off-box mirror-stream and friends

Matthew Dillon dillon at apollo.backplane.com
Sun Feb 15 21:43:24 PST 2009


:I have what appears to be a 'Catch 22', wherein:
:
:hammer mirror-stream /master <user>@<remote_IP>:/new_slave
:
:returns:
:
:PFS slave /new-slave does not exist.
:Do you want to create a new slave PFS? (yes|no) No terminal for response
:Aborting operation
:validate_mrec_header: short read
:
:'No terminal for response'  .was ass u me ed to be a byproduct of comign 
:in off an Xfce4-terminal (Xorg & Xfce4 are quite happy on 2.3.0, BTW)
:
:Dropped back out to the raw tty0 console and tried it from there.
:
:No joy.

    Definitely a bug in the hammer utility, I'm not sure there is 
    anything I can do about it though because the remote ssh connection
    has no channel to accept a Y or N answer... stdin and stdout are used
    for the protocol stream and I think stderr is output only.

    In anycase, I think what this means is that this feature currently
    only works if the slave is local (non-ssh connection).  So you
    would be able to do it with <remote_master> <local_slave>.

:Command *appear* to succeed if/as/when I *manually* create 'new_slave' 
:in advance with a matching shared_uuid. A local mirror-copy to it 
:suceeds, with new_slave showing the files mirrored.
:
:However, while the -vvv flag gives 5-sec updates, they all show a newer 
:starting point that pfs-status has for the target, and the contents of 
:the slave never change.

    You must access the slave via its softlink to get the latest version
    synced from the master.  If you try to access the slave via a null-mount
    you will be accessing a snapshot of the slave, not the current state of
    the slave.  The null mount locks in the transaction id of the slave.

:By way of contrast, mirror-stream between on-box master and on-box slave 
:  - same command otherwise - works fine.  No chdir needed to see the 
:updates, just a 'View, Reload' in thunar and sputniks.

    You are probably accessing it via the softlink, yes?  The gui is
    probably using an absolute path.  If you were to CD into a sub-directory
    (even through the softlink), you would be accessing a snapshot as-of
    when you did the CD, not the latest synced copy.

:Query: Can the loop that seeks a 'yes' be changed to a 5-second 
:countdown-timer with a message such as:
:
:Creating <new_slave> Hit Ctrl-c to abort
:
:.absent which it JFDI.
:
:Thanks,
:
:Bill Hacker

    That won't work, the target over an ssh link has no tty channel.

    Adding an option to create the slave automatically and passing it to
    the target hammer utility when it is run via the ssh, so it never has
    to ask at all, would work.  If someone would like to do that and submit
    a patch, I don't think it would take more then 20 minutes of
    programming.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>





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