Have just executed the backup manually (without waiting it gets
scheduled by crontab). The result is good enough. It turned out was
just a network issue.

   root@gnuweeb:~# crontab -e
   No modification made
   root@gnuweeb:~# /usr/bin/env TG_BOT_TOKEN="xxxxxxx"
TG_CHANNEL_ID="-xxxxxx" php /var/www/mail.gnuweeb.org/backup.php >
/root/telegram_backup.log 2>&1
   root@gnuweeb:~# cat /root/telegram_backup.log
   exec mysqldump --default-character-set=utf8mb4 --hex-blob
-h'127.0.0.1' -P'xxxx' -u'xxxxxxx' -p'xxxxxxxx' 'gnuweeb' | gzip -9c >
'/tmp/gnuweeb_2021_05_30__09_16_30.sql.gz' 2>&1
{"ok":true,"result":{"message_id":82,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"date":1622366191,"document":{"file_name":"gnuweeb_2021_05_30__09_16_30.sql.gz","file_id":"BQACAgUAAx0ES3bxGgADUmCzV-9sipok1-emQ4vLsIAx4gSjAAI_AwACgEuZVaOdI0XGKCfdHwQ","file_unique_id":"AgADPwMAAoBLmVU","file_size":8898},"caption":"Datetime:
2021-05-30T09:16:30+00:00\nFile name:
gnuweeb_2021_05_30__09_16_30.sql.gz\nFile size: 8898 bytes\nMD5 sum:
6363e6d6c144bac530385c8e6abbbb13\nSHA1 sum:
5abc09dd14ca056a51bfdf49a92787d2a6c0e075","caption_entities":[{"offset":0,"length":9,"type":"bold"},{"offset":10,"length":25,"type":"code"},{"offset":36,"length":10,"type":"bold"},{"offset":47,"length":35,"type":"code"},{"offset":83,"length":10,"type":"bold"},{"offset":94,"length":4,"type":"code"},{"offset":105,"length":8,"type":"bold"},{"offset":114,"length":32,"type":"code"},{"offset":147,"length":9,"type":"bold"},{"offset":157,"length":40,"type":"code"}]}}
   exec mysqldump --default-character-set=utf8mb4 --hex-blob
-h'127.0.0.1' -P'xxxx' -u'xxxxxxx' -p'xxxxxxxx' 'xxxxxxx' | gzip -9c >
'/tmp/xxxxxxx_2021_05_30__09_16_30.sql.gz' 2>&1
{"ok":true,"result":{"message_id":83,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"date":1622366193,"document":{"file_name":"xxxxxxx_2021_05_30__09_16_30.sql.gz","file_id":"BQACAgUAAx0ES3bxGgADU2CzV_GM3xtu1t5XHttcHI0XU2UxAAJAAwACgEuZVZXtLZajzXHNHwQ","file_unique_id":"AgADQAMAAoBLmVU","file_size":5175},"caption":"Datetime:
2021-05-30T09:16:32+00:00\nFile name:
xxxxxxx_2021_05_30__09_16_30.sql.gz\nFile size: 5175 bytes\nMD5 sum:
c047b2395865e416a5a6699613f6cb9a\nSHA1 sum:
52a8f135138bef21aa1aeb572850928c0a87677b","caption_entities":[{"offset":0,"length":9,"type":"bold"},{"offset":10,"length":25,"type":"code"},{"offset":36,"length":10,"type":"bold"},{"offset":47,"length":40,"type":"code"},{"offset":88,"length":10,"type":"bold"},{"offset":99,"length":4,"type":"code"},{"offset":110,"length":8,"type":"bold"},{"offset":119,"length":32,"type":"code"},{"offset":152,"length":9,"type":"bold"},{"offset":162,"length":40,"type":"code"}]}}
   cd /var/vmail; tar --dereference -c gnuweeb.org | gzip -9c >
'/tmp/vmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz'
{"ok":true,"result":{"message_id":84,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"date":1622366209,"document":{"file_name":"vmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz","file_id":"BQACAgUAAx0ES3bxGgADVGCzWAABlGrvg-zwE7tqESH1-v7D6AACQQMAAoBLmVVwSalpUAw4dh8E","file_unique_id":"AgADQQMAAoBLmVU","file_size":30319753},"caption":"Datetime:
2021-05-30T09:16:37+00:00\nFile name:
vmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz\nFile size: 30319753
bytes\nMD5 sum: 3fb3da4610309c7729e143521010c68c\nSHA1 sum:
dbf944f46d17e35deaa9165c8c867e65ea02bc13","caption_entities":[{"offset":0,"length":9,"type":"bold"},{"offset":10,"length":25,"type":"code"},{"offset":36,"length":10,"type":"bold"},{"offset":47,"length":45,"type":"code"},{"offset":93,"length":10,"type":"bold"},{"offset":104,"length":8,"type":"code"},{"offset":119,"length":8,"type":"bold"},{"offset":128,"length":32,"type":"code"},{"offset":161,"length":9,"type":"bold"},{"offset":171,"length":40,"type":"code"}]}}
   cd /var/lib; tar --dereference -c mailman | gzip -9c >
'/tmp/varlib_mailman_2021_05_30__09_16_30.tar.gz'
{"ok":true,"result":{"message_id":85,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"date":1622366220,"document":{"file_name":"varlib_mailman_2021_05_30__09_16_30.tar.gz","file_id":"BQACAgUAAx0ES3bxGgADVWCzWAuN5zu-5G273m4l1w76O60aAAJCAwACgEuZVWe9bBmK96HOHwQ","file_unique_id":"AgADQgMAAoBLmVU","file_size":9438168},"caption":"Datetime:
2021-05-30T09:16:53+00:00\nFile name:
varlib_mailman_2021_05_30__09_16_30.tar.gz\nFile size: 9438168
bytes\nMD5 sum: dca9d29036c85e5079ca34dd7f84b54b\nSHA1 sum:
eeaa966491c5682d0c474fa7ff4c5de9cd9697f9","caption_entities":[{"offset":0,"length":9,"type":"bold"},{"offset":10,"length":25,"type":"code"},{"offset":36,"length":10,"type":"bold"},{"offset":47,"length":42,"type":"code"},{"offset":90,"length":10,"type":"bold"},{"offset":101,"length":7,"type":"code"},{"offset":115,"length":8,"type":"bold"},{"offset":124,"length":32,"type":"code"},{"offset":157,"length":9,"type":"bold"},{"offset":167,"length":40,"type":"code"}]}}
{"ok":true,"result":{"message_id":86,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb Backup","type":"channel"},"date":1622366221,"text":"[Time taken
for each job]\ngnuweeb_2021_05_30__09_16_30.sql.gz: 1.7395720481873
s\nxxxxxxx_2021_05_30__09_16_30.sql.gz: 1.5848047733307
s\nvmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz: 15.539685964584
s\nvarlib_mailman_2021_05_30__09_16_30.tar.gz: 11.031145095825
s\n\nTotal time: 29.895207881927 s\nWall time: 29.902309894562
s","entities":[{"offset":0,"length":25,"type":"bold"},{"offset":26,"length":36,"type":"bold"},{"offset":63,"length":15,"type":"code"},{"offset":81,"length":41,"type":"bold"},{"offset":123,"length":15,"type":"code"},{"offset":141,"length":46,"type":"bold"},{"offset":188,"length":15,"type":"code"},{"offset":206,"length":43,"type":"bold"},{"offset":250,"length":15,"type":"code"},{"offset":269,"length":11,"type":"bold"},{"offset":281,"length":15,"type":"code"},{"offset":299,"length":10,"type":"bold"},{"offset":310,"length":15,"type":"code"}]}}
{"ok":true,"result":{"message_id":87,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb Backup","type":"channel"},"date":1622366222,"text":"[File size
for each job]\ngnuweeb_2021_05_30__09_16_30.sql.gz: 8898
bytes\nxxxxxxx_2021_05_30__09_16_30.sql.gz: 5175
bytes\nvmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz: 30319753
bytes\nvarlib_mailman_2021_05_30__09_16_30.tar.gz: 9438168
bytes\n\nTotal size: 39771994
bytes","entities":[{"offset":0,"length":24,"type":"bold"},{"offset":25,"length":36,"type":"bold"},{"offset":62,"length":4,"type":"code"},{"offset":73,"length":41,"type":"bold"},{"offset":115,"length":4,"type":"code"},{"offset":126,"length":46,"type":"bold"},{"offset":173,"length":8,"type":"code"},{"offset":188,"length":43,"type":"bold"},{"offset":232,"length":7,"type":"code"},{"offset":247,"length":11,"type":"bold"},{"offset":259,"length":8,"type":"code"}]}}
{"ok":true,"result":{"message_id":88,"sender_chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"chat":{"id":-xxxxxxxx,"title":"[Internal]
GNU/Weeb
Backup","type":"channel"},"date":1622366223,"text":"=========================="}}
   root@gnuweeb:~#

Result:
   [Time taken for each job]
   gnuweeb_2021_05_30__09_16_30.sql.gz: 1.7395720481873 s
   postfixadmin_2021_05_30__09_16_30.sql.gz: 1.5848047733307 s
   vmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz: 15.539685964584 s
   varlib_mailman_2021_05_30__09_16_30.tar.gz: 11.031145095825 s

   Total time: 29.895207881927 s
   Wall time: 29.902309894562 s

   [File size for each job]
   gnuweeb_2021_05_30__09_16_30.sql.gz: 8898 bytes
   postfixadmin_2021_05_30__09_16_30.sql.gz: 5175 bytes
   vmail_gnuweeb_org_2021_05_30__09_16_30.tar.gz: 30319753 bytes
   varlib_mailman_2021_05_30__09_16_30.tar.gz: 9438168 bytes

   Total size: 39771994 bytes

--
GWML mailing list
GWML@gnuweeb.org
https://gwml.gnuweeb.org/listinfo/gwml