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+<H1>Administration Reference</H1>
+<HR><P ALIGN="center"> <A HREF="../index.htm"><IMG SRC="../books.gif" BORDER="0" ALT="[Return to Library]"></A> <A HREF="auarf002.htm#ToC"><IMG SRC="../toc.gif" BORDER="0" ALT="[Contents]"></A> <A HREF="auarf132.htm"><IMG SRC="../prev.gif" BORDER="0" ALT="[Previous Topic]"></A> <A HREF="#Bot_Of_Page"><IMG SRC="../bot.gif" BORDER="0" ALT="[Bottom of Topic]"></A> <A HREF="auarf134.htm"><IMG SRC="../next.gif" BORDER="0" ALT="[Next Topic]"></A> <A HREF="auarf284.htm#HDRINDEX"><IMG SRC="../index.gif" BORDER="0" ALT="[Index]"></A> <P>
+<P>
+<H2><A NAME="HDRFS_CHECKSERVERS" HREF="auarf002.htm#ToC_147">fs checkservers</A></H2>
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+<P><STRONG>Purpose</STRONG>
+<P>Displays the status of server machines
+<P><STRONG>Synopsis</STRONG>
+<PRE><B>fs checkservers</B> [<B>-cell</B> <<VAR>cell to check</VAR>>] [<B>-all</B>] [<B>-fast</B>]
+ [<B>-interval</B> <<VAR>seconds between probes</VAR>>] [<B>-help</B>]
+
+<B>fs checks</B> [<B>-c</B> <<VAR>cell to check</VAR>>] [<B>-a</B>] [<B>-f</B>]
+ [<B>-i</B> <<VAR>seconds between probes</VAR>>] [<B>-h</B>]
+</PRE>
+<P><STRONG>Description</STRONG>
+<P>The <B>fs checkservers</B> command reports whether certain AFS server
+machines are accessible from the local client machine. The machines
+belong to one of two classes, and the Cache Manager maintains a list of them
+in kernel memory:
+<UL>
+<P><LI>The database server machines in every cell listed in the local
+<B>/usr/vice/etc/CellServDB file</B>, plus any machines added to the
+memory list by the <B>fs newcell</B> command since the last reboot.
+<P><LI>All file server machines the Cache Manager has recently contacted, and
+which it probably needs to contact again soon. In most cases, the Cache
+Manager holds a callback on a file or volume fetched from the machine.
+</UL>
+<P>If the Cache Manager is unable to contact the <B>vlserver</B> process
+on a database server machine or the <B>fileserver</B> process on a file
+server machine, it marks the machine as inaccessible. (Actually, if a
+file server machine is multihomed, the Cache Manager attempts to contact all
+of the machine's interfaces, and only marks the machine as down if the
+<B>fileserver</B> fails to reply via any of them.) The Cache
+Manager then periodically (by default, every three minutes) sends a probe to
+each marked machine, to see if it is still inaccessible. If a
+previously inaccessible machine responds, the Cache Manager marks it as
+accessible and no longer sends the periodic probes to it.
+<P>The <B>fs checkservers</B> command updates the list of inaccessible
+machines by having the Cache Manager probe a specified set of them:
+<UL>
+<P><LI>By default, only machines that are marked inaccessible and belong to the
+local cell (the cell listed in the local <B>/usr/vice/etc/ThisCell</B>
+file)
+<P><LI>If the <B>-cell</B> argument is included, only machines that are
+marked inaccessible and belong to the specified cell
+<P><LI>If the <B>-all</B> flag is included, all machines marked inaccessible
+</UL>
+<P>If the <B>-fast</B> flag is included, the Cache Manager does not probe
+any machines, but instead reports the results of the most recent previous
+probe.
+<P>To set the interval between probes rather than produce a list of
+inaccessible machines, use the <B>-interval</B> argument. The
+non-default setting persists until the machine reboots; to preserve it
+across reboots, put the appropriate <B>fs checkservers</B> command in the
+machine's AFS initialization files.
+<P><STRONG>Cautions</STRONG>
+<P>The command can take quite a while to complete, if a number of machines do
+not respond to the Cache Manager's probe. The Cache Manager probes
+machines sequentially and waits a standard timeout period before marking the
+machine as unresponsive, to allow for slow network communication. To
+make the command shell prompt return quickly, put the command in the
+background. It is harmless to interrupt the command by typing
+<B>Ctrl-c</B> or another interrupt signal.
+<P>Note that the Cache Manager probes only server machines marked inaccessible
+in its memory list. A server machine's absence from the output
+does not necessarily mean that it is functioning, because it possibly is not
+included in the memory list at all (if, for example, the Cache Manager has not
+contacted it recently). For the same reason, the output is likely to
+vary on different client machines.
+<P>Unlike most <B>fs</B> commands, the <B>fs checkservers</B> command
+does not refer to the AFSCELL environment variable.
+<P><STRONG>Options</STRONG>
+<DL>
+<P><DT><B>-cell
+</B><DD>Names each cell in which to probe server machines marked as
+inaccessible. Provide the fully qualified domain name, or a shortened
+form that disambiguates it from the other cells listed in the local
+<B>/usr/vice/etc/CellServDB</B> file. Combine this argument with
+the <B>-fast</B> flag if desired, but not with the <B>-all</B>
+flag. Omit both this argument and the <B>-all</B> flag to probe
+machines in the local cell only.
+<P><DT><B>-all
+</B><DD>Probes all machines in the Cache Manager's memory list that are
+marked inaccessible. Combine this argument with the <B>-fast</B>
+flag if desired, but not with the <B>-cell</B> argument. Omit both
+this flag and the <B>-cell</B> argument to probe machines in the local
+cell only.
+<P><DT><B>-fast
+</B><DD>Displays the Cache Manager's current list of machines that are
+inaccessible, rather than sending new probes. The output can as old as
+the current setting of the probe interval (by default three minutes, and
+maximum ten minutes).
+<P><DT><B>-interval
+</B><DD>Sets or reports the number of seconds between the Cache Manager's
+probes to machines in the memory list that are marked inaccessible:
+<UL>
+<P><LI>To set the interval, specify a value from the range between <B>1</B>
+and <B>600</B> (10 minutes); the default is <B>180</B> (three
+minutes). The issuer must be logged in as the local superuser
+<B>root</B>. The altered setting persists until again changed with
+this command, or until the machine reboots, at which time the setting returns
+to the default.
+<P><LI>Provide a value of <B>0</B> (zero) to display the current interval
+setting. No privilege is required. Do not combine this argument
+with any other.
+</UL>
+<P><DT><B>-help
+</B><DD>Prints the online help for this command. All other valid options
+are ignored.
+</DL>
+<P><STRONG>Output</STRONG>
+<P>If there are no machines marked as inaccessible, or if all of them now
+respond to the Cache Manager's probe, the output is:
+<PRE> All servers are running.
+
+</PRE>
+<P>Note that this message does not mean that all server machines in each
+relevant cell are running. The output indicates the status of only
+those machines that the Cache Manager probes.
+<P>If a machine fails to respond to the probe within the timeout period, the
+output begins with the string
+<PRE> These servers unavailable due to network or server problems:
+
+</PRE>
+<P>and lists the hostname of each machine on its own line. The Cache
+Manager stores machine records by Internet address, so the format of each
+hostname (uppercase or lowercase letters, or an Internet address in dotted
+decimal format) depends on how the local cell's name service translates
+it at the time the command is issued. If a server machine is
+multihomed, the output lists only one of its interfaces (usually, the
+currently most preferred one).
+<P>If the <B>-interval</B> argument is provided with a value between
+<B>1</B> and <B>600</B>, there is no output. If the value is
+<B>0</B>, the output reports the probe interval as follows:
+<PRE> The current down server probe interval is <VAR>interval</VAR> secs
+
+</PRE>
+<P><STRONG>Examples</STRONG>
+<P>The following command displays the Cache Manager's current list of
+unresponsive machines in the local cell, rather than probing them
+again. The output indicates that if there were any machines marked
+inaccessible, they all responded to the previous probe.
+<PRE> % <B>fs checkservers -fast</B>
+ All servers are running.
+
+</PRE>
+<P>The following example probes machines in the Cache Manager's memory
+list that belong to the <B>stateu.edu</B> cell:
+<PRE> % <B>fs checkservers -cell stateu.edu</B>
+ All servers are running.
+
+</PRE>
+<P>The following example probes all server machines in the Cache
+Manager's memory list. It reports that two machines did not
+respond to the probe.
+<PRE> % <B>fs checkservers -all</B>
+ These servers unavailable due to network or server problems:
+ fs1.abc.com SV3.STATE.EDU.
+
+</PRE>
+<P><STRONG>Privilege Required</STRONG>
+<P>To set the probe interval, the issuer must be logged in as the local
+superuser <B>root</B>. Otherwise, no privilege is required.
+<P><STRONG>Related Information</STRONG>
+<P><A HREF="auarf019.htm#HDRCLI_CSDB">CellServDB (client version)</A>
+<P><A HREF="auarf032.htm#HDRCLI_THISCELL">ThisCell (client version)</A>
+<P><A HREF="auarf154.htm#HDRFS_NEWCELL">fs newcell</A>
+<P>
+<HR><P ALIGN="center"> <A HREF="../index.htm"><IMG SRC="../books.gif" BORDER="0" ALT="[Return to Library]"></A> <A HREF="auarf002.htm#ToC"><IMG SRC="../toc.gif" BORDER="0" ALT="[Contents]"></A> <A HREF="auarf132.htm"><IMG SRC="../prev.gif" BORDER="0" ALT="[Previous Topic]"></A> <A HREF="#Top_Of_Page"><IMG SRC="../top.gif" BORDER="0" ALT="[Top of Topic]"></A> <A HREF="auarf134.htm"><IMG SRC="../next.gif" BORDER="0" ALT="[Next Topic]"></A> <A HREF="auarf284.htm#HDRINDEX"><IMG SRC="../index.gif" BORDER="0" ALT="[Index]"></A> <P>
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