Pistos's questions

I have a small local network which has a Gentoo box and a Windows box. I mount a share originating on the Windows box onto the Gentoo box with a command like:

mount -t cifs -o username=WindowsUsername,password=thepassword,uid=pistos //192.168.0.103/Users /mnt/windowsbox

Most of the time, everything Just Works, and I can read and write without problems. However, every few weeks or so, the connection or the mount point seems to go dead or hang, such that any process that tries to access the mount point gets stuck in D state (disk, or I/O wait). These processes become impervious to TERM and KILL signals. Disconnecting and reconnecting the Windows box from the network does not help. The frozen state lasts for 5+ minutes. It's really frustrating and gets in the way of normal work, because it freezes Save As dialogues, ls commands, etc. If I issue a umount on the mount point, it either hangs also, or reports that the mount point is in use. Eventually, the dead state resolves itself, and the mount point gets unmounted, or it becomes possible to umount with no delay.

My guess is that this happens when the connection/mount has gone idle, or when the Windows machine has been idle. I am not really sure.

Why is this happening, and what can I do to prevent it? Or how can I successfully kill these D-state processes at will?

Possibly related: CIFS mounts hang on read

I have a PHP site that has many dynamically generated pages. I'm trying to turn to mod_cache to help boost performance, because in most cases, content does not change in a given day.

I have configured mod_cache as best I could, following examples around the web, including the mod_cache page on apache.org. When I set LogLevel debug, I see a bit of information about the caching that is [not] happening. There are plenty of pairs of lines like this:

[Fri Jun 01 17:28:18 2012] [debug] mod_cache.c(141): Adding CACHE_SAVE filter for /foo/bar
[Fri Jun 01 17:28:18 2012] [debug] mod_cache.c(148): Adding CACHE_REMOVE_URL filter for /foo/bar

Which is fine, because I've set CacheEnable disk /foo, to indicate that I want everything under /foo cached. I'm new to mod_cache, but my understanding about these lines is that it just means that mod_cache has acknowledged that the URL is supposed to be cached, but there are supposed to be more lines indicating that it is saving the data to cache, and then later retrieving them on subsequent hits to the same URL.

I can hit the same URL till I'm blue in the face, whether with F5 refreshing, or not, or with different browsers, or different computers. It's always that pair of lines that shows in the logs, and nothing else.

When I set CacheEnable disk /, then I see more activity. But I don't want to cache the entire site, and there are many, many different subpaths to the site, so I don't want to have to modify code to set no-cache headers in all the necessary places.

I'll mention that mod_rewrite is in use here, rewriting /foo/bar to something like index.php?baz=/foo/bar, but my understanding is that mod_cache uses the pre-rewrite URL, not the post-rewrite URL.

As far as I can tell, I have the response headers not getting in the way of caching. Here's an example from one hit:

Cache-Control:must-revalidate, max-age=3600
Connection:Keep-Alive
Content-Encoding:gzip
Content-Length:16790
Content-Type:text/html
Date:Fri, 01 Jun 2012 21:43:09 GMT
Expires:Fri,  1 Jun 2012 18:43:09 -0400
Keep-Alive:timeout=15, max=100
Pragma:
Server:Apache
Vary:Accept-Encoding

mod_cache config is as follows:

CacheRoot   /var/cache/apache2/
CacheDirLevels 3
CacheDirLength 2
CacheEnable disk /foo

What is getting in the way of mod_cache doing its job of caching?

Consider a system with limited memory, like a smallish VPS. Suppose there are a handful of processes that need to stay alive, and one process "P" that would be nice to have around, but is not strictly necessary. What I'd like do is keep P around under times of low activity, but when activity picks up beyond a certain threshold, kill off P until activity lowers again, at which time I want P to come back. I'm not sure yet what I'd like "activity" to mean, but it could be any of: memory usage, swap usage, server load values.

I'm already using Monit, so it would be good if this could be accomplished with Monit. Bear in mind that I don't mean process memory usage, I mean overall system load. I don't have to use Monit for this, though, if something else will do the job.

(I have already read How can I test a new cron script ?.)

I have a specific problem (cron job doesn't appear to run, or run properly), but the issue is general: I'd like to debug scripts that are cronned. I am aware that I can set up a * * * * * crontab line, but that is not a fully satisfactory solution. I would like to be able to run a cron job from the command line as if cron were running it (same user, same environment variables, etc.). Is there a way to do this? Having to wait 60 seconds to test script changes is not practical.

Even though I've used Apache for years, I'm new to https and SSL with Apache. For testing, I have executed some openssl commands as found on the Internet to generate a self-signed cert for use with Apache. When I hit an https://mydomain URL for the first time, I got the browser warning about the cert, which was expected. After accepting the cert in my browser(s), it seems that all https URLs are redirecting to the http equivalents with a 301.

I can't determine why. Any clues? I have one .htaccess file in the root of the public dir, but I don't think it is the cause (there is no mention of https).

This is Gentoo Linux, Apache 2.2.11.

Here is a portion of my Apache config. Most of it is just what came with Gentoo's Apache installation by default.

<IfDefine SSL>
<IfDefine SSL_DEFAULT_VHOST>
<IfModule ssl_module>
    Listen 443
    NameVirtualHost *:443

    <VirtualHost *:443>
        ServerName mydomain.com
        Include /etc/apache2/vhosts.d/default_vhost.include
        ErrorLog /var/log/apache2/mydomain.com.ssl.errors
        CustomLog /var/log/apache2/mydomain.com.ssl.log combined

        <IfModule log_config_module>
        TransferLog /var/log/apache2/ssl_access_log
        </IfModule>

        SSLEngine on

        SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL

        SSLCertificateFile /etc/apache2/ssl/mydomain.com.crt
        SSLCertificateKeyFile /etc/apache2/ssl/mydomain.com.key
        SSLOptions StrictRequire

        <FilesMatch "\.(cgi|shtml|phtml|php)$">
        SSLOptions +StdEnvVars
        </FilesMatch>

        <Directory "/var/www/localhost/cgi-bin">
        SSLOptions +StdEnvVars
        </Directory>

        SSLProtocol all -SSLv2

        <IfModule setenvif_module>
        BrowserMatch ".*MSIE.*" \
            nokeepalive ssl-unclean-shutdown \
            downgrade-1.0 force-response-1.0
        </IfModule>

        <IfModule log_config_module>
        CustomLog /var/log/apache2/ssl_request_log \
            "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
        </IfModule>

        RewriteEngine On

        DocumentRoot "/var/www/mydomain.com/public"
        <Directory "/var/www/mydomain.com/public">
            SSLRequireSSL
            Options Indexes FollowSymLinks ExecCGI
            AllowOverride All
            Order allow,deny
            Allow from all
        </Directory>

    </VirtualHost>

</IfModule>
</IfDefine>
</IfDefine>

Under Linux, how can I find all the files and directories that are writable (or, actually, not writable) by a particular user?

Edit: To clarify, I meant under a particular subdir, not systemwide. And yes, that means all the permutations and combinations of user, group and world writability that would allow that user to write. I know what the question entails semantically, I was hoping for a one- or few-liner to execute to get a list of these files.