I have set up an Ubuntu server at home to host a small web-page containing files I want to access from outside. All is working really well but sometimes if I wake up, the server is frozen. I can't connect via SSH, HTTP, ... I have tried to plug in a keyboard and monitor but it only shows a black screen. So I have to reboot the machine and everything is working again.
The last lines of `/var/log/syslog` are: Jan 22 10:15:01 server CRON: (www-data) CMD (php -f /var/www/ownCloud/cron.php) Jan 22 10:15:01 server CRON: (user) CMD (/home/user/cronjobs/cloudflare 1>> /home/user/cronjobs/logs/cloudflare.out 2>> /home/user/cronjobs/logs/cloudflare.err) Jan 22 10:15:28 server kernel: [244035.211772] [UFW BLOCK] IN=em1 OUT= MAC=01:00:5e:00:00:01:9c:c7:a6:ba:7c:0f:08:00 SRC=192.168.178.1 DST=126.96.36.199 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2 Jan 22 11:23:10 server rsyslogd: [origin software="rsyslogd" swVersion="7.4.4" x-pid="780" x-info="http://www.rsyslog.com"] start Jan 22 11:23:10 server rsyslogd: rsyslogd's groupid changed to 104 Jan 22 11:23:10 server rsyslogd: rsyslogd's userid changed to 101
which means the server stopped responding between 10:15 and 11:23 (when I rebooted the machine). Any ideas how to solve or investigate the problem further?