Linux Collection of Handy Scripts and One Liners - Volume 1.5 (Feedback Edition)
Following reader feedback please see below for an updated version of Volume 1
Ever wanted / needed HTTPD or another service to run with a raised thread priority?
Well you have a couple of options, add additional lines to the /etc/init.d script to change the nice level by adding additional lines on startup, or if you only need to do this on a temporary basis without restarting the service but need every thread to have a raised priority you can use a bash script
Much cleaner script here again thanks to Matthew Ife.
#!/bin/bash
pgrep httpd | while read pid; do renice -20 $pid; done
You can renice between -20 and +20, depending on your requirements you can use this script in a cron job to raise/lower priorities, change httpd for whatever service you want to change the thread priority for.
Ever needed to check files were being accessed / written to?
For this one you’re going to need the inotify-tools package, specifically the inotifywait binary.
inotifywait -m --timefmt "[%a %b %d %H:%M:%S %Y]" --format "%T [%e] %f" -r /folder/to/watch
An example usage is to ensure that caching is working correctly and that cache files are being used in place of processing PHP files, simply change “/folder/to/watch” to be your cache folder, and refresh a few pages.
All being well you’ll get an output similar to the following:
y-tools-3.14)
(root@132 BUZZ1) # /usr/local/bin/inotifywait -m --timefmt "[%a %b %d %H:%M:%S %Y]" --format "%T [%e] %f" -r /path/to/saiweb/wp-content/cache/supercache/*
Setting up watches. Beware: since -r was given, this may take a while!
Watches established.
[Thu Jul 15 20:59:37 2010] [OPEN] index.html
[Thu Jul 15 20:59:37 2010] [CLOSE_NOWRITE,CLOSE] index.html
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] security
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] vsftpd-chrooting-without-the-headache-allowing-shared-directories
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] vsftpd-chrooting-without-the-headache-allowing-shared-directories
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] the-zen-of-secured-shared-hosting-part-1
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] the-zen-of-secured-shared-hosting-part-1
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] php-security-considerations
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] php-security-considerations
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] antivirus-xp-2008-removal
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] antivirus-xp-2008-removal
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] suphplookupexception
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] suphplookupexception
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR] honeypotting-for-viruses-statement-of-fees-200809
[Thu Jul 15 21:00:08 2010] [OPEN,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] honeypotting-for-viruses-statement-of-fees-200809
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR] security
[Thu Jul 15 21:00:08 2010] [CLOSE_NOWRITE,CLOSE,ISDIR]
Alternatively you can use the following approach contributed by Matthew Ife:
auditctl -w /some/path -p w
This will persist for the duration of your ssh session and relevant log entries will appear in /var/log/audit/audit.log, admittedly with far more useful information than inotifywait, and does not require you to install additional packages.
As can be seen the re-write rules are redirecting users to the cached files/folders, in the example above I have used my wp-supercache folder.
Ever needed to quickly get the memory usage of all threads for a service?
You have two options for this a single line
ps -Ao rsz,comm,pid | grep <process name>
or a bash function you can place in your ~/.bashrc
function appmem(){
if [ -z "$1" ]; then
echo "appmem <string to filter>"
echo "i.e. appmem httpd";
else
ps -Ao rsz,comm,pid | grep $1
fi
}
You can then call this (after logging back in again to load the .bashrc up) using
appmem <filter>
replacing
8032 httpd 6207
33080 httpd 13828
8552 httpd 14095
28952 httpd 14102
8540 httpd 14103
30848 httpd 16741
31296 httpd 16832
30452 httpd 18439
31044 httpd 19996
30968 httpd 23287
30356 httpd 23300
25636 httpd 24553
29712 httpd 24771
25588 httpd 24777
31632 httpd 24778
25608 httpd 24796
29716 httpd 24812
28152 httpd 24813
31684 httpd 31291
This shows memory in kilobytes, command, process id, you can see here I currently have 3mb/pid for each httpd process (due to my optimizations, I highly recommend you read parts 1-3)
Dump mysql data and compress on the fly
mysqldump -h <host> -u <user> -p <dbname> | bzip2 -c7 > /path/to/dump.sql.bz2
Self explanatory that one, pipes the output from mysqldump through bzip2 (which has better compression over gzip) and dumps it out to a file, if you realy need a gziped file just replace bzip2 with gzip in the line above.
Ever needed a selection of passwords generated?
Using a slightly modified line originally provided by Matthew Ife,
function pwgen(){
dd if=/dev/urandom bs=2048 count=1 | tr -cd ‘a-zA-Z0-9+@\!\$\(\)’ | cut -b1-15
}
Plant this in your ~/.basrc for a callable function that will generate a selection of 10 secure passwords, handy when you’re fed up of 1337’ifying everything
example output:
)S9esjccl?MMiC1
If you want runtime variable length you could change to cut -1-$1 and then call pwgen 15 for example.
Check mySQL myISAM fragmentation
use information_schema;
SELECT CONCAT(TABLE_SCHEMA,'.',TABLE_NAME) AS TABLE_NAME, ENGINE, (DATA_LENGTH/1024/1024) AS DATA_LENGTH, (INDEX_LENGTH/1024/1024) AS INDEX_LENGTH, ((DATA_LENGTH + INDEX_LENGTH)/1024/1204) AS TOTAL_LENGTH,TABLE_ROWS, UPDATE_TIME, ((INDEX_LENGTH/(DATA_LENGTH + INDEX_LENGTH))*100) AS INDEX_PER,((DATA_LENGTH/(DATA_LENGTH + INDEX_LENGTH))*100) AS DATA_PER, (DATA_FREE/DATA_LENGTH) AS FRAG_RATIO FROM TABLES WHERE ENGINE IS NOT NULL AND DATA_LENGTH >=(1024*1024) AND (DATA_FREE/DATA_LENGTH) >=0.02 ORDER BY FRAG_RATIO DESC;
Gives you a very quick overview of make up of your myISAM tables and their fragmentation (Data free vs data length).
