6.6. pam_env - set/unset environment variables
Prev | Chapter 6. A reference guide for available modules | Next

## 6.6. pam_env - set/unset environment variables

`pam_env.so` [ debug ] [ conffile=`conf-file` ] [ envfile=`env-file` ] [ readenv=`0|1` ] [ user_envfile=`env-file` ] [ user_readenv=`0|1` ]

### 6.6.1. DESCRIPTION

The pam_env PAM module allows the (un)setting of environment variables. Supported is the use of previously set environment variables as well as PAM_ITEMs such as PAM_RHOST.

By default rules for (un)setting of variables are taken from the config file `/etc/security/pam_env.conf`. An alternate file can be specified with the conffile option.

Second a file (`/etc/environment` by default) with simple KEY=VAL pairs on separate lines will be read. With the envfile option an alternate file can be specified. And with the readenv option this can be completly disabled.

Third it will read a user configuration file (`$HOME/.pam_environment` by default). The default file file can be changed with the user_envfile option and it can be turned on and off with the user_readenv option.

Since setting of PAM environment variables can have side effects to other modules, this module should be the last one on the stack.

### 6.6.2. DESCRIPTION

The `/etc/security/pam_env.conf` file specifies the environment variables to be set, unset or modified by pam_env(8). When someone logs in, this file is read and the environment variables are set according.

Each line starts with the variable name, there are then two possible options for each variable DEFAULT and OVERRIDE. DEFAULT allows and administrator to set the value of the variable to some default value, if none is supplied then the empty string is assumed. The OVERRIDE option tells pam_env that it should enter in its value (overriding the default value) if there is one to use. OVERRIDE is not used, "" is assumed and no override will be done.

`VARIABLE` [`DEFAULT=[value]`] [`OVERRIDE=[value]`]

(Possibly non-existent) environment variables may be used in values using the ${string} syntax and (possibly non-existent) PAM_ITEMs as well as HOME and SHELL may be used in values using the @{string} syntax. Both the $ and @ characters can be backslash escaped to be used as literal values values can be delimited with "", escaped " not supported. Note that many environment variables that you would like to use may not be set by the time the module is called. For example, ${HOME} is used below several times, but many PAM applications don't make it available by the time you need it. The special variables @{HOME} and @{SHELL} are expanded to the values for the user from his passwd entry.

The "#" character at start of line (no space at front) can be used to mark this line as a comment line.

The `/etc/environment` file specifies the environment variables to be set. The file must consist of simple NAME=VALUE pairs on separate lines. The pam_env(8) module will read the file after the `pam_env.conf` file.

### 6.6.3. OPTIONS

`conffile=`/path/to/pam_env.conf``

  Indicate an alternative `pam_env.conf` style configuration file to override the default. This can be useful when different services need different environments.

`debug`

  A lot of debug information is printed with syslog(3).

`envfile=`/path/to/environment``

  Indicate an alternative `environment` file to override the default. The syntax are simple KEY=VAL pairs on separate lines. The export instruction can be specified for bash compatibility, but will be ignored. This can be useful when different services need different environments.

`readenv=`0|1``

  Turns on or off the reading of the file specified by envfile (0 is off, 1 is on). By default this option is on.

`user_envfile=`filename``

  Indicate an alternative `.pam_environment` file to override the default.The syntax is the same as for /etc/environment. The filename is relative to the user home directory. This can be useful when different services need different environments.

`user_readenv=`0|1``

  Turns on or off the reading of the user specific environment file. 0 is off, 1 is on. By default this option is off as user supplied environment variables in the PAM environment could affect behavior of subsequent modules in the stack without the consent of the system administrator.

### 6.6.4. MODULE TYPES PROVIDED

The `auth` and `session` module types are provided.

### 6.6.5. RETURN VALUES

PAM_ABORT

  Not all relevant data or options could be gotten.

PAM_BUF_ERR

  Memory buffer error.

PAM_IGNORE

  No pam_env.conf and environment file was found.

PAM_SUCCESS

  Environment variables were set.

### 6.6.6. FILES

`/etc/security/pam_env.conf`

  Default configuration file

`/etc/environment`

  Default environment file

`$HOME/.pam_environment`

  User specific environment file

### 6.6.7. EXAMPLES

These are some example lines which might be specified in `/etc/security/pam_env.conf`.

Set the REMOTEHOST variable for any hosts that are remote, default to "localhost" rather than not being set at all

          REMOTEHOST     DEFAULT=localhost OVERRIDE=@{PAM_RHOST}

Set the DISPLAY variable if it seems reasonable

          DISPLAY        DEFAULT=${REMOTEHOST}:0.0 OVERRIDE=${DISPLAY}

Now some simple variables

          PAGER          DEFAULT=less
          MANPAGER       DEFAULT=less
          LESS           DEFAULT="M q e h15 z23 b80"
          NNTPSERVER     DEFAULT=localhost
          PATH           DEFAULT=${HOME}/bin:/usr/local/bin:/bin\
          :/usr/bin:/usr/local/bin/X11:/usr/bin/X11
          XDG_DATA_HOME  @{HOME}/share/

Silly examples of escaped variables, just to show how they work.

          DOLLAR         DEFAULT=\$
          DOLLARDOLLAR   DEFAULT=        OVERRIDE=\$${DOLLAR}
          DOLLARPLUS     DEFAULT=\${REMOTEHOST}${REMOTEHOST}
          ATSIGN         DEFAULT=""      OVERRIDE=\@

### 6.6.8. AUTHOR

pam_env was written by Dave Kinchlea <kinch@kinch.ark.com>.

Prev | Up | Next
6.5. pam_echo - print text messages | Home | 6.7. pam_exec - call an external command