C3 Tips

Say you want to check local directory contents across all the nodes, for example, you can use something like:

cexec ‘ls some_directory’|less .

Use cpush to sync the passwd and shadow files on the nodes. Fairly useful.

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• 200102 : 'cexec' command example: install ntp ( )

Old News ;-)

'cexec' command example: install ntp

[root@blade1 ~]# cexec 'yum -q -y install ntp'

************************* blade *************************
--------- blade1---------
Package ntp-4.2.2p1-9.el5_4.1.x86_64 already installed and latest version
--------- blade2---------
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID 37017186
Importing GPG key 0x37017186 "Red Hat, Inc. (release key) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
--------- blade3---------
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID 37017186
Importing GPG key 0x37017186 "Red Hat, Inc. (release key) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
--------- blade4---------
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID 37017186
Importing GPG key 0x37017186 "Red Hat, Inc. (release key) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
--------- blade5---------
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID 37017186
Importing GPG key 0x37017186 "Red Hat, Inc. (release key) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
--------- blade6---------
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID 37017186
Importing GPG key 0x37017186 "Red Hat, Inc. (release key) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

[root@blade1 ~]# cexec 'chkconfig ntpd on'
************************* blade *************************
--------- blade1---------
--------- blade2---------
--------- blade3---------
--------- blade4---------
--------- blade5---------
--------- blade6---------
[root@blade1 ~]# cexec 'service ntpd start'
************************* blade *************************
--------- blade1---------
Starting ntpd: [ OK ]
--------- blade2---------
Starting ntpd: [ OK ]
--------- blade3---------
Starting ntpd: [ OK ]
--------- blade4---------
Starting ntpd: [ OK ]
--------- blade5---------
Starting ntpd: [ OK ]
--------- blade6---------
Starting ntpd: [ OK ]

Anyway, you get the idea… say you want to check local directory contents across all the nodes, for example, you can use something like:

cexec 'ls some_directory'|less .

I also use cpush to sync the passwd and shadow files on the nodes. Fairly useful.

Let me know if you have questions.

c3-users] virtual clusters / meta clusters.
Thomas Naughton naughtont at ornl.gov
Wed Mar 19 07:47:58 EDT 2014

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Hi Olivier,

The C3 tools were designed to allow for administration of multiple clusters
simultaneously, to include entirely remote systems. I'll have to double
check c3.conf syntax, I'm sure we have paper/documentation on this
somewhere.

So, yes it is most certainly possibleto run commands on all your systems in
one shot. In fact, the 'c3-scale' manual page is documenting this case
where you want to treat a single large cluster as a set of multiple
sub-clusters to increase concurrent execution.

Again, I'll have to check docs for exact syntax, but you can have a
configuration where the only info you have is the cluster headnode and then
issue commands remotely that will use the remote headnode's config file to
identify local cluster nodes.

So you could run the following from your laptop, entirely remote from the 3
clusters, and defer the cluster specs to the headnode of the 3 clusters.
All you'd need locally is the name (or IP) of the 3 cluster head nodes.

cexec cluster1: cluster2: cluster3: hostname

[c3-users] cexce question

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Hi,

Generally when using a pipelined command like this, you'll want to enclose
the entire string in a single quote to avoid having the local shell expand
pieces of the string.   However, when there are problems or complicated
shell escaping the easiest method is to just create a tmp script file and
run that:

      # Print username for my accounts (naughton) on cluster
     tjn at node0:$ cat tmp.sh
     cat /etc/passwd | grep -i naughton | awk -F: '{print $1}'

     tjn at node0:$ cexec :1 bash ./tmp.sh
     ************************* oscar_cluster *************************
     --------- node1---------
     tjn
     naughton
     tjn at node0:$


Note, the "}" in the awk command caused a problem for me when I just tried
this on the cluster from command-line:

   tjn at node0:~$ cexec :1 'cat /etc/passwd | grep -i naughton | awk -F: '{print $1}''
   ************************* oscar_cluster *************************
   --------- node1---------
   awk: line 2: missing } near end of file


I'd have to look more closely to see what's goofing up there, but the
temporary script approach works so I just use that for awk's brackets.

Hope that helps,
--tjn

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