命令LD_DEBUG

LD_DEBUG 是 glibc 中的 loader 设置的一个环境变量,可以方便的看到 loader 的加载过程。glibc是gnu 发布的libc ,即c运行库 。glibc是linux系统 中最底层的api ,几乎其它任何运行库都会依赖于glibc。

# LD_DEBUG=help ls
 Valid options for the LD_DEBUG environment variable are:

  libs        display library search paths
  reloc       display relocation processing
  files       display progress for input file
  symbols     display symbol table processing
  bindings    display information about symbol binding
  versions    display version dependencies
  all         all previous options combined
  statistics  display relocation statistics
  unused      determined unused DSOs
  help        display this help message and exit

To direct the debugging output into a file instead of standard output
a filename can be specified using the LD_DEBUG_OUTPUT environment variable.

 

以memcached安装过程中遇到的问题为例:

命令: /usr/local/bin/memcached -p 11211 -m 64m -vv
错误:/usr/local/bin/memcached: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory

使用LD_DEBUG显示库寻找信息

LD_DEBUG=libs /usr/local/bin/memcached -vv
     15759:    find library=libevent-2.0.so.5 [0]; searching
     15759:     search cache=/etc/ld.so.cache
     15759:     search path=/lib64/tls/x86_64:/lib64/tls:/lib64/x86_64:/lib64:/usr/lib64/tls/x86_64:/usr/lib64/tls:/usr/lib64/x86_64:/usr/lib64           (system search path)
     15759:      trying file=/lib64/tls/x86_64/libevent-2.0.so.5
     15759:      trying file=/lib64/tls/libevent-2.0.so.5
     15759:      trying file=/lib64/x86_64/libevent-2.0.so.5
     15759:      trying file=/lib64/libevent-2.0.so.5
     15759:      trying file=/usr/lib64/tls/x86_64/libevent-2.0.so.5
     15759:      trying file=/usr/lib64/tls/libevent-2.0.so.5
     15759:      trying file=/usr/lib64/x86_64/libevent-2.0.so.5
     15759:      trying file=/usr/lib64/libevent-2.0.so.5

最后一行可以看出,memcached去/usr/lib64目录下寻找libevent-2.0.so.5,先定位libevent-2.0.so.5实际目录

命令:whereis libevent-2.0.so.5

结果:libevent-2.0.so: /usr/lib/libevent-2.0.so.5

这时候需要将做一个软连接

命令:ln -s /usr/lib/libevent-2.0.so.5 /usr/lib64/libevent-2.0.so.5

 

如果要删除软连接

命令: rm -rf filename

 

到此问题解决

 

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