su - become superuser or another user
su [-] [username [arg...]]
The su command allows one to become another user without logging off or to assume a role. The default user name is root (superuser).
To use su, the appropriate password must be supplied (unless the invoker is already root). If the password is correct, su creates a new shell process that has the real and effective user ID, group IDs, and supplementary group list set to those of the specified username. Additionally, the new shell's project ID is set to the default project ID of the specified user. See getdefaultproj(3PROJECT), setproject(3PROJECT). The new shell will be the shell specified in the shell field of username's password file entry (see passwd(4)). If no shell is specified, /usr/bin/sh is used (see sh(1)). If superuser privilege is requested and the shell for the superuser cannot be invoked using exec(2), /sbin/sh is used as a fallback. To return to normal user ID privileges, type an EOF character (CTRL-D) to exit the new shell.
Any additional arguments given on the command line are passed to the new shell. When using programs such as sh, an arg of the form -c string executes string using the shell and an arg of -r gives the user a restricted shell.
To create a login environment, the command "su -" does the following:
If the first argument to su is a dash (-), the environment will be changed to what would be expected if the user actually logged in as the specified user. Otherwise, the environment is passed along, with the exception of $PATH, which is controlled by PATH and SUPATH in /etc/default/su.
All attempts to become another user using su are logged in the log file /var/adm/sulog (see sulog(4)).
su uses pam(3PAM) with the service name su for authentication, account management, and credential establishment.
Example 1 Becoming User bin While Retaining Your Previously Exported Environment
To become user bin while retaining your previously exported environment, execute:
example% su bin
Example 2 Becoming User bin and Changing to bin's Login Environment
To become user bin but change the environment to what would be expected if bin had originally logged in, execute:
example% su - bin
Example 3 Executing command with user bin's Environment and Permissions
To execute command with the temporary environment and permissions of user bin, type:
example% su - bin -c "command args"
Variables with LD_ prefix are removed for security reasons. Thus, su bin will not retain previously exported variables with LD_ prefix while becoming user bin.
If any of the LC_* variables ( LC_CTYPE, LC_MESSAGES, LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY) (see environ(5)) are not set in the environment, the operational behavior of su for each corresponding locale category is determined by the value of the LANG environment variable. If LC_ALL is set, its contents are used to override both the LANG and the other LC_* variables. If none of the above variables are set in the environment, the "C" (U.S. style) locale determines how su behaves.
See attributes(5) for descriptions of the following attributes:
csh(1), env(1), ksh(1), login(1), roles(1), sh(1), syslogd(1M), exec(2), getdefaultproj(3PROJECT), setproject(3PROJECT), pam(3PAM), pam_authenticate(3PAM), pam_acct_mgmt(3PAM), pam_setcred(3PAM), pam.conf(4), passwd(4), profile(4), sulog(4), syslog(3C), attributes(5), environ(5)
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Created 1996-2020 by Maxim Chirkov
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