Koha error

The following fatal error has occurred:

Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) at /usr/share/koha/lib/C4/Context.pm line 666.
Compilation failed in require at /usr/share/koha/lib/C4/Circulation.pm line 25.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Circulation.pm line 25.
Compilation failed in require at /usr/share/koha/lib/C4/Overdues.pm line 24.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Overdues.pm line 24.
Compilation failed in require at /usr/share/koha/lib/C4/Members.pm line 27.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Members.pm line 27.
Compilation failed in require at /usr/share/koha/lib/C4/Auth.pm line 31.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Auth.pm line 31.
Compilation failed in require at /usr/share/koha/opac/cgi-bin/opac/opac-detail.pl line 24.
BEGIN failed--compilation aborted at /usr/share/koha/opac/cgi-bin/opac/opac-detail.pl line 24.