drush command could not be completed

please do run commands with --debug and post here the results. Also specify your environment (os, php version,..)

@chrisabbato: I recently realized that `drush --verbose --debug` is even more verbose. Perhaps it give some clue :) <- debug implies verbose.

It is surprising that all commands halt after bootstrapping to drupal_site but `drush status` is able to do a full bootstrap and complete execution succesfully. I'm out of ideas here.

Does happen the same with for example `drush cron` or `drush cache clear`?
Do you have any drush extension?

Check this: I can updatecode with drush, it will download updates and install them:

# drush --verbose --debug updatecode
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.023 sec]                                   [bootstrap]
Initialized Drupal 6.13 root directory at /root/drupal [0.034 sec]                                    [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.038 sec]                                      [bootstrap]
Initialized Drupal site default at sites/default [0.116 sec]                                                       [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [0.118 sec]                                   [bootstrap]
PDO support not available. Could not pre-validate database credentials. Assuming success [0.121 sec]              [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.121 sec]                [bootstrap]
Successfully connected to the Drupal database. [0.121 sec]                 [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.132 sec]             [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_login() [0.564 sec]                      [bootstrap]
Found command: updatecode [0.571 sec]                               [bootstrap]
Including /root/bin/drush/commands/pm/updatecode.inc [0.571 sec]                    [bootstrap]
Including version specific file : /root/bin/drush/commands/pm/update_info/drupal_6.inc [0.629 sec]                              [notice]
Refreshing update status information ...                                                                                                                                                                       
Done.                                                                                                                                                                                                          
Update information last refreshed: Thu, 2009-09-17 08:43                                                                                                                                                       

Update status information on all installed and enabled Drupal modules:
 Name                            Installed version  Proposed version  Status                    
 Advanced help                   6.x-1.2            6.x-1.2           Up to date                
 Drupal                          6.13               6.14              SECURITY UPDATE available 
 Content Construction Kit (CCK)  6.x-2.5            6.x-2.5           Up to date                
 Date                            6.x-2.3            6.x-2.4           SECURITY UPDATE available 
 Diff                            6.x-2.1-alpha2     6.x-2.1-alpha2    Up to date                
 Features                        6.x-1.0-beta3      6.x-1.0-beta3     Up to date                
 FileField                       6.x-3.1            6.x-3.1           Up to date                
 SWF Tools                       6.x-2.5            6.x-2.5           Up to date                
 ImageAPI                        6.x-1.6            6.x-1.6           Up to date                
 ImageCache                      6.x-2.0-beta10     6.x-2.0-beta10    Up to date                
 ImageField                      6.x-3.1            6.x-3.1           Up to date                
 Pathauto                        6.x-1.1            6.x-1.1           Up to date                
 Token                           6.x-1.12           6.x-1.12          Up to date                
 Views                           6.x-2.6            6.x-2.6           Up to date                
 Wysiwyg                         6.x-2.0            6.x-2.0           Up to date                

NOTE: A code update for the Drupal core is available. 
Drupal itself can't yet be updated by this tool. Please update Drupal manually.

Including non-version specific file : /root/bin/drush/commands/pm/package_handler/wget.inc [18.792 sec]    [notice]
Including non-version specific file : /root/bin/drush/commands/pm/version_control/svn.inc [18.805 sec]        [notice]
Code updates will be made to the following projects:                                                                                                                                                           
Date [date-6.x-2.4]                                                                                                                                                                                            

Note: Updated modules can potentially break your site. It's not recommended to update production sites without prior testing.
Note: A backup of your package will be stored to backups directory if it is not managed by a supported version control system.
Note: If you have made any modifications to any file that belongs to one of these projects, you will have to migrate those modifications after updating.
Do you really want to continue? (y/n): y
Starting to update Date code ... [46.54 sec]        [notice]
Calling mkdir(/root/drupal/backup, 511)
Calling mkdir(/root/drupal/backup/modules, 511)
Calling mkdir(/root/drupal/backup/modules/20090917084412, 511)
Calling rename(/root/drupal/sites/all/modules/date, /root/drupal/backup/modules/20090917084412/date)
Downloading project date ... [46.541 sec]         [notice]
Executing: wget http://ftp.drupal.org/files/projects/date-6.x-2.4.tar.gz
  --2009-09-17 08:44:12--  http://ftp.drupal.org/files/projects/date-6.x-2.4.tar.gz
  Resolvendo ftp.drupal.org... 64.50.236.52
  Connecting to ftp.drupal.org|64.50.236.52|:80... conectado!
  HTTP requisição enviada, aguardando resposta... 200 OK
  Tamanho: 606282 (592K) [application/x-gzip]
  Saving to: `date-6.x-2.4.tar.gz'

       0K .......... .......... .......... .......... ..........  8% 51,4K 11s
      50K .......... .......... .......... .......... .......... 16%  119K 7s
     100K .......... .......... .......... .......... .......... 25%  253K 5s
     150K .......... .......... .......... .......... .......... 33%  294K 3s
     200K .......... .......... .......... .......... .......... 42%  283K 3s
     250K .......... .......... .......... .......... .......... 50%  344K 2s
     300K .......... .......... .......... .......... .......... 59%  703K 1s
     350K .......... .......... .......... .......... .......... 67%  456K 1s
     400K .......... .......... .......... .......... .......... 76%  670K 1s
     450K .......... .......... .......... .......... .......... 84%  708K 0s
     500K .......... .......... .......... .......... .......... 92%  685K 0s
     550K .......... .......... .......... .......... ..        100%  703K=2,5s

  2009-09-17 08:44:15 (233 KB/s) - `date-6.x-2.4.tar.gz' saved [606282/606282]

Downloading date-6.x-2.4.tar.gz was successful. [49.704 sec]     [notice]
Md5 checksum of date-6.x-2.4.tar.gz verified. [49.708 sec]        [notice]
Executing: gzip -d date-6.x-2.4.tar.gz
Executing: tar -xf date-6.x-2.4.tar -C "/root/drupal/sites/all/modules/"
Calling unlink(date-6.x-2.4.tar)
Project date was updated successfully. Installed version is now 6.x-2.4.
Backups were saved into the directory /root/drupal/backup/modules/20090917084412. [49.83 sec]    [ok]
Cache cleared.
Command dispatch complete [51.259 sec]    [notice]

Curiously, if try the following (which is, dl a new module), it fails:

#drush --verbose --debug dl backup_migrate
Found command: dl [0.023 sec]     [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.024 sec]       [bootstrap]
Initialized Drupal 6.13 root directory at /root/drupal [0.034 sec]              [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.039 sec]               [bootstrap]
Initialized Drupal site default at sites/default [0.118 sec]            [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [0.119 sec]       [bootstrap]
PDO support not available. Could not pre-validate database credentials. Assuming success [0.119 sec]     [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.12 sec] [bootstrap]
Successfully connected to the Drupal database. [0.12 sec]   [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.129 sec]    [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_login() [0.549 sec]   [bootstrap]
Including non-version specific file : /root/bin/drush/commands/pm/package_handler/wget.inc [0.554 sec]     [notice]
Including non-version specific file : /root/bin/drush/commands/pm/version_control/svn.inc [0.555 sec]       [notice]
Drush command could not be completed. [0.556 sec]       [error]

no idea. need more info. i suggest focusing in the dl failure since thats a simpler command.

Globalredirect breaks Drush because it executes drupal_goto() during hook_init()... might that be the cause for you guys too?

I'm having the same issue. I removed all modules from sites/all directory and drush worked. Then I tried to put the modules back in the directory one by one to see if I could find one that caused drush to not work but it's not possible to point to one specific module since different combinations had given different results.
I'm using drush on MAMP and CVS as package-handler.

drush --debug status
Found command: status [0.018 sec]                                    [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.018 sec]   [bootstrap]
Initialized Drupal 6.14 root directory at                               [notice]
/Applications/MAMP/htdocs/cucino [0.027 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.027 sec]   [bootstrap]
Initialized Drupal site default at sites/default [0.041 sec]            [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration()      [bootstrap]
[0.041 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.044    [bootstrap]
sec]
Successfully connected to the Drupal database. [0.044 sec]           [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.05 sec]    [bootstrap]
session_start(): Cannot send session cookie - headers already sent by[warning]
(output started at
/Applications/MAMP/htdocs/drush/includes/drush.inc:439) [0.051 sec]
session_start(): Cannot send session cache limiter - headers already [warning]
sent (output started at
/Applications/MAMP/htdocs/drush/includes/drush.inc:439) [0.051 sec]
Cannot modify header information - headers already sent by (output   [warning]
started at /Applications/MAMP/htdocs/drush/includes/drush.inc:439)
[0.06 sec]
Cannot modify header information - headers already sent by (output   [warning]
started at /Applications/MAMP/htdocs/drush/includes/drush.inc:439)
[0.06 sec]
Cannot modify header information - headers already sent by (output   [warning]
started at /Applications/MAMP/htdocs/drush/includes/drush.inc:439)
[0.06 sec]
Cannot modify header information - headers already sent by (output   [warning]
started at /Applications/MAMP/htdocs/drush/includes/drush.inc:439)
[0.06 sec]
Drush command could not be completed. [0.152 sec]

@dodazzi
If you have a temporary site and are interested to find out which module is terminating the script execution, you could try this:
Open includes/module.inc (of Drupal, not Drush) in an editor, and replace

function module_invoke_all() {
  $args = func_get_args();
  $hook = $args[0];
  unset($args[0]);
  $return = array();
  foreach (module_implements($hook) as $module) {
    $function = $module .'_'. $hook;

with

function module_invoke_all() {
  $args = func_get_args();
  $hook = $args[0];
  unset($args[0]);
  $return = array();
  foreach (module_implements($hook) as $module) {
    // ----- log module name -----
    drush_log($module);
    // ----- log module name -----
    $function = $module .'_'. $hook;

The last module name printed is the one that terminates the script (executes drupal_goto() or the like) somewhere in its hook_init() function.

Lastly, here is the patch for globalredirect.

Thanks for the hint.
Unfortunately I haven't been able to get it working.
I tried to modify module.inc but my drupal installation breaks.
Anyway where should I look for the printed modules, in the command line when running drush --debug status?

aegir@classle-desktop:~/drupal-5.x$ drush --debug update

Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.042 sec] [bootstrap]
Loading drushrc "/var/aegir/drupal-5.x/drushrc.php" into "drupal" [bootstrap]
scope. [0.042 sec]
Initialized Drupal 5.18 root directory at /var/aegir/drupal-5.x [notice]
[0.064 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.069 sec] [bootstrap]
Initialized Drupal site default at sites/default [0.071 sec] [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [bootstrap]
[0.075 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.086 [bootstrap]
sec]
Successfully connected to the Drupal database. [0.086 sec] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.094 sec] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_login() [0.213 sec] [bootstrap]
Command update needs the following modules installed/enabled to run: [error]
update_status. [0.215 sec]
The command 'drush.php update' could not be executed. [0.216 sec] [error]

i am getting this as output. but i have update_status module in my sites directory.. how to proceed ??

aegir@classle-desktop:~/drupal-5.x$ drush --debug update

Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.042 sec] [bootstrap]
Loading drushrc "/var/aegir/drupal-5.x/drushrc.php" into "drupal" [bootstrap]
scope. [0.042 sec]
Initialized Drupal 5.18 root directory at /var/aegir/drupal-5.x [notice]
[0.064 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.069 sec] [bootstrap]
Initialized Drupal site default at sites/default [0.071 sec] [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [bootstrap]
[0.075 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.086 [bootstrap]
sec]
Successfully connected to the Drupal database. [0.086 sec] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.094 sec] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_login() [0.213 sec] [bootstrap]
Command update needs the following modules installed/enabled to run: [error]
update_status. [0.215 sec]
The command 'drush.php update' could not be executed. [0.216 sec] [error]

i am getting this as output. but i have update_status module in my sites directory.. how to proceed ??

@dodazzi
Ah, yes, I should have noted that it breaks the website.

Anyway where should I look for the printed modules, in the command line when running drush --debug status?

Exactly, or any command with --debug option.

I have the same problem as #9.

On my test server I have several test or dev sites running various versions of Drupal (depending on when I last used them). Drush is not working on anything that is 6.12 to 6.14, however it IS working on a 6.9 install.

To make things more confusing, my issue just vanished, and I can't remember any particular reason for it. It couldn't 'dl' any modules or drupal sources, and, without updating drush, it started to work. Maybe I updated php, and that did it (I remember to have added new options as I needed for other reasons, I think it was about XML).

Well, can't help much now, hope it's a good hint.

I have drush installed outside of my drupal install.
There was ALSO a copy of Drush in the modules directory of the site I was trying to use drush....
I get errors when I run the command 'drush'

I removed drush from inside the sites/all/modules of the specific install and it works fine.

edit to end of Commands section....

Hopefully this info helps someone.

Here's another tip for debugging this problem: enable php log file and check your php error log for errors. I got this problem when I downloaded coder module, checking the error log shows "Call to undefined function t() in drupal\sites\all\modules\coder\coder.drush.inc on line 10", which led to this issue: http://drupal.org/node/455722

Thanks webthingee - #17

Drush Extras must be deleted.

I had and old copy of sites/all/modules/drush_extras/ laying around.

Make sure you get rid of it!

It seems people in this thread are having a few different issues. In my case I had two issues. One with the coder module and one due to not having update_status module installed.

1. If you have the "coder" module installed you will get errors about "t()...". Depending on what version you have installed you might need to update it, patch it (http://drupal.org/node/455722), or disable and remove it.

2. If you don't have the Drupal Module Update Status (http://drupal.org/project/update_status) installed you will get a error message from Drush about an "update module" being missing. Make sure update_status is installed and enabled.

I'm also having the same problem as #9,

 drush --debug sm
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.024 sec]                                                                                   [bootstrap]
Initialized Drupal 6.14 root directory at /home/***/public_html [0.032 sec]                                                                            [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.034 sec]                                                                                     [bootstrap]
Initialized Drupal site exactseatcovers.com at sites/*****.com [0.132 sec]                                                                   [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [0.134 sec]                                                                        [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.14 sec]                                                                              [bootstrap]
Successfully connected to the Drupal database. [0.14 sec]                                                                                               [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.148 sec]                                                                                     [bootstrap]
session_start(): Cannot send session cookie - headers already sent by (output started at /home/***/drush/includes/drush.inc:482) [0.149 sec]             [warning]
session_start(): Cannot send session cache limiter - headers already sent (output started at /home/***/drush/includes/drush.inc:482) [0.149 sec]         [warning]
Cannot modify header information - headers already sent by (output started at /home/***/drush/includes/drush.inc:482) [0.155 sec]                        [warning]
Drush command could not be completed. [0.156 sec]                                                                                                            [error]

This actually happens no matter what directory i try to run this command from... It's a live site, so I can't really start tinkering with the file system while it's running...

Any idea would be greatly appreciated. I've tried everything on this page...

I had an issue similar to #9. I tried systematically removing modules from my drupal-contrib modules directory. Found out that my issue was being caused by an older version of Coder module. After I updated to the latest beta version of Coder, the problem disappeared.

I was having the issue of "drush command could not be completed" with any command I ran, as several above had. I decided to update all of my modules manually as that seemed to help some. I also updated my Drush version to HEAD and everything seems to be fine now. I hope that helps others that might be experiencing the same problem.

please reopen if there is a todo.

I got stuck on this same 'drush command could not be completed' message and in my case it was due to securepages module: #472338: Drush Incompatible With Secure Pages Module

I found out that in most cases if you're experiencing a "Cannot modify header information..." error you have to increase the php memory limit.
If you're using MAMP PRO be aware that it's not enough to increase the limit editing the template through MAMP PRO UI but you have to change the php.ini file in /Applications/MAMP/conf/php5/php.ini (apparently when using drush MAMP PRO php.ini isn't used).
http://drupal.org/node/505630#comment-2307142

A different issue is when you can correctly run "drush status" but you can't download, run cron and clear cache. This is probably due to an incompatibility with a module. In my case it was the "coder" module. Following this issue #455722: use of t() in coder.drush.inc line 10 should be replaced with dt() I solved the errors by installing the dev version.

I hope this helps.

This may be useless at this point, but I ran into the same error message today (doing help, as well as update sub commands), and found out that in my case this was caused by a missing pear module (Console_Table). I installed that, and everything works fine.

This problem was solved for me by increasing my memory limit in php.ini.

Thanks jrao (#18) for the tip to look in the log files. I found that the memory limit was being exceeded.

@dodazzy: You rule.

Hello,

In my case, I found out that it has something to do with the fact that there was no site configured to use default. So configuring settings.php for the default site solved this problem.

So as mentioned in #6, this is definitely a possibility.

found incompatibility w/ the mobile_tools module.
error was resolved by manually disabling mobile_tools.
was running rush 6.x-3.3 on core 6.19.

Found command: core-status (commandfile=core) [0.04 sec, 3.46 MB] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.04 sec, 3.48 MB] [bootstrap]
Initialized Drupal 6.19 root directory at /home/webkong/drupal [0.05 sec, 4.28 MB] [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.05 sec, 4.29 MB] [bootstrap]
Initialized Drupal site default at sites/default [0.12 sec, 5.13 MB] [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration() [0.13 sec, 5.14 MB] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.13 sec, 5.14 MB] [bootstrap]
Successfully connected to the Drupal database. [0.13 sec, 5.14 MB] [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.13 sec, 5.48 MB] [bootstrap]
session_start(): Cannot send session cookie - headers already sent by (output started at [warning]
/home/webkong/drush/includes/drush.inc:820) bootstrap.inc:1162 [0.13 sec, 5.57 MB]
session_start(): Cannot send session cache limiter - headers already sent (output started at [warning]
/home/webkong/drush/includes/drush.inc:820) bootstrap.inc:1162 [0.13 sec, 5.58 MB]
Cannot modify header information - headers already sent by (output started at [warning]
/home/webkong/drush/includes/drush.inc:820) mobile_tools.module:414 [0.15 sec, 7.38 MB]
Undefined index: SERVER_NAME uc_store.module:559 [0.15 sec, 7.39 MB] [notice]
Undefined index: q uc_store.module:559 [0.15 sec, 7.39 MB] [notice]
Undefined index: parent browscap.module:85 [0.15 sec, 7.44 MB] [notice]
Cannot modify header information - headers already sent by (output started at [warning]
/home/webkong/drush/includes/drush.inc:820) mobile_tools.module:922 [0.16 sec, 8.24 MB]
Drush command could not be completed. [0.16 sec, 8.25 MB] [error]