slackline's questions

One of my RAID1 disks failed recently. I've purchased a replacement, connected it up and formatted it as Linux RAID using cfdisk.

• New drive is /dev/sdc
• Old drive is /dev/sdd

They appear to have the same number of bytes and sectors overall but the formatted partitions differ in size...

# fdisk -l /dev/sd{c,d}
Disk /dev/sdc: 7.28 TiB, 8001563222016 bytes, 15628053168 sectors
Disk model: ST8000VN0022-2EL
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 952AC4E6-20B9-408D-83CE-AC4AEFBC1075

Device     Start         End     Sectors  Size Type
/dev/sdc1   2048 15628052479 15628050432  7.3T Linux RAID


Disk /dev/sdd: 7.28 TiB, 8001563222016 bytes, 15628053168 sectors
Disk model: ST8000VN004-2M21
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 4069B8CB-4C43-304B-B872-DDB89C0E0AA1

Device     Start         End     Sectors  Size Type
/dev/sdd1   2048 15628053134 15628051087  7.3T Linux RAID

Specificly...

/dev/sdc1   2048 15628052479 15628050432  7.3T Linux RAID
/dev/sdd1   2048 15628053134 15628051087  7.3T Linux RAID

The new partition /dev/sdc1 is smaller than the existing partition. As a consequence...

# mdadm --manage /dev/md127 --add /dev/sdc1
mdadm: Value "kimura:0" cannot be set as devname. Reason: Not POSIX compatible. Value ignored.
mdadm: /dev/sdc1 not large enough to join array

I've found a thread suggesting one (/dev/sdd which is the ST8000VN004) is using 512E to emulate 512bytes per logical sector despite being 4096 bytes per physical sector.

Now I'm wary of jumping in with resizing the existing partition on /dev/sdd1 to match that of /dev/sdc1 as this is part of a RAID1 array with three logical volumes on top.

Found a related thread but the issue there is different as they've a 3TB RAID and they want to partition a new 14TB so space isn't an issue, here my new partition is smaller than the existing.

Any thoughts or advice on how to proceed would be appreciated.

I'm trying to configure nginx to serve up FreshRSS at https://myserver/rss/ rather than https://rss.myserver/.

I've read the documentation and am trying to adapt the example nginx config.

Currently I have dokuwiki installed and working fine and a simple location defined for my users ~/www directory. I'm wondering if there is a conflict between what I have defined for DokuWiki and what I'm adding for FreshRSS.

###################################################################
## myserver.info                                                 ##
###################################################################
server {
    server_name  myserver.info;
    root   /usr/share/nginx/html/myserver;
    index doku.php;
    #####################################
    ## LetsEncrypt Certificate renewal ##
    #####################################
    # Uncomment the following two lines when renewing certificates (reverse once done!)
    # listen 80;
    # listen [::]:80;

    # LetsEncrypt : ACME challenge
    location ^~ /.well-known/acme-challenge/ {
        default_type "text/plain";
        root /var/lib/letsencrypt;
    }

    ## LestEncrypt : Certificates
    ssl_certificate /etc/letsencrypt/live/myserver.info/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/myserver.info/privkey.pem;
    ssl_trusted_certificate /etc/letsencrypt/live/myserver.info/chain.pem;



    #####################################
    ## Normal server config            ##
    #####################################
    # Comment the following lines when renewing certificates (reverse once done!)
    listen 443 ssl http2;
    listen [::]:443 ssl http2;

    #####################################
    ## Security Headers                ##
    #####################################
    # Add Content Security Policy (see https://lollyrock.com/posts/content-security-policy/)
    # but currently using a striped form [email protected] suggested and
    # an option to block X-frame (see https://infosec.mozilla.org/guidelines/web_security#x-frame-options)
    add_header Content-Security-Policy  "default-src 'self' always; frame-ancestors 'none'; img-src *";
    # Add Strict Transport Security (see https://infosec.mozilla.org/guidelines/web_security#http-strict-transport-security
    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload;";
    add_header X-Content-Type-Options "nosniff";
    add_header Referrer-Policy "no-referrer";

    #####################################
    ## Dokuwiki                        ##
    #####################################
    # Remember to comment the below out when you're installing DokuWiki, and uncomment it when you're done.
    location ~ /(data/|conf/|bin/|inc/|install.php) { deny all; } # secure Dokuwiki

    location ~^/\.ht { deny all; } # also secure the Apache .htaccess files
    location @dokuwiki {
        #rewrites "doku.php/" out of the URLs if you set the userewrite setting to .htaccess in dokuwiki config page
        rewrite ^/_media/(.*) /lib/exe/fetch.php?media=$1 last;
        rewrite ^/_detail/(.*) /lib/exe/detail.php?media=$1 last;
        rewrite ^/_export/([^/]+)/(.*) /doku.php?do=export_$1&id=$2 last;
        rewrite ^/(.*) /doku.php?id=$1&$args last;
    }
    location / { try_files $uri $uri/ @dokuwiki; }
    location ~ \.php$ {
        try_files $uri =404;
        fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
        fastcgi_index index.php;
        include fastcgi.conf;
    }

    #####################################
    ## User '~/www/'                   ##
    #####################################
    location ~ ^/~(.+?)(/.*)?$ {
        alias /home/$1/www$2;
        index index.html index.htm;
        autoindex on;
    }
    ######################################
    ## FreshRSS (https://freshrss.org/) ##
    ######################################
    location ~ ^/rss/.+?\.php(/.*)?$ {
        alias /usr/share/webapps/freshrss/p/;
        fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
    # By default, the variable PATH_INFO is not set under PHP-FPM
    # But FreshRSS API greader.php need it. If you have a “Bad Request” error, double check this var!
    # NOTE: the separate $path_info variable is required. For more details, see:
    # https://trac.nginx.org/nginx/ticket/321
        set $path_info $fastcgi_path_info;
        fastcgi_param PATH_INFO $path_info;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }
}

The files under /usr/share/webapps/freshrss/p/ are...

root@vps410177/usr/share/webapps/freshrss 84 l /usr/share/webapps/freshrss/p/
total 68K
drwxr-xr-x  6 http http 4.0K Oct  5 07:09 .
drwxr-xr-x  8 root root 4.0K Oct  5 07:09 ..
drwxr-xr-x  2 http http 4.0K Oct  5 07:09 api
-rw-r--r--  1 http http 2.7K Oct  5 07:08 ext.php
-rw-r--r--  1 http http  18K Oct  5 07:08 favicon.ico
-rw-r--r--  1 http http 1.6K Oct  5 07:08 f.php
-rw-r--r--  1 root root 1.2K Oct  5 07:08 .htaccess
drwxr-xr-x  2 http http 4.0K Oct  5 07:09 i
-rw-r--r--  1 http http  774 Oct  5 07:08 index.html
-rw-r--r--  1 http http   26 Oct  5 07:08 robots.txt
drwxr-xr-x  2 http http 4.0K Oct  5 07:09 scripts
drwxr-xr-x 16 http http 4.0K Oct  5 07:09 themes
-rw-r--r--  1 http http 1.7K Oct  5 07:08 Web.config

If I go to https://myserver.info/rss/ I'm redirected to the Dokuwiki site and informed that the topic does not exist. If I try https://myserver.info/rss/f.php I get a 404 not found and I think this is because of the location definition...

    location ~ \.php$ {
        try_files $uri =404;
        fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
        fastcgi_index index.php;
        include fastcgi.conf;
    }

...which is conflicting with the FreshRSS alias which has location ~ ^/rss/.+?\.php(/.*)?$ {...} ...

    ######################################
    ## FreshRSS (https://freshrss.org/) ##
    ######################################
    location ~ ^/rss/.+?\.php(/.*)?$ {
        alias /usr/share/webapps/freshrss/p/;
        fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
    # By default, the variable PATH_INFO is not set under PHP-FPM
    # But FreshRSS API greader.php need it. If you have a “Bad Request” error, double check this var!
    # NOTE: the separate $path_info variable is required. For more details, see:
    # https://trac.nginx.org/nginx/ticket/321
        set $path_info $fastcgi_path_info;
        fastcgi_param PATH_INFO $path_info;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }

I found this solution on nesting location so have tried...

        location ~ \.php$ {
        #####################################################################
        ## FreshRSS (https://freshrss.org/)                                ##
        #####################################################################
                location ~ ^/rss/.+?\.php(/.*)?$ {
                    alias /usr/share/webapps/freshrss/p/;
                    fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
                    fastcgi_split_path_info ^(.+\.php)(/.*)$;
        # By default, the variable PATH_INFO is not set under PHP-FPM
        # But FreshRSS API greader.php need it. If you have a “Bad Request” error, double check this var!
        # NOTE: the separate $path_info variable is required. For more details, see:
        # https://trac.nginx.org/nginx/ticket/321
                    set $path_info $fastcgi_path_info;
                    fastcgi_param PATH_INFO $path_info;
                    include fastcgi_params;
                    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
                }
            try_files $uri =404;
            fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
            fastcgi_index index.php;
            include fastcgi.conf;
        }

...but with the same results as described above if I go to https://myserver/rss/ if they are not nested, but if I go to https://myserver/rss/f.php I get a 502 Bad Gateway error which is some progress but I'm unsure where I've gone wrong.

Is there a way to configure Nginx to serve up PHP from different locations/aliases?

EDIT :

In light of feedback from @Derek Held I've attempted to set a locationas follows using root rather than alias under its own block (and not nested within the dokuwiki configuration)...

        location ~ ^/rss/$ {
                root /usr/share/webapps/freshrss/p/;
                fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
                fastcgi_split_path_info ^(.+\.php)(/.*)$;
        # By default, the variable PATH_INFO is not set under PHP-FPM
        # But FreshRSS API greader.php need it. If you have a “Bad Request” error, double check this var!
        # NOTE: the separate $path_info variable is required. For more details, see:
        # https://trac.nginx.org/nginx/ticket/321
                 set $path_info $fastcgi_path_info;
                 fastcgi_param PATH_INFO $path_info;
                 include fastcgi_params;
                 fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;                   
        }

But without success pointing to https://myserver/rss/ and https://myserver/rss/f.php gives 502 Bad Gateway (even though perimissions are for the user that nginx is running as).

I'm attempting to get Brother HL-L2301-D printer running under Gentoo.

I've downloaded the RPM and installed it under Gentoo. The device is detected and I've set up a udev rule to make it available at /dev/usb/lp0, although it now appears there not as a symbolic link as it did yesterday but is still present at that location

# lsusb | grep -i brother
Bus 001 Device 100: ID 04f9:009a Brother Industries, Ltd HL-L2310D series
# l /dev/usb/lp0 
crw-rw---- 1 root lp 180, 0 Apr 21 10:24 /dev/usb/lp0

I've tried adding the printer in two ways after reading this thread that suggested using the usb://Brother/HL-L2310D%20series?serial=### rather than usb://dev/usb/lp0...

# lpadmin -p Chompy -E -v usb://Brother/HL-L2310D%20series?serial=E78096L9N400161 -i /usr/share/ppd/cupsfilters/brother-HLL2310D-cups-en.ppd -L "Study"
# lpadmin -p Chompy2 -E -v usb://dev/usb/lp0 -P /usr/share/ppd/brother/brother-HLL2310D-cups-en.ppd

The printer is turned on and lights indicate its "Ready", both Chompy and Chompy2 (daughter chose the name, quite perceptive for 6yo!) are listed in the CUPS WebUI and yet if I try to print a test page to either I'm told...

Processing - "Waiting for printer to become available."

Checking with lstat

# lpstat -o "Chompy" -p -l
Chompy-22               root              1024   Tue 21 Apr 2020 10:25:17 BST
printer Chompy now printing Chompy-22.  enabled since Tue 21 Apr 2020 10:25:17 BST
    Waiting for printer to become available.

Same happens if I try using Chompy2.

Stumped as to what to try next, any suggestions would be gratefully received. I'm keen to get this working and then share it on the network.

Continuing attempting to configure nginx to use a reverse proxy to radicale that is running on local host and I'm now getting SSL errors having followed the documentation on proxy I created my own SSL certificates.

The relevant section of my nginx configuration is

location /radicale/ {                                                         
          proxy_pass                    http://127.0.0.1:9468/;                     
          #proxy_pass                   http://46.105.31.182:9468/;                 
          proxy_set_header              X-Script-Name /radicale;                    
          proxy_set_header              X-Forwarded-For $proxy_add_x_forwarded_for; 
          proxy_set_header              X-Remote-User $remote_user;                 
          auth_basic                    "Radicale - Password Required";             
          auth_basic_user_file          /etc/radicale/users;                        
          proxy_ssl_verify              on;                                         
          proxy_ssl_certificate         /etc/radicale/client_cert.pem;              
          proxy_ssl_certificate_key     /etc/radicale/client_key.pem;               
          proxy_ssl_trusted_certificate /etc/radicale/server_cert.pem;              
}                                                                             

...and my radicale config for SSL certificates is...

[server]
hosts = 127.0.0.1:9468
ssl = true
certificate = /etc/radicale/server_cert.pem
key = /etc/radicale/server_key.pem
certificate_authority = /etc/radicale/client_cert.pem

[auth]
type = http_x_remote_user
htpasswd_filename = /etc/radicale/users
htpasswd_encryption = bcrypt

If I go to the site https://####/radicale I'm prompted for username and password for authentication, but nginx then returns the following error...

upstream prematurely closed connection while reading response header from upstream, client: 62.253.154.162, server: #####, request: "GEET /radicale/ HTTP/2.0", upstream: "http://127.0.0.1:9468/", host: "####"

...and upstream Radicale reports...

ERROR: An exception occurred during request: SSL handshake failed: [SSL: HTTP_REQUEST] http request (_ssl.c:1076)

If I disable SSL between the reverse proxy on Radicale and nginx then its not a problem, I can access the WebUI https://####/radicale and I can login. But if I enable it then going to https://####/radicale and I get a pop-up box asking me for username/password and the browser reports 502 Bad Gateway and the above errors occur again.

I do have LetsEncrypt certificates in place and working on my domain could this be causing some sort of conflict with the SSL certificates being used for the reverse proxy?

Before getting started I configured Radicale to run on its own without any security and could access the WebUI on the specified IP:port so things were working. I then wanted to use a reverse proxy and SSL certificates to make things more secure so turned to their clear and simple documentation.

I've added the following to my server{...} definition under /etc/nginx/nginx.conf...

       #####################################################################
       ## Radicle (https://radicale.org/proxy/)                           ##
       #####################################################################
       location /radicale/ {                                                
           proxy_pass           http://localhost:9468/;
           proxy_set_header     X-Script-Name /radicale;                    
           proxy_set_header     X-Forwarded-For $proxy_add_x_forwarded_for; 
           proxy_set_header     X-Remote-User $remote_user;                 
           auth_basic           "Radicale - Password Required";             
           auth_basic_user_file /etc/radicle/htpasswd;                      
           proxy_ssl_certificate         /etc/radicale/client_cert.pem;     
           proxy_ssl_certificate_key     /etc/radicale/client_key.pem;      
           proxy_ssl_trusted_certificate /etc/radicale/server_cert.pem;     
       }                                                                    

...and have generated all the certificates. If I go to https://example.org/radicale/ I'm asked to log in and can do so with my user credentials. Unfortunately I then get 403: Forbidden :-/

My /etc/radicale/conf is as follows

[server]
[server]
hosts = 127.0.0.1:9468
ssl = True
certificate = /etc/radicale/server_cert.pem
key = /etc/radicale/server_key.pem
certificate_authority = /etc/radicale/client_cert.pem
[encoding]
[auth]
type = http_x_remote_user
htpasswd_filename = /etc/radicale/users
htpasswd_encryption = bcrypt
[rights]
[storage]
[web]
[logging]
[headers]

(if an option isn't listed its the default).

First thought was its a permissions issue on the filesystem_folder = /var/lib/radicale/collections so I modified these to be radicale:http (as nginx runs as http on this Arch Linux system)...

# l /var/lib/radicale/
total 12K
drwxrwxr-x  3 radicale http 4.0K Aug  7 07:35 .
drwxr-xr-x 25 root     root 4.0K Aug 12 08:07 ..
drwxrwxr-x  3 radicale http 4.0K Aug  7 08:18 collections
# l /var/lib/radicale/collections/
total 12K
drwxrwxr-x 3 radicale http 4.0K Aug  7 08:18 .
drwxrwxr-x 3 radicale http 4.0K Aug  7 07:35 ..
drwxrwxr-x 3 radicale http 4.0K Aug  7 08:18 collection-root
-rwxrwxr-x 1 radicale http    0 Aug  7 08:18 .Radicale.lock
# l /var/lib/radicale/collections/collection-root/
total 12K
drwxrwxr-x 3 radicale http 4.0K Aug  7 08:18 .
drwxrwxr-x 3 radicale http 4.0K Aug  7 08:18 ..
drwxrwxr-x 4 radicale http 4.0K Aug  7 08:20 user
# l /var/lib/radicale/collections/collection-root/user/
total 16K
drwxrwxr-x 4 radicale http 4.0K Aug  7 08:20 .
drwxrwxr-x 3 radicale http 4.0K Aug  7 08:18 ..
drwxrwxr-x 2 radicale http 4.0K Aug  7 08:19 86487dd0-1ca2-8183-b1b8-0bc7933792d2
drwxrwxr-x 2 radicale http 4.0K Aug  7 13:46 bd050325-a411-5d0a-625b-d8569b442441
# l /var/lib/radicale/collections/collection-root/user/*
/var/lib/radicale/collections/collection-root/user/86487dd0-1ca2-8183-b1b8-0bc7933792d2:
total 12K
drwxrwxr-x 2 radicale http 4.0K Aug  7 08:19 .
drwxrwxr-x 4 radicale http 4.0K Aug  7 08:20 ..
-rwxrwxr-x 1 radicale http  165 Aug  7 08:19 .Radicale.props

/var/lib/radicale/collections/collection-root/user/bd050325-a411-5d0a-625b-d8569b442441:
total 12K
drwxrwxr-x 2 radicale http 4.0K Aug  7 13:46 .
drwxrwxr-x 4 radicale http 4.0K Aug  7 08:20 ..
-rwxrwxr-x 1 radicale http  216 Aug  7 13:46 .Radicale.props

But no joy, still get 403 : Forbidden, so now I'm stumped as to what to try.

Any suggestions would be gratefully received.

I've installed Wordpress under ArchLinux on my VPS, configured the SQL backend and edited /usr/share/webapps/wordpress/wp-config.php. Unfortunately on trying to access pages I'm getting...

2019/06/14 06:44:12 [error] 20812#20812: *394 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught Error: Call to undefined function mysql_connect() in /usr/share/webapps/wordpress/wp-includes/wp-db.php:1645
Stack trace:
#0 /usr/share/webapps/wordpress/wp-includes/wp-db.php(639): wpdb->db_connect()
#1 /usr/share/webapps/wordpress/wp-includes/load.php(427): wpdb->__construct('wp-user', 'pc&0wC<k%:o<AuI...', 'wordpress', 'localhost')
#2 /usr/share/webapps/wordpress/wp-settings.php(120): require_wp_db()
#3 /usr/share/webapps/wordpress/wp-config.php(90): require_once('/usr/share/weba...')
#4 /usr/share/webapps/wordpress/wp-load.php(37): require_once('/usr/share/weba...')
#5 /usr/share/webapps/wordpress/wp-blog-header.php(13): require_once('/usr/share/weba...')
#6 /usr/share/webapps/wordpress/index.php(17): require('/usr/share/weba...')
#7 {main}
thrown in /usr/share/webapps/wordpress/wp-includes/wp-db.php on line 1645" while reading response header from upstream, client:...

Searching around this appears to happen under PHP when its attempting to use the mysql module rather than mysqli (found threads here and here).

I've enabled mysqli in /etc/php/php.ini

extension=mysqli

...and the module is loaded...

php -m
[PHP Modules]
Core
ctype
curl
date
dom
fileinfo
filter
hash
json
libxml
mbstring
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
Phar
posix
readline
Reflection
session
SimpleXML
SPL
standard
tokenizer
xml
xmlreader
xmlwriter
zip
zlib
[Zend Modules]

Reading through /usr/share/webapps/wordpress/wp-includes/wp-db.php around the offending line (1645) it looks to me as though there are a series of if{} else{} statements starting on line 1589 which checks to see if use_mysqli is being used,this fails and as there is no mysql module in they was removed in PHP7 and mysqli should instead be used.

grep '\$this->use_mysqli' /usr/share/webapps/wordpress/wp-includes/wp-db.php -A100 -n | grep 1589 -A100
1589:           if ( $this->use_mysqli ) {
1590-                   $this->dbh = mysqli_init();
1591-
1592-                   $host    = $this->dbhost;
1593-                   $port    = null;
1594-                   $socket  = null;
1595-                   $is_ipv6 = false;
1596-
1597-                   if ( $host_data = $this->parse_db_host( $this->dbhost ) ) {
1598-                           list( $host, $port, $socket, $is_ipv6 ) = $host_data;
1599-                   }
1600-
1601-                   /*
1602-                    * If using the `mysqlnd` library, the IPv6 address needs to be
1603-                    * enclosed in square brackets, whereas it doesn't while using the
1604-                    * `libmysqlclient` library.
1605-                    * @see https://bugs.php.net/bug.php?id=67563
1606-                    */
1607-                   if ( $is_ipv6 && extension_loaded( 'mysqlnd' ) ) {
1608-                           $host = "[$host]";
1609-                   }
1610-
1611-                   if ( WP_DEBUG ) {
1612-                           mysqli_real_connect( $this->dbh, $host,    $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
1613-                   } else {
1614-                           @mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
1615-                   }
1616-
1617-                   if ( $this->dbh->connect_errno ) {
1618-                           $this->dbh = null;
1619-
1620-                           /*
1621-                            * It's possible ext/mysqli is misconfigured. Fall back to ext/mysql if:
1622-                             *  - We haven't previously connected, and
1623-                             *  - WP_USE_EXT_MYSQL isn't set to false, and
1624-                             *  - ext/mysql is loaded.
1625-                             */
1626-                           $attempt_fallback = true;
1627-
1628-                           if ( $this->has_connected ) {
1629-                                   $attempt_fallback = false;
1630-                           } elseif ( defined( 'WP_USE_EXT_MYSQL' ) && ! WP_USE_EXT_MYSQL ) {
1631-                                   $attempt_fallback = false;
1632-                           } elseif ( ! function_exists( 'mysql_connect' ) ) {
1633-                                   $attempt_fallback = false;
1634-                           }
1635-
1636-                           if ( $attempt_fallback ) {
1637:                                   $this->use_mysqli = false;
1638-                                   return $this->db_connect( $allow_bail );
1639-                           }
1640-                   }
1641-           } else {
1642-                   if ( WP_DEBUG ) {
1643-                           $this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
1644-                   } else {
1645-                           $this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
1646-                   }
1647-           }

This fails because, looking further back through /usr/share/webapps/wordpress/wp-includes/wp-db.php I can see $is_mysql is set to null on line 564 and $use_mysqli is set to false which explains why the test to see if use_mysqli is being used fails and instead connect_mysql() is being attempted...

grep 'public \$is_mysql = null' /usr/share/webapps/wordpress/wp-includes/wp-db.php -A30 -n
564:    public $is_mysql = null;
565-
566-    /**
567-     * A list of incompatible SQL modes.
568-     *
569-     * @since 3.9.0
570-     * @var array
571-     */
572-    protected $incompatible_modes = array(
573-            'NO_ZERO_DATE',
574-            'ONLY_FULL_GROUP_BY',
575-            'STRICT_TRANS_TABLES',
576-            'STRICT_ALL_TABLES',
577-            'TRADITIONAL',
578-    );
579-
580-    /**
581-     * Whether to use mysqli over mysql.
582-     *
583-     * @since 3.9.0
584-     * @var bool
585-     */
586-    private $use_mysqli = false;

Given mysql has been removed since PHP7 and is not a listed possible module in /etc/php/php.ini I'm surprised $use_mysqli = false on a fresh install. I've tried setting it to true and after restarting php-fpm.service now get another error and enter the if ( $this->$use_mysqli){...} section only to fail on the first call to $this->dbh = mysqli_init()...

2019/06/14 07:10:25 [error] 1439#1439: *1 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught Error: Call to undefined function mysqli_init() in /usr/share/webapps/wordpress/wp-includes/wp-db.php:1591
Stack trace:
#0 /usr/share/webapps/wordpress/wp-includes/wp-db.php(640): wpdb->db_connect()
#1 /usr/share/webapps/wordpress/wp-includes/load.php(427): wpdb->__construct('wp-user', 'pc&0wC<k%:o<AuI...', 'wordpress', 'localhost')
#2 /usr/share/webapps/wordpress/wp-settings.php(120): require_wp_db()
#3 /usr/share/webapps/wordpress/wp-config.php(90): require_once('/usr/share/weba...')
#4 /usr/share/webapps/wordpress/wp-load.php(37): require_once('/usr/share/weba...')
#5 /usr/share/webapps/wordpress/wp-blog-header.php(13): require_once('/usr/share/weba...')
#6 /usr/share/webapps/wordpress/index.php(17): require('/usr/share/weba...')
#7 {main}
  thrown in /usr/share/webapps/wordpress/wp-includes/wp-db.php on line    1591" while reading response header from upstream, client:

I'm not adverse to modifying configuration but the impression I had from Arch Wiki : Wordpress article is that this level of tinkering is not required. Can anyone advise on where I might have gone wrong.

EDIT

mysqli section from phpinfo()

mysqli
MysqlI Support  enabled
Client API library version  mysqlnd 5.0.12-dev - 20150407 - $Id: 7cc7cc96e675f6d72e5cf0f267f48e167c2abb23 $
Active Persistent Links     0
Inactive Persistent Links   0
Active Links    0
Directive   Local Value Master Value
mysqli.allow_local_infile   Off Off
mysqli.allow_persistent On  On
mysqli.default_host no value    no value
mysqli.default_port 3306    3306
mysqli.default_pw   no value    no value
mysqli.default_socket   /run/mysqld/mysqld.sock /run/mysqld/mysqld.sock
mysqli.default_user no value    no value
mysqli.max_links    Unlimited   Unlimited
mysqli.max_persistent   Unlimited   Unlimited
mysqli.reconnect    Off Off
mysqli.rollback_on_cached_plink Off Off

EDIT2 : Its suggested that php-fpm wasn't loading the mysqli module, I've now checked and it appears to...

$ php-fpm -m
[PHP Modules]
cgi-fcgi
Core
ctype
curl
date
dom
fileinfo
filter
hash
json
libxml
mbstring
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
pdo_mysql
Phar
posix
readline
Reflection
session
SimpleXML
SPL
standard
tokenizer
xml
xmlreader
xmlwriter
zip
zlib

[Zend Modules]