environment: Add --user.
This change allows overriding the home directory of all filesystem mappings to help hide the identity of the calling user in a container. * doc/guix.texi (Invoking guix environment)[--container]: Mention --user. [--user]: Add item. * guix/scripts/environment.scm (show-help): Add --user. (%options): Add --user. (launch-environment/container) Add 'user' parameter. Update doc. Override 'user-mappings' using 'override-user-mappings'. Consider override for chdir. (mock-passwd, user-override-home, overrid-euser-dir): New procedures. (guix-environment): Disallow --user without --container. Provide user to 'launch-environment/container'. * tests/guix-environment.sh: Add user test. Signed-off-by: Ludovic Courtès <ludo@gnu.org>
This commit is contained in:
Mike Gerwitz
Ludovic Courtès
parent
07ec349229
commit
e37944d827
@ -7286,10 +7286,11 @@ Attempt to build for @var{system}---e.g., @code{i686-linux}.
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@cindex container
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Run @var{command} within an isolated container. The current working
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directory outside the container is mapped inside the container.
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Additionally, a dummy home directory is created that matches the current
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user's home directory, and @file{/etc/passwd} is configured accordingly.
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The spawned process runs as the current user outside the container, but
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has root privileges in the context of the container.
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Additionally, unless overridden with @code{--user}, a dummy home
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directory is created that matches the current user's home directory, and
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@file{/etc/passwd} is configured accordingly. The spawned process runs
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as the current user outside the container, but has root privileges in
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the context of the container.
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@item --network
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@itemx -N
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@ -7313,6 +7314,31 @@ example, the @code{fontconfig} package inspects
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@code{--link-profile} allows these programs to behave as expected within
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the environment.
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@item --user=@var{user}
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@itemx -u @var{user}
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For containers, use the username @var{user} in place of the current
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user. The generated @file{/etc/passwd} entry within the container will
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contain the name @var{user}; the home directory will be
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@file{/home/USER}; and no user GECOS data will be copied. @var{user}
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need not exist on the system.
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Additionally, any shared or exposed path (see @code{--share} and
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@code{--expose} respectively) whose target is within the current user's
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home directory will be remapped relative to @file{/home/USER}; this
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includes the automatic mapping of the current working directory.
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@example
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# will expose paths as /home/foo/wd, /home/foo/test, and /home/foo/target
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cd $HOME/wd
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guix environment --container --user=foo \
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--expose=$HOME/test \
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--expose=/tmp/target=$HOME/target
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@end example
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While this will limit the leaking of user identity through home paths
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and each of the user fields, this is only one useful component of a
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broader privacy/anonymity solution---not one in and of itself.
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@item --expose=@var{source}[=@var{target}]
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For containers, expose the file system @var{source} from the host system
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as the read-only file system @var{target} within the container. If
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@ -163,6 +163,10 @@ COMMAND or an interactive shell in that environment.\n"))
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(display (G_ "
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-P, --link-profile link environment profile to ~/.guix-profile within
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an isolated container"))
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(display (G_ "
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-u, --user=USER instead of copying the name and home of the current
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user into an isolated container, use the name USER
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with home directory /home/USER"))
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(display (G_ "
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--share=SPEC for containers, share writable host file system
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according to SPEC"))
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@ -250,6 +254,10 @@ COMMAND or an interactive shell in that environment.\n"))
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(option '(#\P "link-profile") #f #f
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(lambda (opt name arg result)
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(alist-cons 'link-profile? #t result)))
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(option '(#\u "user") #t #f
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(lambda (opt name arg result)
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(alist-cons 'user arg
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(alist-delete 'user result eq?))))
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(option '("share") #t #f
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(lambda (opt name arg result)
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(alist-cons 'file-system-mapping
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@ -410,43 +418,50 @@ environment variables are cleared before setting the new ones."
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(pid (match (waitpid pid)
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((_ . status) status)))))
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(define* (launch-environment/container #:key command bash user-mappings
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(define* (launch-environment/container #:key command bash user user-mappings
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profile paths link-profile? network?)
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"Run COMMAND within a container that features the software in PROFILE.
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Environment variables are set according to PATHS, a list of native search
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paths. The global shell is BASH, a file name for a GNU Bash binary in the
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store. When NETWORK?, access to the host system network is permitted.
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USER-MAPPINGS, a list of file system mappings, contains the user-specified
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host file systems to mount inside the container. LINK-PROFILE? creates a
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symbolic link from ~/.guix-profile to the environment profile."
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host file systems to mount inside the container. If USER is not #f, each
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target of USER-MAPPINGS will be re-written relative to '/home/USER', and USER
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will be used for the passwd entry. LINK-PROFILE? creates a symbolic link from
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~/.guix-profile to the environment profile."
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(mlet %store-monad ((reqs (inputs->requisites
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(list (direct-store-path bash) profile))))
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(return
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(let* ((cwd (getcwd))
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(passwd (getpwuid (getuid)))
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(home (getenv "HOME"))
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(passwd (mock-passwd (getpwuid (getuid))
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user
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bash))
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(home-dir (passwd:dir passwd))
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;; Bind-mount all requisite store items, user-specified mappings,
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;; /bin/sh, the current working directory, and possibly networking
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;; configuration files within the container.
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(mappings
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(append user-mappings
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;; Current working directory.
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(list (file-system-mapping
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(source cwd)
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(target cwd)
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(writable? #t)))
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;; When in Rome, do as Nix build.cc does: Automagically
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;; map common network configuration files.
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(if network?
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%network-file-mappings
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'())
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;; Mappings for the union closure of all inputs.
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(map (lambda (dir)
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(file-system-mapping
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(source dir)
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(target dir)
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(writable? #f)))
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reqs)))
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(override-user-mappings
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user home
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(append user-mappings
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;; Current working directory.
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(list (file-system-mapping
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(source cwd)
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(target cwd)
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(writable? #t)))
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;; When in Rome, do as Nix build.cc does: Automagically
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;; map common network configuration files.
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(if network?
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%network-file-mappings
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'())
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;; Mappings for the union closure of all inputs.
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(map (lambda (dir)
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(file-system-mapping
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(source dir)
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(target dir)
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(writable? #f)))
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reqs))))
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(file-systems (append %container-file-systems
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(map file-system-mapping->bind-mount
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mappings))))
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@ -467,8 +482,7 @@ symbolic link from ~/.guix-profile to the environment profile."
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;; The same variables as in Nix's 'build.cc'.
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'("TMPDIR" "TEMPDIR" "TMP" "TEMP"))
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;; Create a dummy home directory under the same name as on the
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;; host.
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;; Create a dummy home directory.
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(mkdir-p home-dir)
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(setenv "HOME" home-dir)
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@ -495,7 +509,7 @@ symbolic link from ~/.guix-profile to the environment profile."
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;; For convenience, start in the user's current working
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;; directory rather than the root directory.
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(chdir cwd)
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(chdir (override-user-dir user home cwd))
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(primitive-exit/status
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;; A container's environment is already purified, so no need to
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@ -505,6 +519,60 @@ symbolic link from ~/.guix-profile to the environment profile."
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(delq 'net %namespaces) ; share host network
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%namespaces)))))))
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(define (mock-passwd passwd user-override shell)
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"Generate mock information for '/etc/passwd'. If USER-OVERRIDE is not '#f',
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it is expected to be a string representing the mock username; it will produce
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a user of that name, with a home directory of '/home/USER-OVERRIDE', and no
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GECOS field. If USER-OVERRIDE is '#f', data will be inherited from PASSWD.
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In either case, the shadow password and UID/GID are cleared, since the user
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runs as root within the container. SHELL will always be used in place of the
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shell in PASSWD.
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The resulting vector is suitable for use with Guile's POSIX user procedures.
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See passwd(5) for more information each of the fields."
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(if user-override
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(vector
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user-override
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"x" "0" "0" ;; no shadow, user is now root
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"" ;; no personal information
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(user-override-home user-override)
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shell)
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(vector
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(passwd:name passwd)
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"x" "0" "0" ;; no shadow, user is now root
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(passwd:gecos passwd)
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(passwd:dir passwd)
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shell)))
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(define (user-override-home user)
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"Return home directory for override user USER."
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(string-append "/home/" user))
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(define (override-user-mappings user home mappings)
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"If a username USER is provided, rewrite each HOME prefix in file system
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mappings MAPPINGS to a home directory determined by 'override-user-dir';
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otherwise, return MAPPINGS."
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(if (not user)
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mappings
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(map (lambda (mapping)
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(let ((target (file-system-mapping-target mapping)))
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(if (string-prefix? home target)
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(file-system-mapping
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(source (file-system-mapping-source mapping))
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(target (override-user-dir user home target))
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(writable? (file-system-mapping-writable? mapping)))
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mapping)))
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mappings)))
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(define (override-user-dir user home dir)
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"If username USER is provided, overwrite string prefix HOME in DIR with a
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directory determined by 'user-override-home'; otherwise, return DIR."
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(if (and user (string-prefix? home dir))
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(string-append (user-override-home user)
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(substring dir (string-length home)))
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dir))
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(define (link-environment profile home-dir)
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"Create a symbolic link from HOME-DIR/.guix-profile to PROFILE."
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(let ((profile-dir (string-append home-dir "/.guix-profile")))
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@ -592,6 +660,7 @@ message if any test fails."
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(container? (assoc-ref opts 'container?))
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(link-prof? (assoc-ref opts 'link-profile?))
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(network? (assoc-ref opts 'network?))
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(user (assoc-ref opts 'user))
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(bootstrap? (assoc-ref opts 'bootstrap?))
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(system (assoc-ref opts 'system))
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(command (or (assoc-ref opts 'exec)
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@ -626,6 +695,8 @@ message if any test fails."
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(when (and (not container?) link-prof?)
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(leave (G_ "'--link-profile' cannot be used without '--container'~%")))
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(when (and (not container?) user)
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(leave (G_ "'--user' cannot be used without '--container'~%")))
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(with-store store
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(set-build-options-from-command-line store opts)
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@ -673,6 +744,7 @@ message if any test fails."
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"/bin/sh"))))
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(launch-environment/container #:command command
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#:bash bash-binary
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#:user user
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#:user-mappings mappings
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#:profile profile
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#:paths paths
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@ -109,6 +109,17 @@ rm $tmpdir/mounts
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-- guile -c "$linktest"
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)
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# Test that user can be mocked.
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usertest='(exit (and (string=? (getenv "HOME") "/home/foognu")
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(string=? (passwd:name (getpwuid 0)) "foognu")
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(file-exists? "/home/foognu/umock")))'
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touch "$tmpdir/umock"
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HOME="$tmpdir" guix environment --bootstrap --container --user=foognu \
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--ad-hoc guile-bootstrap --pure \
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--share="$tmpdir/umock" \
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-- guile -c "$usertest"
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# Check the exit code.
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abnormal_exit_code="
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