Installing PECL/PEAR PHP modules on a RHEL box

The default RHEL 5.2 installation does not come with xdebug as part of any of the php RPMs. A quick look around the Net also provided no real RPM candidates that I could use on this system so I had to fall back to using the package management tools (pecl and pear) provided by php.

PECL's Odyssey
RHEL is a general PITA for me already so I just sigh and get on with it:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
...........................................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
/usr/bin/phpize: /tmp/pear/download/xdebug-2.0.3/build/shtool: /bin/sh: bad interpreter: Permission denied
Cannot find autoconf. Please check your autoconf installation and the $PHP_AUTOCONF
environment variable is set correctly and then rerun this script.

ERROR: `phpize' failed

Yep, loving it already!

Why on earth am I not able to invoke /bin/sh (as can be seen by the '/bin/sh: bad interpreter: Permission denied' error above)? Let's see if root can actually run the shell interpreter:

$ sudo /bin/sh
sh-3.2# exit

OK, everything looks good. Why is it breaking when we're trying to run the interpreter from /tmp/pear/download/xdebug-2.0.3/build/shtool?

Back to basics
Perhaps this has something to do with where we're trying to run it from and the user we're doing the installation as (root) seems to be capable of running the interpreter but not from the shtool script for some reason.

$ ls -ld /tmp/
drwxrwxrwt 17 root root 4096 Jun 18 07:41 /tmp/

Obviously _not_ a permissions issue.

$ grep tmp /etc/fstab
/dev/sda2     /tmp    ext3    defaults,nosuid,nodev,noexec    1 2

Ah, there you are! /tmp is mounted with a 'noexec' flag so that's what's causing the execution to fail when we try to install xdebug via pecl. No problem, I'll just set pecl to use /var/tmp instead ... oh, wait, on RHEL systems /var/tmp is just a symlink to /tmp.

*sigh*

Hand me half a brick
Time to work around the issue. Let's go find those directories pear expects to be somehow related to /tmp or /var/tmp:

$ pear config-show | grep tmp
PEAR Installer download        download_dir     /tmp/pear/download
PEAR Installer temp directory  temp_dir         /var/tmp

I updated these to temporarily point elsewhere:

$ pecl config-show| grep tmp
PEAR Installer download        download_dir     /root/tmp/pear/download
PEAR Installer temp directory  temp_dir         /root/tmp
$ sudo mkdir -p /root/tmp/pear/download

Second verse, same as the first
Let's give that installation another whirl and see where we are:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
.....................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
building in /var/tmp/pear-build-root/xdebug-2.0.3
running: /root/tmp/pear/download/xdebug-2.0.3/configure
checking for egrep... grep -E
checking for a sed that does not truncate output... /bin/sed
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details.
ERROR: `/root/tmp/pear/download/xdebug-2.0.3/configure' failed

A quick look at /root/tmp/pear/download/xdebug-2.0.3/configure shows no obvious reasons why we're failing so out comes the cluebat :

$ sudo strace pecl insstall xdebug 2>&1
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
execve("/usr/bin/pecl", ["pecl", "install", "xdebug"], [/* 16 vars */]) = 0
brk(0)                                  = 0x8c3d000

[... truncated ...]

flock(3, LOCK_UN)                       = 0
close(3)                                = 0
write(1, "ERROR: `/root/tmp/pear/download/"..., 63ERROR: `/root/tmp/pear/download/xdebug-2.0.3/configure' failed
) = 63
stat64("/var/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/var/tmp/pear-build-root/xdebug-2.0.3", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
time(NULL)                              = 1213740767
lstat64("/var", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
readlink("/var/tmp", "/tmp", 4096)      = 4
lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root/xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getdents(3, /* 4 entries */, 4096)      = 80
getdents(3, /* 0 entries */, 4096)      = 0
close(3)                                = 0
stat64("/tmp/pear-build-root/xdebug-2.0.3/config.log", {st_mode=S_IFREG|0644, st_size=4948, ...}) = 0
stat64("/tmp/pear-build-root/xdebug-2.0.3/config.nice", {st_mode=S_IFREG|0755, st_size=93, ...}) = 0
unlink("/tmp/pear-build-root/xdebug-2.0.3/config.log") = 0
unlink("/tmp/pear-build-root/xdebug-2.0.3/config.nice") = 0
rmdir("/tmp/pear-build-root/xdebug-2.0.3") = 0
stat64("/var/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/var/tmp/pear-build-root/install-xdebug-2.0.3", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
time(NULL)                              = 1213740767
lstat64("/var", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/var/tmp", {st_mode=S_IFLNK|0777, st_size=4, ...}) = 0
readlink("/var/tmp", "/tmp", 4096)      = 4
lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/tmp/pear-build-root/install-xdebug-2.0.3", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getdents(3, /* 2 entries */, 4096)      = 32
getdents(3, /* 0 entries */, 4096)      = 0
close(3)                                = 0
rmdir("/tmp/pear-build-root/install-xdebug-2.0.3") = 0
stat64("/tmp/glibctestUP8dWe", 0xbfa97ca0) = -1 ENOENT (No such file or directory)
unlink("/tmp/glibctestUP8dWe")          = -1 ENOENT (No such file or directory)
umask(022)                              = 022
close(2)                                = 0
close(1)                                = 0
close(0)                                = 0
munmap(0xb7fd6000, 4096)                = 0
setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
brk(0xa3ce000)                          = 0xa3ce000
setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
brk(0xa18a000)                          = 0xa18a000
exit_group(0)

After all that pecl (aka pear) still tried to muck with /tmp by trying to run things in /var/tmp/pear-build-root/xdebug-2.0.3.

Fine. Be that way.

$ sudo cd /tmp && rm -fr pear pear-build-root
$ sudo ln -s /root/tmp/pear-build-root .

One more time please Sam:

$ sudo pecl install xdebug
downloading xdebug-2.0.3.tgz ...
Starting to download xdebug-2.0.3.tgz (286,325 bytes)
.....................................................done: 286,325 bytes
66 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20060613
Zend Extension Api No:   220060519
building in /var/tmp/pear-build-root/xdebug-2.0.3
running: /root/tmp/pear/download/xdebug-2.0.3/configure
checking for egrep... grep -E
checking for a sed that does not truncate output... /bin/sed
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes

[... truncated ...]

Build complete.
Don't forget to run 'make test'.

running: make INSTALL_ROOT="/var/tmp/pear-build-root/install-xdebug-2.0.3" install
Installing shared extensions:     /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules/
running: find "/var/tmp/pear-build-root/install-xdebug-2.0.3" -ls
36962402    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3
36962465    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr
36962466    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib
36962467    4 drwxr-xr-x   3 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php
36962468    4 drwxr-xr-x   2 root     root         4096 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules
36962464  608 -rwxr-xr-x   1 root     root       618210 Jun 18 08:20 /var/tmp/pear-build-root/install-xdebug-2.0.3/usr/lib/php/modules/xdebug.so

Build process completed successfully
Installing '/usr/lib/php/modules/xdebug.so'
install ok: channel://pecl.php.net/xdebug-2.0.3
configuration option "php_ini" is not set to php.ini location
You should add "extension=xdebug.so" to php.ini

Smell that? It's sweet success!

No more crawling, it's time to walk!
Let's finish the install off for brevity's sake:

$ sudo echo 'zend_extension="/usr/lib/php/modules/xdebug.so"' > /etc/php.d/xdebug.ini
$ php -i | grep xdebug
/etc/php.d/xdebug.ini,
xdebug
xdebug support => enabled
xdebug.auto_trace => Off => Off
xdebug.collect_includes => On => On
xdebug.collect_params => 0 => 0
xdebug.collect_return => Off => Off
xdebug.collect_vars => Off => Off
xdebug.default_enable => On => On
xdebug.dump.COOKIE => no value => no value
xdebug.dump.ENV => no value => no value
xdebug.dump.FILES => no value => no value
xdebug.dump.GET => no value => no value
xdebug.dump.POST => no value => no value
xdebug.dump.REQUEST => no value => no value
xdebug.dump.SERVER => no value => no value
xdebug.dump.SESSION => no value => no value
xdebug.dump_globals => On => On
xdebug.dump_once => On => On
xdebug.dump_undefined => Off => Off
xdebug.extended_info => On => On
xdebug.idekey => root => no value
xdebug.manual_url => http://www.php.net => http://www.php.net
xdebug.max_nesting_level => 100 => 100
xdebug.profiler_aggregate => Off => Off
xdebug.profiler_append => Off => Off
xdebug.profiler_enable => Off => Off
xdebug.profiler_enable_trigger => Off => Off
xdebug.profiler_output_dir => /tmp => /tmp
xdebug.profiler_output_name => cachegrind.out.%p => cachegrind.out.%p
xdebug.remote_autostart => Off => Off
xdebug.remote_enable => Off => Off
xdebug.remote_handler => dbgp => dbgp
xdebug.remote_host => localhost => localhost
xdebug.remote_log => no value => no value
xdebug.remote_mode => req => req
xdebug.remote_port => 9000 => 9000
xdebug.show_exception_trace => Off => Off
xdebug.show_local_vars => Off => Off
xdebug.show_mem_delta => Off => Off
xdebug.trace_format => 0 => 0
xdebug.trace_options => 0 => 0
xdebug.trace_output_dir => /tmp => /tmp
xdebug.trace_output_name => trace.%c => trace.%c
xdebug.var_display_max_children => 128 => 128
xdebug.var_display_max_data => 512 => 512
xdebug.var_display_max_depth => 3 => 3

I can now delete those temporary directories I created in /root/tmp and get back to twitching in the corner, or ...

Easy alternative - just add remount
Instead of the hoops I jumped through to get the pecl bits to stop addressing /tmp I could simply have remounted the /tmp filesystem to allow execution:

$ sudo mount -o remount,exec /tmp
$ sudo pecl install xdebug
$ sudo mount -o remount,defaults,nosuid,nodev,noexec /tmp

This however would have compromised the security that was put in place to stop the possible malicious execution of bits (especially root kits) in /tmp (or /var/tmp).

You have the power (and the knowledge now) so wield it to your benefit.