Applied Andrey's and my improvments to FAQ item 4.2, discussed on the main ML.
This commit is contained in:
Warren Young
parent
b50e45ff15
commit
b61add2614
|
|
@ -1,3 +1,9 @@
|
|||
2015-02-17 Warren Young <warren@etr-usa.com>
|
||||
|
||||
* faq-using.xml (faq.using.startup-slow): Applied Andrey Repin's
|
||||
improvements <anrdaemon@yandex.ru>, plus made a few minor ones
|
||||
of my own.
|
||||
|
||||
2015-02-16 Corinna Vinschen <corinna@vinschen.de>
|
||||
|
||||
* setup-files.xml (setup-files): Drop hint to set HOME in Windows
|
||||
|
|
|
|||
|
|
@ -33,63 +33,121 @@ it to other missing DLLs and identify their containing packages, see
|
|||
<question><para>Starting a new terminal window is slow. What's going on?</para></question>
|
||||
<answer>
|
||||
|
||||
<para>There are many possible causes for this. This answer is more a
|
||||
list of things to look into than a set of solutions.</para>
|
||||
<para>There are many possible causes for this.</para>
|
||||
|
||||
<para>If your terminal windows suddenly began starting slowly after a
|
||||
Cygwin upgrade, it may indicate issues in the authentication
|
||||
setup.</para>
|
||||
|
||||
<para>For almost all its lifetime, Cygwin has used Unix-like
|
||||
<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
|
||||
files to mirror the contents of the Windows SAM and AD databases.
|
||||
Although these files can still be used, since Cygwin 1.7.34, new
|
||||
installations now use the SAM/AD databases directly.</para>
|
||||
|
||||
<para>To switch to the new method, move these two files out of the way
|
||||
and restart the Cygwin terminal. That runs Cygwin in its new default
|
||||
mode.</para>
|
||||
|
||||
<para>If you are on a system that isn't using AD domain logins, this
|
||||
makes Cygwin use the native Windows SAM database directly, which may be
|
||||
faster than the old method involving <filename>/etc/passwd</filename>
|
||||
and such. At worst, it will only be a bit slower. (The speed difference
|
||||
you see depends on which benchmark you run.) For the AD case, it can be
|
||||
slower than the old method, since it is trading a local file read for a
|
||||
network request. Version 1.7.35 will reduce the number of AD server
|
||||
requests the DLL makes relative to 1.7.34, with the consequence that you
|
||||
will now have to alter <filename>/etc/nsswitch.conf</filename> in order
|
||||
to change your Cygwin home directory, instead of being able to change it
|
||||
from the AD configuration.</para>
|
||||
|
||||
<para>If you are still experiencing very slow shell startups, there are
|
||||
a number of other things you can look into:</para>
|
||||
|
||||
<orderedlist>
|
||||
<listitem>
|
||||
<para>If your terminal windows suddenly began starting slowly after a
|
||||
Cygwin upgrade, the most likely cause is that you have an outdated
|
||||
authentication setup.</para>
|
||||
|
||||
<para>For almost all its lifetime, Cygwin has used Unix-like
|
||||
<filename>/etc/passwd</filename> and <filename>/etc/group</filename> files
|
||||
to mirror the contents of the Windows SAM and AD databases. Although these
|
||||
files can still be used, since Cygwin 1.7.34, new installations now use the
|
||||
SAM/AD databases directly.</para>
|
||||
|
||||
<para>To switch to the new method, move these two files out of the way and
|
||||
restart the Cygwin terminal. That runs Cygwin in its new default mode. If
|
||||
you are on a system that isn't using AD domain logins, this makes Cygwin
|
||||
use the native Windows SAM database directly, which may be faster than the
|
||||
old method involving <filename>/etc/passwd</filename> and such. At worst,
|
||||
it will only be a bit slower. (Which situation applies depends on the
|
||||
benchmark you run.)</para>
|
||||
|
||||
<para>If you are on an AD system, a hybrid approach you might consider is
|
||||
to re-run <command>mkpasswd</command> and <command>mkgroup</command>, then
|
||||
put the following into <filename>/etc/nsswitch.conf</filename> to make
|
||||
Cygwin treat these files as read-only local caches of your AD database:
|
||||
</para>
|
||||
|
||||
<screen>
|
||||
passwd: files
|
||||
group: files
|
||||
</screen>
|
||||
|
||||
<para>By leaving out the "db" option, we are telling the Cygwin DLL not to
|
||||
even <emphasis>try</emphasis> to do AD lookups. If your AD servers are
|
||||
slow, this local cache will speed things up. The downside is the old stale
|
||||
cache problem: any time the AD databases change, your local cache will go
|
||||
out of date until you update the files manually.</para>
|
||||
<para>One common cause of slow Cygwin Terminal starts is a bad DNS
|
||||
setup. This particularly affects AD clients, but there may be other
|
||||
things in your Cygwin startup that depend on getting fast answers
|
||||
back from a network server.</para>
|
||||
|
||||
<para>Keep in mind that this may affect Cygwin even when the domain
|
||||
controller is on the same machine as Cygwin, or is on a nearby
|
||||
server. A bad DNS server IP can cause long delays while the local
|
||||
TCP/IP stack times out on a connection to a server that simply isn't
|
||||
there, for example.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Another common cause of slow Cygwin Terminal starts is a bad DNS
|
||||
setup. Many things that occur during a Cygwin Terminal startup require
|
||||
fast DNS lookups.</para>
|
||||
<para>Another cause for AD client system is slow DC replies,
|
||||
commonly observed in configurations with remote DC access. The
|
||||
Cygwin DLL queries information about every group you're in to
|
||||
populate the local cache on startup. You may speed up this process a
|
||||
little by caching your own information in local files. Run these
|
||||
commands in a Cygwin terminal with write access to
|
||||
<filename>/etc</filename>:</para>
|
||||
|
||||
<screen>getent passwd $(id -u) > /etc/passwd
|
||||
getent group $(id -G) > /etc/group</screen>
|
||||
|
||||
<para>Also, set <filename>/etc/nsswitch.conf</filename> as
|
||||
follows:</para>
|
||||
|
||||
<screen>passwd: files db
|
||||
group: files db</screen>
|
||||
|
||||
<para>This will limit the need for Cygwin to contact the AD domain
|
||||
controller (DC) while still allowing for additional information to
|
||||
be retrieved from DC, such as when listing remote
|
||||
directories.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Either in addition to the previous item or instead of it, you
|
||||
can run <ulink
|
||||
url="https://cygwin.com/cygwin-ug-net/using-cygserver.html"><command>cygserver</command></ulink>
|
||||
as a local caching service to speed up DC requests.</para>
|
||||
|
||||
<para>Cygwin programs will check with <command>cygserver</command>
|
||||
before trying to query the DC directly.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>A less preferable option is to create a static read-only cache
|
||||
of the authentication data. This is the old-fashioned method of
|
||||
making Cygwin integrate with AD, the only method available in
|
||||
releases before 1.7.34. To do this, run <command>mkpasswd</command>
|
||||
and <command>mkgroup</command>, then put the following into
|
||||
<filename>/etc/nsswitch.conf</filename> to make Cygwin treat these
|
||||
files as the only sources of user and group information:</para>
|
||||
|
||||
<screen>passwd: files
|
||||
group: files</screen>
|
||||
|
||||
<para>By leaving out the <computeroutput>db</computeroutput> option,
|
||||
we are telling the Cygwin DLL not to even try to do AD lookups. If
|
||||
your AD servers are slow, this local cache will speed things up. The
|
||||
downside is that you open yourself up to the <ulink
|
||||
url="http://en.wikipedia.org/wiki/Cache_(computing)">stale cache
|
||||
problem</ulink>: any time the AD databases change, your local cache
|
||||
will go out of date until you update the files manually.</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
|
||||
<para>If none of the above helps, the best troubleshooting method is to run
|
||||
your startup scripts in debug mode. Right-click your Cygwin Terminal icon, go
|
||||
to Properties, and edit the command. It should be something like
|
||||
<command>C:\cygwin\bin\mintty.exe -i /Cygwin-Terminal.ico -</command>.
|
||||
Assuming you are using Bash for your login shell, change it to
|
||||
<command>C:\cygwin64\bin\mintty /bin/bash -lx</command>. That will cause it to
|
||||
write out a line for every command it runs. A slow Cygwin Terminal launch
|
||||
usually means one or more of the many commands Cygwin runs when starting up
|
||||
will take a long time. That will be your clue as to what's going on.</para>
|
||||
<para>If none of the above helps, the best troubleshooting method is to
|
||||
run your startup scripts in debug mode. Right-click your Cygwin Terminal
|
||||
icon, go to Properties, and edit the command. It should be something
|
||||
like <command>C:\cygwin\bin\mintty.exe -i /Cygwin-Terminal.ico
|
||||
-</command>. Assuming you are using Bash for your login shell, change
|
||||
it to <command>C:\cygwin\bin\mintty /bin/bash -lx</command> then try
|
||||
running Cygwin Terminal again. The <option>-x</option> option tells Bash
|
||||
to write every command it runs to the terminal before launching it. If
|
||||
the terminal immediately starts filling with lines of text but then
|
||||
pauses, the line where the output paused is your clue as to what's going
|
||||
on. The Cygwin DLL proper probably isn't the cause of the slowdown in
|
||||
this case, since those delays happen before the first line of text
|
||||
appears in the terminal.</para>
|
||||
|
||||
</answer></qandaentry>
|
||||
|
||||
<qandaentry id="faq.using.slow">
|
||||
|
|
|
|||
Loading…
Reference in New Issue