问题原因：
- OpenSSL7.0以上禁用了dsa加密，推荐使用rsa
解决方案：
-
删除原先的.ssh文件
rm -rf .ssh -
ssh-keygen -t rsa ssh-copy-id username@userip
心路历程：
先说遇到bug的操作：
ssh-keygen -t dsa
ssh-copy-id username:userip
然后一顿Google，学会看以调试运行ssh
ssh -vvv username@userip
以下是debug信息：
OpenSSH_8.8p1, OpenSSL 1.0.2k-fips 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug2: resolve_canonicalize: hostname 10.188.43.140 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/home/monitor/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/home/monitor/.ssh/known_hosts2'
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug3: ssh_connect_direct: entering
debug1: Connecting to 10.188.43.140 [10.188.43.140] port 22.
debug3: set_sock_tos: set socket 3 IP_TOS 0x48
debug1: Connection established.
debug1: identity file /home/monitor/.ssh/id_rsa type -1
debug1: identity file /home/monitor/.ssh/id_rsa-cert type -1
debug1: identity file /home/monitor/.ssh/id_dsa type 1
debug1: identity file /home/monitor/.ssh/id_dsa-cert type -1
debug1: identity file /home/monitor/.ssh/id_ecdsa type -1
debug1: identity file /home/monitor/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/monitor/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/monitor/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/monitor/.ssh/id_ed25519 type -1
debug1: identity file /home/monitor/.ssh/id_ed25519-cert type -1
debug1: identity file /home/monitor/.ssh/id_ed25519_sk type -1
debug1: identity file /home/monitor/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/monitor/.ssh/id_xmss type -1
debug1: identity file /home/monitor/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.8
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.8
debug1: compat_banner: match: OpenSSH_8.8 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.188.43.140:22 as 'monitor'
debug3: record_hostkey: found key type ED25519 in file /home/monitor/.ssh/known_hosts:1
debug3: record_hostkey: found key type RSA in file /home/monitor/.ssh/known_hosts:2
debug3: record_hostkey: found key type ECDSA in file /home/monitor/.ssh/known_hosts:3
debug3: load_hostkeys_file: loaded 3 keys from 10.188.43.140
debug1: load_hostkeys: fopen /home/monitor/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug3: order_hostkeyalgs: have matching best-preference key type ssh-ed25519-cert-v01@openssh.com, using HostkeyAlgorithms verbatim
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ssh-ed25519@openssh.com,sk-ecdsa-sha2-nistp256@openssh.com,rsa-sha2-512,rsa-sha2-256
debug2: ciphers ctos: aes256-ctr,aes192-ctr,aes128-ctr
debug2: ciphers stoc: aes256-ctr,aes192-ctr,aes128-ctr
debug2: MACs ctos: hmac-sha1
debug2: MACs stoc: hmac-sha1
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256
debug2: host key algorithms: rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: aes256-ctr,aes192-ctr,aes128-ctr
debug2: ciphers stoc: aes256-ctr,aes192-ctr,aes128-ctr
debug2: MACs ctos: hmac-sha1
debug2: MACs stoc: hmac-sha1
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: aes256-ctr MAC: hmac-sha1 compression: none
debug1: kex: client->server cipher: aes256-ctr MAC: hmac-sha1 compression: none
debug3: send packet: type 34
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(2048<8192<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug3: receive packet: type 31
debug1: SSH2_MSG_KEX_DH_GEX_GROUP received
debug2: bits set: 4141/8192
debug3: send packet: type 32
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: receive packet: type 33
debug1: SSH2_MSG_KEX_DH_GEX_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:lHp7IX/CtUT0OCMI/3iLkICLmnKtWrgTMsEoVuRTML8
debug3: record_hostkey: found key type ED25519 in file /home/monitor/.ssh/known_hosts:1
debug3: record_hostkey: found key type RSA in file /home/monitor/.ssh/known_hosts:2
debug3: record_hostkey: found key type ECDSA in file /home/monitor/.ssh/known_hosts:3
debug3: load_hostkeys_file: loaded 3 keys from 10.188.43.140
debug1: load_hostkeys: fopen /home/monitor/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host '10.188.43.140' is known and matches the ED25519 host key.
debug1: Found key in /home/monitor/.ssh/known_hosts:1
debug2: bits set: 4097/8192
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 4294967296 blocks
debug1: Skipping ssh-dss key /home/monitor/.ssh/id_dsa - corresponding algo not in PubkeyAcceptedAlgorithms
debug1: Will attempt key: /home/monitor/.ssh/id_rsa
debug1: Will attempt key: /home/monitor/.ssh/id_ecdsa
debug1: Will attempt key: /home/monitor/.ssh/id_ecdsa_sk
debug1: Will attempt key: /home/monitor/.ssh/id_ed25519
debug1: Will attempt key: /home/monitor/.ssh/id_ed25519_sk
debug1: Will attempt key: /home/monitor/.ssh/id_xmss
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,sk-ssh-ed25519@openssh.com,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256@openssh.com,webauthn-sk-ecdsa-sha2-nistp256@openssh.com>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 53
debug3: input_userauth_banner: entering
You have logged onto a secured server..All accesses logged
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/monitor/.ssh/id_rsa
debug3: no such identity: /home/monitor/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/monitor/.ssh/id_ecdsa
debug3: no such identity: /home/monitor/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/monitor/.ssh/id_ecdsa_sk
debug3: no such identity: /home/monitor/.ssh/id_ecdsa_sk: No such file or directory
debug1: Trying private key: /home/monitor/.ssh/id_ed25519
debug3: no such identity: /home/monitor/.ssh/id_ed25519: No such file or directory
debug1: Trying private key: /home/monitor/.ssh/id_ed25519_sk
debug3: no such identity: /home/monitor/.ssh/id_ed25519_sk: No such file or directory
debug1: Trying private key: /home/monitor/.ssh/id_xmss
debug3: no such identity: /home/monitor/.ssh/id_xmss: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
monitor@10.188.43.140's password:
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
Permission denied, please try again.
monitor@10.188.43.140's password:
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
Permission denied, please try again.
monitor@10.188.43.140's password:
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
monitor@10.188.43.140: Permission denied (publickey,password).
里面比较关键的一句：
debug1: Skipping ssh-dss key /home/monitor/.ssh/id_dsa - corresponding algo not in PubkeyAcceptedAlgorithms
这里面跳过了找id_dsa这个私钥，而是遍历了PubkeyAcceptedAlgorithms这里面的提到的私钥名字（id_rsa、id_ecdsa、id_ecdsa_sk等等）
顺着这句话接着去Google，原来是OpenSSL7.0以上禁用了dsa，除非在.ssh/config中配置。
我又去看了这台服务器的OpenSSL版本
yum list installed openssl
Loaded plugins: fastestmirror, versionlock
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
Determining fastest mirrors
Installed Packages
openssh.x86_64 8.8p1-1.el7.bclinux @sshupdate
果然，这个版本是8.8的。