After upgrade process fails, all programs executing libc functions depending on NSS will fail:

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inaddy@workstation:~/bugs/winbindsegfault/crashes$ ls -ltr 
total 1024 
-rw------- 1 inaddy inaddy 52309 May 21 20:06 winbind.0.crash 
-rw------- 1 inaddy inaddy 52717 May 21 20:06 libwbclient0.0.crash 
-rw------- 1 inaddy inaddy 52094 May 21 20:06 libpam-winbind.0.crash 
-rw-r----- 1 inaddy inaddy 75007 May 21 20:06 _bin_tar.0.crash 
-rw------- 1 inaddy inaddy 516096 May 21 20:06 core 
-rw-r----- 1 inaddy inaddy 73918 May 21 20:06 _bin_ls.1107.crash 
-rw-r----- 1 inaddy inaddy 73430 May 21 20:06 _bin_tar.1107.crash 
-rw-r----- 1 inaddy inaddy 40434 May 21 20:06 _usr_lib_openssh_sftp-server.1107.crash 
-rw-r----- 1 inaddy inaddy 41838 May 21 20:07 _usr_bin_scp.1107.crash 
-rw-r----- 1 inaddy inaddy 56520 May 21 20:07 _bin_ps.1107.crash 

----

(gdb) bt
#0  0x00007ffff68b8b80 in __pthread_initialize_minimal_internal () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007ffff68b7539 in _init () from /lib/x86_64-linux-gnu/libpthread.so.0
#2  0x00007ffff6ad0d48 in ?? () from /lib/x86_64-linux-gnu/libnss_compat.so.2
#3  0x00007ffff7dea0cd in call_init (l=0x6248c0, argc=argc@entry=4, argv=argv@entry=0x7fffffffe428, env=env@entry=0x7fffffffe450) at dl-init.c:64
#4  0x00007ffff7dea215 in call_init (env=0x7fffffffe450, argv=0x7fffffffe428, argc=4, l=<optimized out>) at dl-init.c:36
#5  _dl_init (main_map=main_map@entry=0x624d70, argc=4, argv=0x7fffffffe428, env=0x7fffffffe450) at dl-init.c:93
#6  0x00007ffff7deec40 in dl_open_worker (a=a@entry=0x7fffffffd7d8) at dl-open.c:577
#7  0x00007ffff7de9fc4 in _dl_catch_error (objname=objname@entry=0x7fffffffd7c8, errstring=errstring@entry=0x7fffffffd7d0,
    mallocedp=mallocedp@entry=0x7fffffffd7c0, operate=operate@entry=0x7ffff7dee970 <dl_open_worker>, args=args@entry=0x7fffffffd7d8)
    at dl-error.c:187
#8  0x00007ffff7dee38b in _dl_open (file=0x7fffffffda20 "libnss_compat.so.2", mode=-2147483647, caller_dlopen=<optimized out>, nsid=-2, argc=4,
    argv=0x7fffffffe428, env=0x7fffffffe450) at dl-open.c:661
#9  0x00007ffff771fe92 in do_dlopen (ptr=ptr@entry=0x7fffffffd9f0) at dl-libc.c:87
#10 0x00007ffff7de9fc4 in _dl_catch_error (objname=0x7fffffffd9d0, errstring=0x7fffffffd9e0, mallocedp=0x7fffffffd9c0,
    operate=0x7ffff771fe50 <do_dlopen>, args=0x7fffffffd9f0) at dl-error.c:187
#11 0x00007ffff771ff52 in dlerror_run (args=0x7fffffffd9f0, operate=0x7ffff771fe50 <do_dlopen>) at dl-libc.c:46
#12 __GI___libc_dlopen_mode (name=name@entry=0x7fffffffda20 "libnss_compat.so.2", mode=mode@entry=-2147483647) at dl-libc.c:163
#13 0x00007ffff770747d in nss_load_library (ni=0x623b60, ni=0x623b60) at nsswitch.c:399
#14 __GI___nss_lookup_function (ni=0x623b60, fct_name=fct_name@entry=0x7ffff776810a "getpwuid_r") at nsswitch.c:507
#15 0x00007ffff77076b5 in __GI___nss_lookup (ni=ni@entry=0x7fffffffdae0, fct_name=fct_name@entry=0x7ffff776810a "getpwuid_r",
    fct2_name=fct2_name@entry=0x0, fctp=fctp@entry=0x7fffffffdaf0) at nsswitch.c:239
#16 0x00007ffff7708280 in __GI___nss_passwd_lookup2 (ni=ni@entry=0x7fffffffdae0, fct_name=fct_name@entry=0x7ffff776810a "getpwuid_r",
    fct2_name=fct2_name@entry=0x0, fctp=fctp@entry=0x7fffffffdaf0) at XXX-lookup.c:75
#17 0x00007ffff76aa428 in __getpwuid_r (uid=uid@entry=0, resbuf=resbuf@entry=0x7ffff79ab280 <resbuf.10867>, buffer=0x623410 "", buflen=1024,
    result=result@entry=0x7fffffffdb40) at ../nss/getXXbyYY_r.c:205
#18 0x00007ffff76a9ba6 in getpwuid (uid=0) at ../nss/getXXbyYY.c:116
#19 0x000000000040c9fd in ?? ()
#20 0x000000000040624d in ?? ()
#21 0x0000000000408b19 in ?? ()
#22 0x0000000000403448 in ?? ()
#23 0x00007ffff760bf45 in __libc_start_main (main=0x4028c0, argc=4, argv=0x7fffffffe428, init=<optimized out>, fini=<optimized out>,
    rtld_fini=<optimized out>, stack_end=0x7fffffffe418) at libc-start.c:287
#24 0x00000000004048b9 in ?? ()

----

root@winbindsegfault:~/trusty/samba-4.3.9+dfsg$ ldd  /lib/x86_64-linux-gnu/libnss_winbind.so.2
/lib/x86_64-linux-gnu/libnss_winbind.so.2: /usr/lib/x86_64-linux-gnu/samba/libwinbind-client.so.0: version `SAMBA_4.3.9_UBUNTU' not found (required by /lib/x86_64-linux-gnu/libnss_winbind.so.2)
	linux-vdso.so.1 =>  (0x00007ffc271e8000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fbdf4280000)
	libwinbind-client.so.0 => /usr/lib/x86_64-linux-gnu/samba/libwinbind-client.so.0 (0x00007fbdf4078000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fbdf3cb0000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fbdf46c0000)