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rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1518) [generator=3.0.9]

The server does not have write permission. Modify uid and GID in rsyncd.conf

Because the directory needs Rsync to access, after an error occurs, you can view the log file of the directory and prompt: insufficient permissions

Error causes
1 > The user specified in the server configuration file and the directory specified by the module belong to different groups

2> The directory group specified by the server module has no permission

Solution
modify the owner group of the directory specified by the module to uid GID specified in the configuration file

[ root@nfs01 ~]#The users and groups specified in chown rsync.rsync/backup configuration file

If it can’t be solved, please refer to: Rsync FAQ