使用 python API 访问 Systemd 日志

Question

我使用 Ubuntu 18.04，我想在 python 脚本中阅读我的日记。 作为用户，我可以使用命令阅读日志

journaltctl -f -u foo.service

我想用python读取最后一行：

第一次尝试：

$ python
>>> from systemd import journal
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'systemd'

好的，我当然需要 API：

$ sudo apt install python-systemd
$ python
>>> from systemd import journal
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'journal'

从这里，我无法弄清楚为什么它不起作用。

第三次尝试：

$ sudo python
>>> from systemd import journal
>>>

好的，这似乎是一个权限问题。然后我将当前用户添加到systemd-journal 组：

$ sudo usermod -aG systemd-journal user
<logout/login>
$ groups user
user : user adm cdrom sudo dip plugdev systemd-journal lpadmin sambashare docker

然后

$ python
>>> from systemd import journal
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'journal'

来自documentation：

请注意，为了访问系统日志，非 root 用户必须具有必要的权限，详情请参阅 journalctl(1)。非特权用户只能访问自己的日志。

所以至少我希望能够导入journal 模块并阅读user 日志？

Answer 1

你确定python指的是系统python吗？如果您在虚拟环境或其他 Python 二进制文件中运行，它不会看到使用 apt 安装的包。

我有一个 Ubuntu 18.04 系统：

root@cff463fdd322:/# cat /etc/os-release
NAME="Ubuntu"
VERSION="18.04.3 LTS (Bionic Beaver)"
[...]

如果我安装python-systemd 包：

root@cff463fdd322:/# apt install python-systemd
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  file libexpat1 libmagic-mgc libmagic1 libpython-stdlib libpython2.7-minimal
  libpython2.7-stdlib libreadline7 libsqlite3-0 libssl1.1 mime-support python
  python-minimal python2.7 python2.7-minimal readline-common xz-utils
Suggested packages:
  python-doc python-tk python2.7-doc binutils binfmt-support readline-doc
The following NEW packages will be installed:
  file libexpat1 libmagic-mgc libmagic1 libpython-stdlib libpython2.7-minimal
  libpython2.7-stdlib libreadline7 libsqlite3-0 libssl1.1 mime-support python
  python-minimal python-systemd python2.7 python2.7-minimal readline-common xz-utils
0 upgraded, 18 newly installed, 0 to remove and 0 not upgraded.
Need to get 6440 kB of archives.
After this operation, 29.0 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
[...]

我可以毫无问题地导入systemd.journal 模块：

root@cff463fdd322:/# python
Python 2.7.15+ (default, Oct  7 2019, 17:39:04)
[GCC 7.4.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from systemd import journal
>>>

Answer 2

终于找到解决办法了！

正如@larsks 所指出的，我尝试在虚拟环境中导入包。如文档中所述：

该项目也可以在 pypi 上作为 systemd-python 使用。

但为了能够正确安装，我也需要安装libsystemd-dev 包

$ sudo apt install libsystemd-dev

然后我可以安装 PyPi 包

$ pip install systemd-python

Answer 3

可能就像安装python3-systemd而不是python-systemd一样简单

$ python
Python 3.6.8 (default, Oct  7 2019, 12:59:55) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from systemd import journal
>>> j = journal.Reader()
>>> j.this_boot()
>>> j.log_level(journal.LOG_INFO)
>>> j.add_match(_SYSTEMD_UNIT="systemd-udevd.service")
>>> for entry in j:
...     print(entry['MESSAGE'])
... 
checking bus 1, device 9: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.4/1-4.4.2"
bus: 1, device: 9 was not an MTP device
link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
checking bus 1, device 2: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-1"
bus: 1, device: 2 was not an MTP device
checking bus 1, device 3: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
bus: 1, device: 3 was not an MTP device