$ yum install https://download.postgresql.org/pub/repos/yum/11/redhat/rhel-7-x86_64/pgdg-redhat11-11-2.noarch.rpm
$ yum install pgadmin4-web.noarch
$ pip install psycopg2-binary
$ pip install --upgrade pip

$ python /usr/lib/python2.7/site-packages/pgadmin4-web/setup.py

$ chown -R apache:apache /var/lib/pgadmin /var/log/pgadmin /var/log/pgadmin4

$ cat > /etc/httpd/conf.d/pgadmin4.conf << EOF
<VirtualHost *>
ServerName pgadmin.rt.ru

WSGIDaemonProcess pgadmin processes=1 threads=25
WSGIScriptAlias / /usr/lib/python2.7/site-packages/pgadmin4-web/pgAdmin4.wsgi

<Directory "/usr/lib/python2.7/site-packages/pgadmin4-web/">
WSGIProcessGroup pgadmin
WSGIApplicationGroup %{GLOBAL}
Require all granted
</Directory>
</VirtualHost>
EOF

$ systemctl enable httpd
$ systemctl start httpd

As others have said <code>lsof</code> can be used to list all the deleted files which are still on disk due to open file descriptors. However, this may be a very long list. Here is a command which lists these files sorted by ascending size in bytes:
lsof -F sn0 | tr -d '\000' | grep deleted | sed 's/^[a-z]*\([0-9]*\)n/\1 /' | sort -n

If some files are deleted but still used by some process then it's space will not be released. In this case either restart a process that is using the file or nullify the file. Its always good practice to null such files instead of deleting them. To find deleted files but are still in use by some process

lsof +L1

it will give process id and file descriptor. To null deleted file by file descriptor
echo "" > /proc/$pid/fd/$fd

Рабочая ОС - Fedora, постоянно отваливается bluetooth и, соответственно, bluetooth-мышка.

Набрав dmesg, видим следующую ошибку:
[162742.155590] Bluetooth: hci0: last event is not cmd complete (0x0f)
[162758.026567] Bluetooth: hci0: last event is not cmd complete (0x0f)
[162773.898560] Bluetooth: hci0: last event is not cmd complete (0x0f)
[162790.282573] Bluetooth: hci0: last event is not cmd complete (0x0f)
[162806.154573] Bluetooth: hci0: last event is not cmd complete (0x0f)
[162822.025571] Bluetooth: hci0: last event is not cmd complete (0x0f)

Далее, грепаем по firmware:
$ dmesg | grep -i firmware

Видим:
[52159.395988] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2
[75519.659634] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2
[78462.480546] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2
[89675.219801] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2
[95998.271165] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2

Временно устраняем проблему:
$ modprobe -r btusb
$ modprobe btusb

Лечим следующим образом:
https://github.com/lwfinger

Посмотреть текущие лимиты 'Max open files' для процесса можно так:

cat 
/proc/<pid>/limits
 | grep 'Max open files'
или так:
prlimit <pid>

Посмотреть количество открытых файлов:
cat /proc/sys/fs/file-nr