我能够通过编辑 unit.service 文件为 php5-fpm 服务设置 umask正如建议的此处和此处.Debian 8 的完整且有效的解决方案是这样的:

I was able to set the umask for php5-fpm service by editing it's unit.service file as suggested here and here. The complete and working solution for Debian 8 is this:

1. 手动编辑 /etc/systemd/system/multi-user.target.wants/php5-fpm.service 文件并在 中添加 UMask=0002 行[服务] 部分.
2. 运行命令systemctl daemon-reload
3. 运行命令systemctl restart php5-fpm.service

1. Manually edit /etc/systemd/system/multi-user.target.wants/php5-fpm.service file and add UMask=0002 line inside [Service] section.
2. Run command systemctl daemon-reload
3. Run command systemctl restart php5-fpm.service

现在服务文件如下所示:

Now the service file looks like this:

[Unit]
Description = The PHP FastCGI Process Manager
After = network.target

[Service]
Type = notify
PIDFile = /var/run/php5-fpm.pid
ExecStartPre = /usr/lib/php5/php5-fpm-checkconf
ExecStart = /usr/sbin/php5-fpm --nodaemonize --fpm-config /etc/php5/fpm/php-fpm.conf
ExecReload = /bin/kill -USR2 $MAINPID
; Added to set umask for files created by PHP
UMask = 0002

[Install]
WantedBy = multi-user.target

注意:

1. 您不能使用 systemctl edit php5-fpm.service 命令，因为 edit 选项是在 systemctl 版本 218 中引入的，但 Debian 8 附带版本 215.
2. 按照对此答案的评论中的建议添加*.conf文件不适用于我，但也许我搞砸了一些东西(欢迎对此发表评论，因为我不喜欢编辑单元文件).

1. You can not use systemctl edit php5-fpm.service command as edit option was introduced in systemctl version 218 but Debian 8 ships with version 215.
2. Adding *.conf file as suggested in comments for this answer did not work for me, but maybe I messed up something (comments are welcome for this as editing unit file is not something that I feel comfortable with).