How big of a system do I need to run Squid?

There are no hard-and-fast rules. The most important resource for Squid is physical memory, so put as much in your Squid box as you can. Your processor does not need to be ultra-fast. We recommend buying whatever is economical at the time.

Your disk system will be the major bottleneck, so fast disks are important for high-volume caches. SCSI disks generally perform better than ATA, if you can afford them. Serial ATA (SATA) performs somewhere between the two. Your system disk, and logfile disk can probably be IDE without losing any cache performance.

The ratio of memory-to-disk can be important. We recommend that you have at least 32 MB of RAM for each GB of disk space that you plan to use for caching.

How do I install Squid?

From Binary Packages if available for your operating system.

Or from Source Code.

After SquidFaq/CompilingSquid, you can install it with this simple command:

% make install

If you have enabled ICMP or the pinger then you will also want to type

% su
# make install-pinger

After installing, you will want to read SquidFaq/ConfiguringSquid to edit and customize Squid to run the way you want it to.

How do I start Squid?

First you need to check your Squid configuration. The Squid configuration can be found in /usr/local/squid/etc/squid.conf and includes documentation on all directives.

In the Squid distribution there is a small QUICKSTART guide indicating which directives you need to look closer at and why. At a absolute minimum you need to change the http_access configuration to allow access from your clients.

To verify your configuration file you can use the -k parse option

% /usr/local/squid/sbin/squid -k parse

If this outputs any errors then these are syntax errors or other fatal misconfigurations and needs to be corrected before you continue. If it is silent and immediately gives back the command prompt then your squid.conf is syntactically correct and could be understood by Squid.

After you've finished editing the configuration file, you can start Squid for the first time. The procedure depends a little bit on which version you are using.

First, you must create the swap directories. Do this by running Squid with the -z option:

% /usr/local/squid/sbin/squid -z

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If you run Squid as root then you may need to first create /usr/local/squid/var/logs and your cache_dir directories and assign ownership of these to the cache_effective_user configured in your squid.conf

Once the creation of the cache directories completes, you can start Squid and try it out. Probably the best thing to do is run it from your terminal and watch the debugging output. Use this command:

% /usr/local/squid/sbin/squid -NCd1

If everything is working okay, you will see the line:

Ready to serve requests.

If you want to run squid in the background, as a daemon process, just leave off all options:

% /usr/local/squid/sbin/squid

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Depending on which http_port you select you may need to start squid as root (http_port <1024)

How do I start Squid automatically when the system boots?

by hand

Squid has a restart feature built in. This greatly simplifies starting Squid and means that you don't need to use RunCache or inittab. At the minimum, you only need to enter the pathname to the Squid executable. For example:

/usr/local/squid/sbin/squid

Squid will automatically background itself and then spawn a child process. In your syslog messages file, you should see something like this:

Sep 23 23:55:58 kitty squid[14616]: Squid Parent: child process 14617 started

That means that process ID 14563 is the parent process which monitors the child process (pid 14617). The child process is the one that does all of the work. The parent process just waits for the child process to exit. If the child process exits unexpectedly, the parent will automatically start another child process. In that case, syslog shows:

Sep 23 23:56:02 kitty squid[14616]: Squid Parent: child process 14617 exited with status 1
Sep 23 23:56:05 kitty squid[14616]: Squid Parent: child process 14619 started

If there is some problem, and Squid can not start, the parent process will give up after a while. Your syslog will show:

Sep 23 23:56:12 kitty squid[14616]: Exiting due to repeated, frequent failures

When this happens you should check your syslog messages and cache.log file for error messages.

When you look at a process (ps command) listing, you'll see two squid processes:

24353  ??  Ss     0:00.00 /usr/local/squid/bin/squid
24354  ??  R      0:03.39 (squid) (squid)

The first is the parent process, and the child process is the one called "(squid)". Note that if you accidentally kill the parent process, the child process will not notice.

If you want to run Squid from your termainal and prevent it from backgrounding and spawning a child process, use the -N command line option.

/usr/local/squid/bin/squid -N

from inittab

On systems which have an /etc/inittab file (Digital Unix, Solaris, IRIX, HP-UX, Linux), you can add a line like this:

sq:3:respawn:/usr/local/squid/sbin/squid.sh < /dev/null >> /tmp/squid.log 2>&1

We recommend using a squid.sh shell script, but you could instead call Squid directly with the -N option and other options you may require. A sample squid.sh script is shown below:

C=/usr/local/squid
PATH=/usr/bin:$C/bin
TZ=PST8PDT
export PATH TZ

# User to notify on restarts
notify="root"

# Squid command line options
opts=""

cd $C
umask 022
sleep 10
while [ -f /var/run/nosquid ]; do
        sleep 1
done
/usr/bin/tail -20 $C/logs/cache.log \
        | Mail -s "Squid restart on `hostname` at `date`" $notify
exec bin/squid -N $opts

from rc.local

On BSD-ish systems, you will need to start Squid from the "rc" files, usually /etc/rc.local. For example:

if [ -f /usr/local/squid/sbin/squid ]; then
        echo -n ' Squid'
        /usr/local/squid/sbin/squid
fi

from init.d

Squid ships with a init.d type startup script in contrib/squid.rc which works on most init.d type systems. Or you can write your own using any normal init.d script found in your system as template and add the start/stop fragments shown below.

Start:

/usr/local/squid/sbin/squid

Stop:

/usr/local/squid/sbin/squid -k shutdown
n=120
while /usr/local/squid/sbin/squid -k check && [ $n -gt 0 ]; do
    sleep 1
    echo -n .
    n=`expr $n - 1`
done

with daemontools

Create squid service directory, and the log directory (if it does not exist yet).

mkdir -p /usr/local/squid/supervise/log /var/log/squid
chown squid /var/log/squid

Then, change to the service directory,

cd /usr/local/squid/supervise

and create 2 executable scripts: run

rm -f /var/run/squid/squid.pid
exec /usr/local/squid/sbin/squid -N 2>&1

and log/run.

exec /usr/local/bin/multilog t /var/log/squid

Finally, start the squid service by linking it into svscan monitored area.

cd /service
ln -s /usr/local/squid/supervise squid

Squid should start within 5 seconds.

How do I tell if Squid is running?

You can use the squidclient program:

% squidclient http://www.netscape.com/ > test

There are other command-line HTTP client programs available as well. Two that you may find useful are wget and echoping.

Another way is to use Squid itself to see if it can signal a running Squid process:

% squid -k check

And then check the shell's exit status variable.

Also, check the log files, most importantly the access.log and cache.log files.

squid command line options

These are the command line options for Squid-2:

-a Specify an alternate port number for incoming HTTP requests. Useful for testing a configuration file on a non-standard port.

-d Debugging level for "stderr" messages. If you use this option, then debugging messages up to the specified level will also be written to stderr.

-f Specify an alternate squid.conf file instead of the pathname compiled into the executable.

-h Prints the usage and help message.

-k reconfigure Sends a HUP signal, which causes Squid to re-read its configuration files.

-k rotate Sends an USR1 signal, which causes Squid to rotate its log files. Note, if logfile_rotate is set to zero, Squid still closes and re-opens all log files.

-k shutdown Sends a TERM signal, which causes Squid to wait briefly for current connections to finish and then exit. The amount of time to wait is specified with shutdown_lifetime.

-k interrupt Sends an INT signal, which causes Squid to shutdown immediately, without waiting for current connections.

-k kill Sends a KILL signal, which causes the Squid process to exit immediately, without closing any connections or log files. Use this only as a last resort.

-k debug Sends an USR2 signal, which causes Squid to generate full debugging messages until the next USR2 signal is recieved. Obviously very useful for debugging problems.

-k check Sends a "ZERO" signal to the Squid process. This simply checks whether or not the process is actually running.

-s Send debugging (level 0 only) message to syslog.

-u Specify an alternate port number for ICP messages. Useful for testing a configuration file on a non-standard port.

-v Prints the Squid version.

-z Creates disk swap directories. You must use this option when installing Squid for the first time, or when you add or modify the cache_dir configuration.

-D Do not make initial DNS tests. Normally, Squid looks up some well-known DNS hostnames to ensure that your DNS name resolution service is working properly. (!) obsolete in 3.1 and later.

-F If the swap.state logs are clean, then the cache is rebuilt in the "foreground" before any requests are served. This will decrease the time required to rebuild the cache, but HTTP requests will not be satisfied during this time.

-N Do not automatically become a background daemon process.

-R Do not set the SO_REUSEADDR option on sockets.

-X Enable full debugging while parsing the config file.

-Y Return ICP_OP_MISS_NOFETCH instead of ICP_OP_MISS while the swap.state file is being read. If your cache has mostly child caches which use ICP, this will allow your cache to rebuild faster.

How do I see how Squid works?

  • Check the cache.log file in your logs directory. It logs interesting things as a part of its normal operation and can be boosted to show all the boring details.

  • Install and use the ../CacheManager.

Can Squid benefit from SMP systems?

Squid is a single process application and can not make use of SMP. If you want to make Squid benefit from a SMP system you will need to run multiple instances of Squid and find a way to distribute your users on the different Squid instances just as if you had multiple Squid boxes.

Having two CPUs is indeed nice for running other CPU intensive tasks on the same server as the proxy, such as if you have a lot of logs and need to run various statistics collections during peak hours.

The authentication and group helpers barely use any CPU and does not benefit much from dual-CPU configuration.

Is it okay to use separate drives for Squid?

Yes. Running Squid on separate drives to that which your OS is running is often a very good idea.

Generally seek time is what you want to optimize for Squid, or more precisely the total amount of seeks/s your system can sustain. This is why it is better to have your cache_dir spread over multiple smaller disks than one huge drive (especially with SCSI).

If your system is very I/O bound, you will want to have both your OS and log directories running on separate drives.

Is it okay to use RAID on Squid?

see Section on RAID


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SquidFaq/InstallingSquid (last edited 2012-10-27 10:00:04 by FrancescoChemolli)