新安装lighttpd出现gw_backend.c错误，PHP无法正常运行求助

问题现象 #

• 服务器可正常处理HTML文件，但PHP程序无法运行
• 日志反复输出两条报错：

  (gw_backend.c.324) child exited: 0 unix:/var/run/lighttpd/php.socket-0
  (gw_backend.c.468) unlink /var/run/lighttpd/php.socket-0 after connect failed: Connection refused
  

• 使用命令sudo lighttpd -D -f /etc/lighttpd/lighttpd.conf启动服务无报错

配置信息 #

lighttpd.conf 文件内容 #

server.modules = (
    "mod_indexfile",
    "mod_access",
    "mod_alias",
    "mod_redirect",
        "mod_compress",
    "mod_dirlisting",
    "mod_staticfile",
)

server.document-root        = "/var/www/html"
server.upload-dirs          = ( "/var/cache/lighttpd/uploads" )
server.errorlog             = "/var/log/lighttpd/error.log"
server.pid-file             = "/run/lighttpd/lighttpd.pid"
server.username             = "www-data"
server.groupname            = "www-data"
server.port                 = 8078

# strict parsing and normalization of URL for consistency and security
# https://redmine.lighttpd.net/projects/lighttpd/wiki/Server_http-parseoptsDetails
# (might need to explicitly set "url-path-2f-decode" = "disable"
#  if a specific application is encoding URLs inside url-path)
server.http-parseopts = (
  "header-strict"           => "enable",# default
  "host-strict"             => "enable",# default
  "host-normalize"          => "enable",# default
  "url-normalize-unreserved"=> "enable",# recommended highly
  "url-normalize-required"  => "enable",# recommended
  "url-ctrls-reject"        => "enable",# recommended
  "url-path-2f-decode"      => "enable",# recommended highly (unless breaks app)
 #"url-path-2f-reject"      => "enable",
  "url-path-dotseg-remove"  => "enable",# recommended highly (unless breaks app)
 #"url-path-dotseg-reject"  => "enable",
 #"url-query-20-plus"       => "enable",# consistency in query string
)

index-file.names            = ( "index.php", "index.html" )
url.access-deny             = ( "~", ".inc" )
static-file.exclude-extensions = ( ".php", ".pl", ".fcgi" )

compress.cache-dir          = "/var/cache/lighttpd/compress/"
compress.filetype           = ( "application/javascript", "text/css", "text/html", "text/plain" )

# default listening port for IPv6 falls back to the IPv4 port
## Use ipv6 if available
#include_shell "/usr/share/lighttpd/use-ipv6.pl " + server.port
include_shell "/usr/share/lighttpd/create-mime.conf.pl"
include "/etc/lighttpd/conf-enabled/*.conf"

#server.compat-module-load   = "disable"
fastcgi.server = ( ".php" => ((
                     "bin-path" => "/bin/php7.4",
                     "socket" => "/var/run/lighttpd/php.socket",
                     "max-procs" => 1,
                     "bin-environment" => (
                       "PHP_FCGI_CHILDREN" => "16",
                       "PHP_FCGI_MAX_REQUESTS" => "10000"
                     ),
                     "broken-scriptfilename" => "enable"
                 )))

conf-enabled 目录内容 #

ls conf-enabled/
10-fastcgi.conf  90-javascript-alias.conf

10-fastcgi.conf 文件内容 #

cat conf-enabled/10-fastcgi.conf 
# /usr/share/doc/lighttpd/fastcgi.txt.gz
# http://redmine.lighttpd.net/projects/lighttpd/wiki/Docs:ConfigurationOptions#mod_fastcgi-fastcgi

server.modules += ( "mod_fastcgi" )

Socket文件权限信息 #

ls -l /var/run/lighttpd/php.socket-0
srwxr-xr-x 1 www-data www-data 0 Nov  1 13:36 /var/run/lighttpd/php.socket-0

排查与解决步骤 #

• 检查PHP-FPM安装状态
  配置中使用的/bin/php7.4是CLI版本PHP，无法作为FastCGI后端处理请求。先确认系统是否安装PHP-FPM：

  dpkg -l | grep php7.4-fpm
  

  未安装则执行：

  apt update && apt install php7.4-fpm
  

  安装后启动并设置开机自启：

  systemctl start php7.4-fpm
  systemctl enable php7.4-fpm
  

• 修正FastCGI配置
  修改lighttpd.conf中的fastcgi.server配置，指向PHP-FPM默认socket路径（可通过/etc/php/7.4/fpm/pool.d/www.conf中的listen参数确认）：

  fastcgi.server = ( ".php" => ((
                        "socket" => "/run/php/php7.4-fpm.sock",
                        "broken-scriptfilename" => "enable"
                    )))
  

• 验证权限匹配
  确保www-data用户有权访问PHP-FPM socket：

  1. 打开/etc/php/7.4/fpm/pool.d/www.conf，确认listen.owner和listen.group均为www-data
  2. 检查socket权限：

     ls -l /run/php/php7.4-fpm.sock
     

     权限应为srw-rw---- 1 www-data www-data ...，不符合则修改配置后重启php7.4-fpm

• 清理无效Socket并重启服务

  rm /var/run/lighttpd/php.socket-0
  systemctl restart lighttpd
  

• 测试PHP运行
  在/var/www/html下创建test.php：

  <?php phpinfo(); ?>
  

  通过浏览器访问http://服务器IP:8078/test.php，若正常显示PHP信息则问题解决。

内容的提问来源于stack exchange，提问作者user1424074