我正在使用带有 systemd 的 Ubuntu 18.04 Server。最近，我们部门开发的一个程序在一天内崩溃了两次，并出现以下错误：
Jun 07 06:33:07 xxx systemd[1]: xxx.service: Main process exited, code=killed, status=11/SEGV
Jun 07 06:33:07 xxx systemd[1]: xxx.service: Failed with result 'signal'.
我认为下一步是获取回溯或核心转储，但我不确定如何在使用 systemd 的 Ubuntu Server 上执行此操作。
我不确定是否应该继续使用systemd-coredump、coredumpctl或其他实用程序。
另外，我不确定要发出什么命令。对于上述实用程序，有大量关于各种功能等的文档，但我找不到类似这样的简洁示例：
sudo apt-get install xyz
(run x, y, z commands to get core dump)
有人能提供一个简明的例子或一个能很好地解释这一点的教程网站吗？我不需要也不想使用各种复杂的功能，我只是想获得一个基本的核心转储。
答案1
以一个相对简单的服务——chrony NTP 守护进程为例。
使用 dbgsym 包安装调试符号。 不幸的是，默认情况下，ddebs repo 不在源文件中。此外，没有很好的脚本来查找包，因此首先在包名称后附加 -dbgsym。
sudo apt install chrony-dbgsym
你可能需要考虑如何处理现代 Linux 服务器上的核心转储 在他们的情况下，他们正在考虑恢复仅使用核心转储文件。就我个人而言，我在服务器上没有从 apport 中获得任何有用的东西，但发现 coredumpctl 很有用。因此，Ubuntu 18.04 上的 systemd 方法：
sudo systemctl stop apport
sudo systemctl mask --now apport
sudo apt install systemd-coredump
# Verify this changed the core pattern to a pipe to systemd-coredump
sysctl kernel.core_pattern
# Reproduce the crash.
sudo killall -s SIGSEGV chronyd
# List collected dumps.
coredumpctl
# Invoke debugger on the latest one.
sudo coredumpctl gdb
# systemd >= 239 the gdb verb was renamed debug. Also, select core by PID.
sudo coredumpctl debug 5809
# In GDB, the basic thing to get is a stack trace. Ask the developer what else they want.
(gdb) thread apply all bt
启动调试器会话可能如下所示：
John@coredump:~$ coredumpctl
TIME PID UID GID SIG COREFILE EXE
Sat 2019-06-08 12:55:16 UTC 5809 111 115 11 error /usr/sbin/chronyd
John@coredump:~$ sudo coredumpctl gdb
PID: 5809 (chronyd)
UID: 111 (_chrony)
GID: 115 (_chrony)
Signal: 11 (SEGV)
Timestamp: Sat 2019-06-08 12:55:16 UTC (1h 19min ago)
Command Line: /usr/sbin/chronyd
Executable: /usr/sbin/chronyd
Control Group: /system.slice/chrony.service
Unit: chrony.service
Slice: system.slice
Boot ID: c9a0a69a73d245c1ae5dfe7d491ead0a
Machine ID: d2934a6e67f81ae0097be31003da0b31
Hostname: coredump
Storage: /var/lib/systemd/coredump/core.chronyd.111.c9a0a69a73d245c1ae5dfe7d491ead0a.5809.1559998516000000.lz4
Message: Process 5809 (chronyd) of user 111 dumped core.
Stack trace of thread 5809:
#0 0x00007eff1ce1403f __GI___select (libc.so.6)
#1 0x00005597867eb3be n/a (chronyd)
#2 0x00005597867e1071 n/a (chronyd)
#3 0x00007eff1cd1eb97 __libc_start_main (libc.so.6)
#4 0x00005597867e127a n/a (chronyd)
GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/sbin/chronyd...Reading symbols from /usr/lib/debug/.build-id/89/dcd398c87777f4c869bfd0831215eeb8b6c7fe.debug...done.
done.
[New LWP 5809]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/usr/sbin/chronyd'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007eff1ce1403f in __GI___select (nfds=4, readfds=readfds@entry=0x7ffc0fd73c80,
writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=timeout@entry=0x7ffc0fd73be0)
at ../sysdeps/unix/sysv/linux/select.c:41
41 ../sysdeps/unix/sysv/linux/select.c: No such file or directory.
(gdb) thread apply all bt
Thread 1 (Thread 0x7eff1df14740 (LWP 5809)):
#0 0x00007eff1ce1403f in __GI___select (nfds=4, readfds=readfds@entry=0x7ffc0fd73c80,
writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=timeout@entry=0x7ffc0fd73be0)
at ../sysdeps/unix/sysv/linux/select.c:41
#1 0x00005597867eb3be in SCH_MainLoop () at sched.c:747
#2 0x00005597867e1071 in main (argc=<optimized out>, argv=0x7ffc0fd73fb8) at main.c:605
在这个虚构的例子中，当我粗鲁地向等待 I/O 的任务发送信号时，在 select() 中捕获了它。
更复杂的软件可能缺少其他符号，安装这些符号以及源代码并继续调试。