Pass host name/ip to which pssh is currently connecting to the command being executed by pssh?

[Google Code Exporter]

Hi!  Love pssh.  It would be great if I could pass the host name/IP as a 
variable to the command being passed, something to the effect of:

pssh -h pssh_hosts.txt -l root -v -o out -e err "sed -i 
's/foobar.example.com/$PSSH_HOST/g' /etc/apticron/apticron.conf"


Example:

I used pssh recently to install apticron.  apticron runs 'apt-get update' once 
a day and emails a list of packages which have updates to the email address 
specified in its configuration file /etc/apticron/apticron.conf

pssh allowed me to easily set the email address I'd like to apticron to send 
those daily reports (sed -i ...).

However, there is also a value which one also can set in the configuration file 
for the name of the server.  If this value is not set, the server will identify 
itself by 'hostname -f'.  I would prefer pass in the sed command to insert the 
name of the host to which pssh is connecting.  

Your help would be greatly appreciated.

Thanks,

Phil

Original issue reported on code.google.com by [e-mail] on 19 Jan 2012 at 10:34

[Google Code Exporter]

In general, it seems that this information should be available on the host.  
For example, would the following command be suitable?

pssh -h pssh_hosts.txt -l root -v -o out -e err 'sed -i 
"s/foobar.example.com/$(hostname -s)/g" /etc/apticron/apticron.conf'

Or is the output of `hostname -s` different than the name to which pssh is 
connecting?

Original comment by [e-mail] on 19 Jan 2012 at 11:16

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[Google Code Exporter]

We're using EC2, so hostname -s and hostname -f both show the internal IP.  
We'd rather show the external IP or external FQDN.

Original comment by [e-mail] on 19 Jan 2012 at 11:19

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[Google Code Exporter]

That makes sense. So, it turns out that this is a terrifically easy feature to 
add. Would you mind testing the attached patch? If it works, I'll commit it 
right away.

Thanks.

Original comment by [e-mail] on 19 Jan 2012 at 11:25

• Changed state: Started
• Added labels: Type-Enhancement
• Removed labels: Type-Defect

Attachments:

• issue62.patch

[Google Code Exporter]

I made the change, deleted /usr/local/bin/pssh, and re-ran the install command, 
then tried something simple:
pssh -h pssh_hosts.txt -l root -v -o out -e err "echo $PSSH_HOST"

Ran it, and the response was a series of blank lines.

Ran:
pssh -h pssh_hosts.txt -l root -v -o out -e err "set | grep PSSH"

Response was a series of lines, all the same:
BASH_EXECUTION_STRING='set | grep PSSH'

(Which means the PSSH_NODENUM is not being created as an environment variable 
on the connected-to-host either...)

Ran:
pssh -h pssh_hosts.txt -l root -v -o out -e err "set | grep BASH"

Output was the following repeated:
BASH=/bin/bash
BASHOPTS=cmdhist:extquote:force_fignore:hostcomplete:interactive_comments:progco
mp:promptvars:sourcepath
BASH_ALIASES=()
BASH_ARGC=()
BASH_ARGV=()
BASH_CMDS=()
BASH_EXECUTION_STRING='set | grep BASH'
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="4" [1]="1" [2]="5" [3]="1" [4]="release" 
[5]="x86_64-pc-linux-gnu")
BASH_VERSION='4.1.5(1)-release'
BASH=/bin/bash
BASH_ARGC=()
BASH_ARGV=()
BASH_EXECUTION_STRING='set | grep BASH'
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="3" [1]="2" [2]="39" [3]="1" [4]="release" 
[5]="i486-pc-linux-gnu")
BASH_VERSION='3.2.39(1)-release'

(which means that the 'set | grep' command does work)

as does:
pssh -h AllEC2Hosts.txt -l root -v -o out -e err "echo $BASH"

Result, repeated several times:
/bin/bash


(so the 'echo' command also works)

Did you try the same patch on your configuration?  Why would mine fail and your 
succeed?  We use Debian 5 & 6.

Original comment by [e-mail] on 20 Jan 2012 at 2:01

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[Google Code Exporter]

You have a few interesting things going on here.

1) pssh -h pssh_hosts.txt -l root -v -o out -e err "echo $PSSH_HOST"

In this case, the PSSH_HOST environment variable is being evaluated on your 
local machine rather than the remote host. If you change the double quotes to 
single quotes, it will make it evaluate on the remote host.

2) After actually testing this change myself, I noticed that I had omitted an 
important change.  In bin/pssh, the line with "SendEnv" should be changed to 
"'-o', 'SendEnv=PSSH_NODENUM PSSH_HOST']". You can either change this by hand, 
or you can grab commit 6631acf, which contains both of the changes associated 
with this issue. My apologies for not taking the time to test the change 
earlier.

3) I believe that you are also running into a problem with sshd trimming down 
the environment on the remote host. In my sshd_config, I have "AcceptEnv 
PSSH_NODENUM PSSH_HOST", which instructs sshd to allow these variables to pass 
through. I will add a comment about this to the pssh.1 man page.

Thanks for your patience and your thorough report which helped me to track 
these issues down very quickly.

Can you confirm that 

Original comment by [e-mail] on 23 Jan 2012 at 5:04

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[Google Code Exporter]

Sorry, my post cut off at the end.

Can you confirm that the feature works after making the change to bin/ssh, 
updating the sshd_config, and making sure to use single quotes?

Thanks.

Original comment by [e-mail] on 23 Jan 2012 at 5:32

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[Google Code Exporter]

Success!  Using (1) single quotes, (2) git pull, (3) modified sshd_config, I 
was able to echo back $PSSH_HOST.

Thanks!

Original comment by [e-mail] on 23 Jan 2012 at 5:53

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[Google Code Exporter]

Great. I'll mark this as done, and it will end up in the next release of pssh. 
Thanks for your participation and help.

Original comment by [e-mail] on 23 Jan 2012 at 6:36

• Changed state: Verified
• Added labels: ****
• Removed labels: ****