问nginx日志无法保存，第二天会被清除，不知道是为什么？

我昨天开启了nginx日志功能，并也看到了生成的日志。但我今天凌晨的时候发现昨天的日志内容没有了。我也并没有在log目录中看任何诸如access.log.2018.02.12这样类似格式的文件。这让我很担心，不知道是配置方面的问题，还是被黑客攻击了。把我日志清除了。我nginx开启日志的配置如下：

user root;

worker_processes 4;

#error_log /dev/null;

error_log logs/error.log;

#error_log logs/error.log notice;

#error_log logs/error.log info;

pid conf/nginx.pid;

worker_rlimit_nofile 1024;

events {

use epoll;

worker_connections 1024;

}

http {

include mime.types;

default_type application/octet-stream;

include proxy.conf;

log_format yundns_log '$server_name $remote_addr [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"';

log_format main '$remote_addr - $remote_user [$time_local] "$request" '

# '$status $body_bytes_sent "$http_referer" '

# '"$http_user_agent" "$http_x_forwarded_for"';

access_log logs/access.log main;

server_tokens off;

sendfile on;

tcp_nopush on;

server_names_hash_bucket_size 256;

client_header_buffer_size 256k;

#large_client_header_buffers 4 32k;

large_client_header_buffers 4 256k;

client_body_buffer_size 256k;

client_header_timeout 3m;

client_body_timeout 3m;

send_timeout 3m;

client_max_body_size 50m;

keepalive_timeout 120;

fastcgi_intercept_errors on;

fastcgi_connect_timeout 300;

fastcgi_send_timeout 300;

fastcgi_read_timeout 300;

#fastcgi_buffer_size 64k;

#fastcgi_buffers 8 64k;

#fastcgi_busy_buffers_size 128k;

#fastcgi_temp_file_write_size 128k;

fastcgi_buffer_size 128k;

fastcgi_buffers 4 256k;

fastcgi_busy_buffers_size 256k;

fastcgi_temp_file_write_size 256k;

gzip on;

gzip_min_length 1k;

gzip_buffers 4 16k;

gzip_http_version 1.0;

gzip_comp_level 2;

gzip_types text/plain application/x-javascript text/css application/xml;

gzip_vary on;

server {

listen 80;

server_name image.coolcarstime.com image1.coolcarstime.com;

#access_log off;

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