Difference between revisions of "User talk:Haoqili"

Revision as of 13:58, 3 July 2009

Kerberos Bugs I've encountered and fixed (started loggin since Jun 24th).

• When trying to kinit username

ERROR: kinit: Cannot contact any KDC for realm [your realm fqdn] while getting initial credentials

SOLUTION: make sure KDC is running. /usr/local/sbin/krb5kdc

SOLUTION: 1. check log file. I looked in /var/log/auth.log. The bottom of it says: Cannot create reply cache file /var/tmp/krb5kdc_rcache: File exits. 2. sudo rm /var/tmp/krb5kdc_rcache.

• Can't start krb5kdc and in auth.log it says:

ERROR: Address already in use - Cannot bind server socket to port [#] address [IP address]

SOLUTION: 1. see if it is true that port [#] is in use by netstat -nap | grep [#] (I also did pgrep -x krb5kdc). 2. kill the process: pkill -x krb5kdc. note the "-x" is for matching exactly the process "krb5kdc".

• When changing password 'kpasswd', Cannot contact any KDC for realm [your realm fqdn]
• and/or Can't start kadmind (know because echo $? = 1). The last chunk of auth.log says:

ERROR:

kadmind[6924]: No dictionary file specified, continuing without one.

kadmind[6924]: setting up network...

kadmind[6924]: Permission denied - Cannot bind server socket to port 464 address 0.0.0.0

kadmind[6924]: setsockopt(6,IPV6_V6ONLY,1) worked

kadmind[6924]: Permission denied - Cannot bind server socket to port 464 address ::

kadmind[6924]: skipping unrecognized local address family 17

kadmind[6924]: skipping unrecognized local address family 17

kadmind[6924]: Permission denied - Cannot bind server socket to port 464 address 192.168.165.145

kadmind[6924]: setsockopt(6,IPV6_V6ONLY,1) worked

kadmind[6924]: Permission denied - Cannot bind TCP server socket on ::.464

kadmind[6924]: Permission denied - Cannot bind RPC server socket on 0.0.0.0.749

kadmind[6924]: set up 0 sockets

kadmind[6924]: no sockets set up?

Reason (provided by tlyu): It is trying to bind to a privileged port. you need to give it a different port number. actually, two different port numbers: one for password changing and one for normal kadmin.

SOLUTION:

In kdc.conf inserted the last two lines here

kdc_ports = 8888

kpasswd_port = 8887

kadmind_port = 8886

In krb5.conf modify/insert the lines:

admin_server = yourComputerName.domain:8886

kpasswd_server = yourComputerName.domain:8887

• Purge key (kdb5_util purge_mkeys) gives an error

ERROR:

kdb5_util: Invalid argument while updating actkvno data for master principal entry

SOLUTION:

#you must activate the keys that have not been "used" like this:

kdb5_util use_mkey kvno [time]

#i.e. kdb5_util use_mkey 2 'now+2days'

Python Bugs I've encountered and fixed

• When talking to the terminal shell, a command (in my case, kdbt_util add_mkey) asks for password twice (second time is confirmation). I first tried:

p = Popen(command.split(), stdin=PIPE, stdout=PIPE, stderr=PIPE)

(out, err) = p.communicate('password')

(out2, err2) = p.communicate('password')

When I ran it, I got a chunk of error that ends with: ValueError: I/O operation on closed file. So what happens is that communicate closes the pipe, it breaks (even if it only runs once).

Solution code:

p = Popen(command.split(), stdin=PIPE, stdout=PIPE, stderr=PIPE)

p.stdin.write('password'+'\n')

p.stdin.write('password'+'\n')

Note don't forget the new line at the end.

Tips. Useful little things to know

Kerberos

• Good link
• kadmin.local -q 'modprinc +needchange [princname]' , the flag needchange forces the principal to change its password upon kinit.
• kadmin.local -q 'modprinc -policy [policyname] [princname]' Sets up a policy for the principal. This "policy" can store previous passwords and ensures that new passwords are not used before.
• There is a bug in the code 6507 kdb5_util update_princ_encryption uses latest mkey instead of mkey

Shell

• grep vs. egrep

The following characters have special meanings in grep or egrep:

In egrep:

| ^ $ . * + ? ( ) [ { } \

In grep:

^ $ . * \( \) [ \{ \} \

<pre>

'''Python'''<br> Common Stuff

• Cannot do ''[print line for line in linelist]'' must have a function that prints the line, call it, printl(), and do ''[printl(line) for line in linelist]''

More Specific Stuff

• ''p = Popen('blah', stdin=PIPE, stdout=PIPE, stderr=PIPE)''

''(out, err) = p.communicate('inputThing\n')'' <-- don't forget the return "\n" at the end!

• When you're doing a bunch of p=Popen('shell command') be careful because Popen starts a new branch so the next Popen might start without the previous one having completed. To fix this problem, put in:

<pre>

if int(p.wait()) != 0: #meaning that it's not executed

print "error message"

exit

• Two ways to display outputs after Popen( a command that has to get into something, in my case, getting into kadmin.local) 06262009

Way 1:

p = Popen(['commannd', 'all', 'in', 'one', 'line'], stdin=PIPE, stdout=PIPE, stderr=PIPE) #e.g. ['kadmin.local', '-q', 'listprincs']

if int(p.wait()) != 0:

print p.stdout.readlines()

Way 2:

p = Popen(['command', 'front', 'chunk'], stdin=PIPE, stdout=PIPE, stderr=PIPE) #e.g. ['kadmin.local']

(out, err) = p.communicate('rest of command') #e.g. 'listprincs'

print out

• Not type in a chunk of common code every time, i.e.

p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)

This can be changed to:

s = {stdin:PIPE, stdout=PIPE, stderr=PIPE}

p = Popen(cmd, **s)

• For putting in a shell command directly, can turn shell=True. Note the command here can be a single line of string, not split up.

p = Popen(command, shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)

• The p.stdout.readlines() can be read only once