When starting tor (systemctl restart tor) it said no issue/nothing, but tor was not running:

$ systemctl status tor
* tor.service - Anonymizing overlay network for TCP
Loaded: loaded (/usr/lib/systemd/system/tor.service; enabled; vendor preset: disabled)
Active: failed (Result: start-limit) since Sat 2018-05-19 11:58:35 CEST; 9s ago
Process: 3211 ExecStart=/usr/bin/tor --runasdaemon 0 --defaults-torrc /usr/share/tor/defaults-torrc -f /etc/tor/torrc (code=exited, status=1/FAILURE)
Process: 3210 ExecStartPre=/usr/bin/tor --runasdaemon 0 --defaults-torrc /usr/share/tor/defaults-torrc -f /etc/tor/torrc --verify-config (code=exited, status=0/SUCCESS)
Main PID: 3211 (code=exited, status=1/FAILURE)

May 19 11:58:34 localhost.localdomain systemd[1]: tor.service: main process exited, code=exited, status=1/FAILURE
May 19 11:58:34 localhost.localdomain systemd[1]: Unit tor.service entered failed state.
May 19 11:58:34 localhost.localdomain systemd[1]: tor.service failed.
May 19 11:58:35 localhost.localdomain systemd[1]: tor.service holdoff time over, scheduling restart.
May 19 11:58:35 localhost.localdomain systemd[1]: start request repeated too quickly for tor.service
May 19 11:58:35 localhost.localdomain systemd[1]: Failed to start Anonymizing overlay network for TCP.
May 19 11:58:35 localhost.localdomain systemd[1]: Unit tor.service entered failed state.
May 19 11:58:35 localhost.localdomain systemd[1]: tor.service failed.
$ journalctl -xe
May 19 12:00:16 localhost.localdomain postfix/cleanup[2943]: 51C743291: message-id=<[email protected]>
May 19 12:00:16 localhost.localdomain postfix/cleanup[2943]: warning: 51C743291: write queue file: No space left on device
May 19 12:00:16 localhost.localdomain postfix/pickup[32460]: warning: maildrop/AB9E13328: error writing 51C743291: queue file write error
May 19 12:00:16 localhost.localdomain postfix/pickup[32460]: warning: 5373D3291: message has been queued for 13 days
May 19 12:00:16 localhost.localdomain postfix/pickup[32460]: 5373D3291: uid=0 from=<root>
$ df -h
shows i am out of disk space.

So i shown largest directories on the filesystem:
du -h --max-depth=2 /|sort -h

Deleted large /var/swap.1 which was 1GB large and restarted tor, now with success. I think that swap file will be created again after reboot.