cache: This option specifies that the generated cache file is cached, and the system defaults to/etc/ld.so.cache, which holds a list of queued, shareable, dynamic-link libraries.

7.-R root: This option changes the root of the application to be root (called the chroot function). When this option is selected, the system default configuration file/etc/ld.so.conf, which corresponds to root/etc/ld.so.conf.-r/usr/ ZZZ, when you open the configuration file/etc/ld.so.conf, the/usr/zzz/etc/ld.so.conf file is actually opened. With this option, you can greatly increase the flexibility of dynamic link library management.

8,-L: Typically, Ldconfig will automatically establish a connection to a dynamic-link library when it searches for a dynamic-link library. When you select this option, you will enter expert mode and you need to manually set up the connection. This is not required for general users.

9,-P or--print-cache: This option instructs Ldconfig to print out the names of all shared libraries that are saved by the current cache file.

10,-C format or--format=format: This option specifies the format in which the cache file is used, in total three types: LD (old format), new (newer format), and Compat (the default format).

11,-V: This option prints out the version information for Ldconfig and then exits.

12,-or--help or--usage: These three options have the same effect, which is to let Ldconfig print out its Help information and then exit.

Ldconfig areas to note:

1, to/lib and/usr/lib inside add things, is not modified/etc/ld.so.conf file, but after adding the need to call the next ldconfig, or the added library will not be found.

2, if the added library is not in/lib and/usr/lib inside, it is necessary to modify the/etc/ld.so.conf file, the file is appended to the path of the library, and then need to recall the next Ldconfig command. For example, when you install MySQL, its library file/usr/local/mysql/lib, you need to append to the/etc/ld.so.conf file. The command is as follows:

# echo "/usr/local/mysql/lib" >>/etc/ld.so.conf

# Ldconfig-v | grep MySQL

3, if the addition of the LIBRARY is not/lib or/usr/lib, but do not have permission to write/etc/ld.so.conf file, then you need to write a global variable Ld_library_path in the export, you can.

Introduction to the use of Ldconfig in Linux