24 December 2013

Slow SSH login SSH2_MSG_SERVICE_ACCEPT received

After installing new VM, my login to the server was with delay after entering the username.

The ssh -v logs shows as follow:

# ssh -v root@newserver 
...
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received

debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
...

and delay were happening at SSH2_MSG_SERVICE_ACCEPT received debug line,


This server being recently installed, it even couldn't resolve its own hostname:

# ping newserver.example.com
^C
#


So for me I needed to add the new VM FQDN to dns server or to /etc/hosts file of the server:

# vim /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
10.18.20.32 newserver.example.com newserver

And issue resolved. 


Even though disabling useDNS in sshd config file was solved the issue only from Linux client to new server and I still had delay in login from Windows PuTTY.

# cat /etc/ssh/sshd_config |grep -i dns
UseDNS no





8 December 2013

yum update [Errno -3] Error performing checksum

Recently I had this issue of checksum error while doing yum update in my RHEL5 servers.


# yum update
Loaded plugins: security
rhel5-local/primary_db                                                                                                                          |    0 B     00:00
ftp://10.8.227.50/pub/LocalYumRepoRHEL5.1/repodata/c7408a1fce29f12df452017556509b3a3ebde95d7d01e8ea0adb052f97c43e86-primary.sqlite.bz2: [Errno -3] Error performing checksum
Trying other mirror.
Error: failure: repodata/c7408a1fce29f12df452017556509b3a3ebde95d7d01e8ea0adb052f97c43e86-primary.sqlite.bz2 from rhel5-local: [Errno 256] No more mirrors to try.


The usaual following way didn't work for me:

# yum clean all
# yum clean metadata
# yum update


Further I have disabled fastmirror for my yum config and it didn't work as well:

# grep enabled /etc/yum/pluginconf.d/fastestmirror.conf
enabled=0


I've even disabled http cache in yum.conf but same error:

# cat /etc/yum.conf |grep http_caching
http_caching=none


Rebuilding rpm database also was not not helpful:

# rm -rf /var/lib/rpm/__db*
# rpm --rebuilddb
# yum update



But here was my situation, I've created local yum repository for RHEL 5 on my RHEL 6 server!

When reading the createrepo manual, we can see:

# man createrepo
...
 -s --checksum
              Choose the checksum type used in repomd.xml and for packages in the metadata.  The default is now "sha256" (if python has hashlib).  The
              older  default  was  "sha", which is actually "sha1", however explicitly using "sha1" doesn’t work on older (3.0.x) versions of yum, you
              need to specify "sha".
...


Which was exactly my problem. while creating repositoy for RHEL 5 servers in RHEL 6 server, createrepo command used new hash of SHA256, and it's not comaptible with yum of RHEL 5 and before:

Solution:
To use createrepo with "-s sha" option in the repo server:

# createrepo -d -s sha /var/ftp/pub/LocalYumRepoRHEL5.1/


and in the client side:

# yum clean all
# yum clean metadata
# yum update

and there issue settled.