Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have this id_rsa in my ~/.ssh folder. But it just doesn't authenticate. If I copy it and rename it to anything not id_rsa, it works.

[qfan@mycomputer .ssh]$ ls -al id_rsa id_rsa_good
-rw------- 1 qfan qfan 1766 Dec  3 18:35 id_rsa
-rw------- 1 qfan qfan 1766 Nov 20 19:43 id_rsa_good
[qfan@mycomputer .ssh]$ sha1sum id_rsa id_rsa_good
8cc7f68170038b184bba0541be7d105bb36f7d11  id_rsa
8cc7f68170038b184bba0541be7d105bb36f7d11  id_rsa_good
[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa
qfan@localhost's password: 

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa_good
Enter passphrase for key 'id_rsa_good': 
Last login: Tue Dec  3 18:46:46 2013 from
[qfan@mycomputer ~]$ exit
Connection to localhost closed.

Note that "ssh localhost -i id_rsa" fails and ssh starts to ask for regular password login.

I used -vvv and here's the diff of the logs:

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa_good -vvv 2> log1_good.txt
Enter passphrase for key 'id_rsa_good': 

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa -vvv 2> log2_bad.txt
qfan@localhost's password: 

[qfan@mycomputer .ssh]$ diff log1_good.txt log2_bad.txt 
< debug3: Not a RSA1 key file id_rsa_good.
> debug3: Not a RSA1 key file id_rsa.
< debug1: identity file id_rsa_good type -1
> debug1: identity file id_rsa type 1
< debug2: dh_gen_key: priv key bits set: 126/256
< debug2: bits set: 533/1024
> debug2: dh_gen_key: priv key bits set: 127/256
> debug2: bits set: 503/1024
< debug2: bits set: 506/1024
> debug2: bits set: 539/1024
< debug2: key: id_rsa_good ((nil))
> debug2: key: id_rsa (0x7f953ea96f90)
< debug1: Trying private key: id_rsa_good
< debug1: PEM_read_PrivateKey failed
< debug1: read PEM private key done: type <unknown>
> debug1: Offering public key: id_rsa
> debug3: send_pubkey_test
> debug2: we sent a publickey packet, wait for reply
> debug3: Wrote 368 bytes for a total of 1477
> debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
> 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
[qfan@mycomputer .ssh]$ 

I also tried removing the passphrase from the key file, but it still doesn't work if named id_rsa.

So, what went wrong there?


[qfan@mycomputer .ssh]$ file id_rsa
id_rsa: ASCII text
[qfan@mycomputer .ssh]$ cat id_rsa |head -n2
Proc-Type: 4,ENCRYPTED
share|improve this question
Are you sure the file contains an RSA key? It kind of looks like when it is named id_rsa ssh assumes it is an rsa key (type 1), but when you name it id_rsa_good it isn't sure (type -1). – mfarver Dec 3 '13 at 20:23
Can you run file id_rsa and let us see the output? If it isn't something very much like id_rsa: PEM RSA private key, mfarver may well have a point! – MadHatter Dec 3 '13 at 20:42
It's text file: [qfan@mycomputer .ssh]$ file id_rsa id_rsa: ASCII text [qfan@mycomputer .ssh]$ cat id_rsa |head -n2 -----BEGIN RSA PRIVATE KEY----- Proc-Type: 4,ENCRYPTED – Qi Fan Dec 3 '13 at 21:17
up vote 8 down vote accepted

OK... Found the reason. The in the same .ssh folder is a public key that belongs to a different identity file. When doesn't match id_rsa, it fails automatically. Removing or moving the file makes id_rsa work.

share|improve this answer
I would love to understand why this is so... – David Resnick Mar 6 at 11:54

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.