chsh (an abbreviation of "change shell") is acommand onUnix-likeoperating systems that is used to change a loginshell. Users can either supply thepathname of the shell that they wish to change to on the command line, or supply no arguments, in which casechsh allows the user to change the shell interactively.^[1]

chsh is asetuid program that modifies the/etc/passwd file, and only allows ordinary users to modify their own login shells. Thesuperuser can modify the shells of other users, by supplying the name of the user whose shell is to be modified as a command-line argument. For security reasons, the shells that both ordinary users and the superuser can specify are limited by the contents of the/etc/shells file, with the pathname of the shell being required to be exactly as it appears in that file. (This security feature is alterable by re-compiling the source code for the command with a different configuration option, and thus is not necessarily enabled on all systems.) The superuser can, however, also modify the password file directly, setting any user's shell to any executable file on the system without reference to/etc/shells and without usingchsh.^[1][2][3]

On most systems, whenchsh is invoked without the-s command-line option (to specify the name of the shell), it prompts the user to select one. OnMac OS X, if invoked without the-s option,chsh displays a text file in the default editor (initially set to vim) allowing the user to change all of the features of their user account that they are permitted to change, the pathname of the shell being the name next to "Shell:". When the user quits vim, the changes made there are transferred to the /etc/passwd file which only root can change directly.^[2][4]

Using the-s option (for example:%chsh-s/usr/local/bin/bash) greatly simplifies the task of changing shells.

Depending on the system,chsh may or may not prompt the user for a password before changing the shell, or entering interactive mode. On some systems, use ofchsh by non-root users is disabled entirely by the sysadmin.^[4]

On manyLinux distributions, thechsh command is aPAM-aware application. As such, its behaviour can be tailored, using PAM configuration options, for individual users. For example, anauth directive that specifies thepam_listfile.so module can be used to denychsh access to individual users, by specifying a file of the usernames to deny access to with thelistfile= option to that module (along with thesense=deny option).^[5]

POSIX does not describe utilities such aschsh, which are used for modifying the user's entry in/etc/passwd. Most Unix-like systems providechsh.^[6]SVr4-based systems provided a similar capability withpasswd. Two of the three remaining systems (IBM AIX^[7] andHP-UX^[8]) providechsh in addition topasswd -e. The exception isSolaris, where non-administrators are unable to change their shell unless a network name server such asNIS orNIS+ is installed.^[9][10] The obsolete^[11]SGI SVr4 systemIRIX64 also lackedchsh.

• Comparison of command shells

• Cynthia Gibas and Per Jambeck (2001).Developing Bioinformatics Computer Skills. O'Reilly. pp. 89–90.ISBN 1565926641. — some examples of invokingchsh with the-s and-l options

The WikibookGuide to Unix has a page on the topic of:Choosing a shell

• chsh(1) – 4.2BSD General CommandsManual
• chsh(1): change your login shell – Linux User CommandsManual
• chsh(1) – Darwin andmacOS General CommandsManual
• passwd(1) – Solaris 11.4 User Commands ReferenceManual

• Unix user management and support-related utilities
• Standard Unix programs

• Articles with short description
• Short description is different from Wikidata