rsync 无密码传输文件

最近机器迁移，需要备份文件，但各个机器间不能穿梭，即无法通过scp来传输文件，

在运维的建议下，选用了rsync作为传输的工具。

默认情况Ubuntu安装了rsync服务，但在/etc下没有配置文件，一般情况可以copy示例文件到/etc下。

配置无帐号登录的示例如下，需要主要高亮的部分。

[mail]
    comment = public archive
    path = /tmp/mail/
    use chroot = no
#    max connections=10
    lock file = /var/lock/rsyncd
# the default for read only is yes...
    read only = no
    list = yes
    uid = service
    gid = admin
#    exclude = 
#    exclude from = 
#    include = 
#    include from =
#    auth users = service
#    secrets file = /etc/rsyncd.secrets
    strict modes = no
#    hosts allow =
#    hosts deny =
    ignore errors = no
    ignore nonreadable = yes
    transfer logging = no
#    log format = %t: host %h (%a) %o %f (%l bytes). Total %b bytes.
    timeout = 600
    refuse options = checksum dry-run
    dont compress = *.gz *.tgz *.zip *.z *.rpm *.deb *.iso *.bz2 *.tbz