Error: file_put_contents(): Only 0 of 55 bytes written, possibly out of free disk space

#0 [internal function]: cmg_exceptionErrorHandler(2, 'file_put_conten...', '/var/www/www-gi...', 17, Array)
#1 /var/www/www-giunti-it/public_html/camargue/src/cmg/Cron.php(17): file_put_contents('/tmp/cron.txt', 'Restarting: 201...')
#2 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(293): mod_cmg_Cron->listener_check(NULL)
#3 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(74): cmg_Mod::_trigger('cmg/Process', 'startup', NULL, false)
#4 /var/www/www-giunti-it/public_html/camargue/src/cmg/Process.php(20): cmg_Mod->trigger('startup')
#5 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(293): mod_cmg_Process->listener_onLoad(NULL)
#6 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(74): cmg_Mod::_trigger('cmg/Process', 'load', NULL, false)
#7 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(218): cmg_Mod->trigger('load')
#8 /var/www/www-giunti-it/public_html/camargue/src/cmg/Mod.php(105): cmg_Mod::_load('cmg/Process')
#9 /var/www/www-giunti-it/public_html/camargue/src/cmg/camargue.php(5324): cmg_Mod::_get('cmg/Process', NULL)
#10 /var/www/www-giunti-it/public_html/camargue/src/cmg/camargue.php(4366): Cmg::mod('cmg/Process')
#11 /var/www/www-giunti-it/public_html/index.php(4): Cmg::hiYo('/camargue/src', '24')
#12 {main}

Fatal error: Uncaught ErrorException: Unknown: open(/var/lib/php/sessions/sess_vpqrcjn03qk2cggab5ql3kbme4, O_RDWR) failed: No space left on device (28) in Unknown:0 Stack trace: #0 [internal function]: cmg_exceptionErrorHandler(2, 'Unknown: open(/...', 'Unknown', 0, NULL) #1 {main} thrown in Unknown on line 0