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how to debug

Guest on 2nd May 2022 01:45:42 AM

  1. Debugging util-linux programs
  2. =============================
  3.  
  4. How to deal libtool
  5. -------------------
  6.  
  7. There are considerations to be made when profiling or debugging some programs
  8. found in the util-linux package. Because wrapper scripts are used for the
  9. binaries to make sure all library dependencies are met, you cannot use tools
  10. such as gdb or valgrind directly with them.
  11.  
  12. Let's take for example the mount command:
  13.  
  14.         $> cd /path/to/util-linux
  15.         $> file mount/mount
  16.         mount/mount: Bourne-Again shell script text executable
  17.  
  18. The binary itself is located in the mount/.libs/ directory:
  19.  
  20.         $> file mount/.libs/mount
  21.         mount/.libs/mount: ELF 64-bit LSB executable, x86-64, version 1 \
  22.         (SYSV), dynamically linked (uses shared libs) [...]
  23.  
  24. When this command is run, there's a library dependency error:
  25.  
  26.         $> mount/.libs/mount
  27.         mount/.libs/mount: /lib/libblkid.so.1: version `BLKID_2.20' not found \
  28.         (required by mount/.libs/mount)
  29.  
  30. To overcome this we need set the LD_LIBRARY_PATH variable to read the path of
  31. the shared lib found in the sources, and not system-wide:
  32.  
  33.         $> export LD_LIBRARY_PATH=$PWD/libblkid/src/.libs/:$LD_LIBRARY_PATH
  34.  
  35. Now external debugging tools can be run on the binary.
  36.  
  37. Happy hacking!
  38. Davidlohr Bueso, August
  39.  
  40.  
  41. The libmount & libblkid
  42. -----------------------
  43.  
  44. Both of the libraries can be debugged by setting an environment variable
  45. consisting of a number. The number will be used as a bit mask, so the more 1 the
  46. higher the debugging level. Search for `DEBUG' from files
  47.  
  48.         libblkid/src/blkidP.h
  49.         libmount/src/mountP.h
  50.  
  51. to see what the different bits mean. At the time of writing this the following
  52. enabled full debug.
  53.  
  54.         export LIBBLKID_DEBUG=all
  55.         export LIBMOUNT_DEBUG=all
  56.         export LIBFDISK_DEBUG=all
  57.         export LIBSMARTCOLS_DEBUG=all
  58.  
  59. The libblkid reads by default /etc/blkid.conf which can be overridden by the
  60. environment variable BLKID_CONF. See manual libblkid/libblkid.3 for details
  61. about the configuration file.
  62.  
  63. Block device information is normally kept in a cache file (see blkid man page
  64. for more information about the cache file location) that can be overridden by
  65. the environment variable BLKID_FILE.
  66.  
  67. To libmount uses three paths, which can be overridden by using environment
  68. variables. Notice that these environment variables are ignored for non-root
  69. users.
  70.  
  71.         env variable            if not set defaults to
  72.         LIBMOUNT_FSTAB          /etc/fstab
  73.         LIBMOUNT_MTAB           /etc/mtab
  74.         LIBMOUNT_UTAB           /run/mount/utab or /dev/.mount/utab

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