Difference between revisions of "User talk:Haoqili"

Revision as of 11:26, 30 June 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".

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, so it can only be used as the last line.

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

Python

• 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:

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