The most common problem is that id_dsa.pub key is exactly 1 line starting with ssh-dss and ending with = optionally follopwed by a comment such as the hostname and user. Pasting an ssh key will almost always fail because what you see is seldom what you get. There are dozens of terminal emulators trying to help you with that extra-long line. You may find it broken into 3 or 4 pieces.
So there are two ways to add the key:
1. (most reliable) copy the public key file to the target system as an ASCII file. Then append it to the authorized_keys file:
cp /tmp/id_dsa.pub >> ~userabc/.ssh/authorized_keys
Be sure to count the lines:
wc ~userabc/.ssh/authorized_keys
Each key in the file must be exactly 1 line.
2. Resaerch your terminal emulator (SecureCRT, PuTTY, Reflection, xterm, hyperterminal, etc) to see how the emulator handles copy/paste. Most emulators silently insert end-of-line codes when you copy multiple lines on the screen. Some emulators such as Reflection have an option to suppress the separators and match the original input string.
When you use vi, depending on your .exrc file (or built-in defaults), there may be a wrap-margin setting and/or auto-indent which will break up the line. Turn off wm and ai with:
:set noai wm=0
Then insert the new line. Type ESC to finish the insert and then jump to the beginning of the key using the character 0 (zero). If it moves to the beginning of the line but not the beginning of the key, then the key has been split by copy/paste. Move to the beginning of the line and type J (capital J) which joins the current line with the next line. Move to the space between the two strings. Delete the space (carefully). Repeat the J command and remove the extra space until the key is one line with no imbedded spaces.
(choose your method)
Note also that permissions and ownerships are critical. On the target system, the HOME directory cannot be writable by any user except the owner. .ssh must be 700 permission, all files in .ssh should be 600. If any of these are not correct or the public key is not pasted correctly, sftp (ssh) will fail without telling you what you did wrong.
Bill Hassell, sysadmin
