backuppc 服务器能够以 root 身份登录远程机器并备份它们，但是如果我以 backuppc 用户身份登录并尝试使用相同的密钥 ssh 进入这些机器，则该密钥将被拒绝，并显示以下调试输出：
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /var/lib/BackupPC/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to XXX.XXXXXX.com [XX.XXX.XX.XX] port 222.
debug1: Connection established.
debug1: identity file /var/lib/BackupPC/.ssh/identity type -1
debug1: identity file /var/lib/BackupPC/.ssh/identity-cert type -1
debug3: Not a RSA1 key file /var/lib/BackupPC/.ssh/id_rsa.
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace …