diff --git a/Cargo.lock b/Cargo.lock
index 0deb91a09f..82e2a58061 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,7 +14,7 @@ dependencies = [
 
 [[package]]
 name = "arrayvec"
-version = "0.4.6"
+version = "0.4.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "nodrop 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -22,16 +22,14 @@ dependencies = [
 
 [[package]]
 name = "backtrace"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "backtrace-sys 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -39,13 +37,13 @@ name = "backtrace-sys"
 version = "0.1.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "bitflags"
-version = "0.7.0"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -53,13 +51,13 @@ name = "blake2-rfc"
 version = "0.2.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "arrayvec 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "cc"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -72,15 +70,6 @@ name = "constant_time_eq"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
-[[package]]
-name = "dbghelp-sys"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "extra"
 version = "0.1.0"
@@ -91,7 +80,7 @@ name = "failure"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure_derive 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -107,32 +96,21 @@ dependencies = [
 
 [[package]]
 name = "fuchsia-zircon"
-version = "0.2.1"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "fuchsia-zircon-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bitflags 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "fuchsia-zircon-sys"
-version = "0.2.0"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "kernel32-sys"
-version = "0.2.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
-]
 
 [[package]]
 name = "libc"
-version = "0.2.34"
+version = "0.2.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -156,16 +134,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "rand"
-version = "0.3.18"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "fuchsia-zircon 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "redox_syscall"
-version = "0.1.32"
+version = "0.1.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -173,18 +152,19 @@ name = "redox_termios"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "redox_syscall 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "redox_users"
 version = "0.1.0"
-source = "git+https://github.com/redox-os/users.git#90e5ffe4df14361e9032c35bd96c38be8558a822"
+source = "git+https://github.com/redox-os/users.git#70b8a69ce6588693d05f3500b481c2620c1ee824"
 dependencies = [
  "argon2rs 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "extra 0.1.0 (git+https://github.com/redox-os/libextra.git)",
  "failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -229,8 +209,8 @@ name = "termion"
 version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -249,11 +229,9 @@ name = "userutils"
 version = "0.1.0"
 dependencies = [
  "arg_parser 0.1.0 (git+https://github.com/redox-os/arg-parser.git)",
- "argon2rs 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "extra 0.1.0 (git+https://github.com/redox-os/libextra.git)",
  "liner 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_users 0.1.0 (git+https://github.com/redox-os/users.git)",
  "termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -261,38 +239,45 @@ dependencies = [
 
 [[package]]
 name = "winapi"
-version = "0.2.8"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
-name = "winapi-build"
-version = "0.1.1"
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [metadata]
 "checksum arg_parser 0.1.0 (git+https://github.com/redox-os/arg-parser.git)" = "<none>"
 "checksum argon2rs 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "3f67b0b6a86dae6e67ff4ca2b6201396074996379fba2b92ff649126f37cb392"
-"checksum arrayvec 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "2f0ef4a9820019a0c91d918918c93dc71d469f581a49b47ddc1d285d4270bbe2"
-"checksum backtrace 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8709cc7ec06f6f0ae6c2c7e12f6ed41540781f72b488d83734978295ceae182e"
+"checksum arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)" = "a1e964f9e24d588183fcb43503abda40d288c8657dfc27311516ce2f05675aef"
+"checksum backtrace 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "ebbbf59b1c43eefa8c3ede390fcc36820b4999f7914104015be25025e0d62af2"
 "checksum backtrace-sys 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)" = "44585761d6161b0f57afc49482ab6bd067e4edef48c12a152c237eb0203f7661"
-"checksum bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aad18937a628ec6abcd26d1489012cc0e18c21798210f491af69ded9b881106d"
+"checksum bitflags 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b3c30d3802dfb7281680d6285f2ccdaa8c2d8fee41f93805dba5c4cf50dc23cf"
 "checksum blake2-rfc 0.2.18 (registry+https://github.com/rust-lang/crates.io-index)" = "5d6d530bdd2d52966a6d03b7a964add7ae1a288d25214066fd4b600f0f796400"
-"checksum cc 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a9b13a57efd6b30ecd6598ebdb302cca617930b5470647570468a65d12ef9719"
+"checksum cc 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "deaf9ec656256bb25b404c51ef50097207b9cbb29c933d31f92cae5a8a0ffee0"
 "checksum cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d4c819a1287eb618df47cc647173c5c4c66ba19d888a6e50d605672aed3140de"
 "checksum constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
-"checksum dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "97590ba53bcb8ac28279161ca943a924d1fd4a8fb3fa63302591647c4fc5b850"
 "checksum extra 0.1.0 (git+https://github.com/redox-os/libextra.git)" = "<none>"
 "checksum failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "934799b6c1de475a012a02dab0ace1ace43789ee4b99bcfbf1a2e3e8ced5de82"
 "checksum failure_derive 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c7cdda555bb90c9bb67a3b670a0f42de8e73f5981524123ad8578aafec8ddb8b"
-"checksum fuchsia-zircon 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f6c0581a4e363262e52b87f59ee2afe3415361c6ec35e665924eb08afe8ff159"
-"checksum fuchsia-zircon-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "43f3795b4bae048dc6123a6b972cadde2e676f9ded08aef6bb77f5f157684a82"
-"checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
-"checksum libc 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)" = "36fbc8a8929c632868295d0178dd8f63fc423fd7537ad0738372bd010b3ac9b0"
+"checksum fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2e9763c69ebaae630ba35f74888db465e49e259ba1bc0eda7d06f4a067615d82"
+"checksum fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
+"checksum libc 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)" = "1e5d97d6708edaa407429faa671b942dc0f2727222fb6b6539bf1db936e4b121"
 "checksum liner 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f9e406164c25b420480023985bdf65cef366855666ad4cb12cd3eaee82dcb399"
 "checksum nodrop 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "9a2228dca57108069a5262f2ed8bd2e82496d2e074a06d1ccc7ce1687b6ae0a2"
 "checksum quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e920b65c65f10b2ae65c831a81a073a89edd28c7cce89475bff467ab4167a"
-"checksum rand 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)" = "6475140dfd8655aeb72e1fd4b7a1cc1c202be65d71669476e392fe62532b9edd"
-"checksum redox_syscall 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)" = "ab105df655884ede59d45b7070c8a65002d921461ee813a024558ca16030eea0"
+"checksum rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "eba5f8cb59cc50ed56be8880a5c7b496bfd9bd26394e176bc67884094145c2c5"
+"checksum redox_syscall 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)" = "0d92eecebad22b767915e4d529f89f28ee96dbbf5a4810d2b844373f136417fd"
 "checksum redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7e891cfe48e9100a70a3b6eb652fef28920c117d366339687bd5576160db0f76"
 "checksum redox_users 0.1.0 (git+https://github.com/redox-os/users.git)" = "<none>"
 "checksum rustc-demangle 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "aee45432acc62f7b9a108cc054142dac51f979e69e71ddce7d6fc7adf29e817e"
@@ -303,5 +288,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "689a3bdfaab439fd92bc87df5c4c78417d3cbe537487274e9b0b2dce76e92096"
 "checksum unicode-width 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "bf3a113775714a22dcb774d8ea3655c53a32debae63a063acc00a91cc586245f"
 "checksum unicode-xid 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8c1f860d7d29cf02cb2f3f359fd35991af3d30bac52c57d265a3c461074cb4dc"
-"checksum winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "167dc9d6949a9b857f3451275e911c3f44255842c1f7a76f33c55103a909087a"
-"checksum winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "2d315eee3b34aca4797b2da6b13ed88266e6d612562a0c46390af8299fc699bc"
+"checksum winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "04e3bd221fcbe8a271359c04f21a76db7d0c6028862d1bb5512d85e1e2eb5bb3"
+"checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+"checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/Cargo.toml b/Cargo.toml
index 652998ea8c..3d48fc87f6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -39,11 +39,9 @@ name = "whoami"
 path = "src/bin/whoami.rs"
 
 [dependencies]
-argon2rs = { version = "0.2", default-features = false }
 arg_parser = { git = "https://github.com/redox-os/arg-parser.git" }
 extra = { git = "https://github.com/redox-os/libextra.git" }
 liner = "0.1"
-rand = "0.3"
 redox_syscall = "0.1"
 redox_termios = "0.1"
 redox_users = { git = "https://github.com/redox-os/users.git" }
diff --git a/src/bin/groupadd.rs b/src/bin/groupadd.rs
index f1bd2ef106..d5dbbd1c22 100644
--- a/src/bin/groupadd.rs
+++ b/src/bin/groupadd.rs
@@ -11,7 +11,7 @@ use std::io::Write;
 use std::process::exit;
 
 use arg_parser::ArgParser;
-use redox_users::{add_group, get_group_by_id, get_unique_group_id, UsersError};
+use redox_users::{AllGroups, UsersError};
 
 const MAN_PAGE: &'static str = /* @MANSTART{groupadd} */ r#"
 NAME
@@ -60,6 +60,8 @@ fn main() {
         stdout.flush().try(&mut stderr);
         exit(0);
     }
+    
+    let mut sys_groups = AllGroups::new().unwrap_or_exit(1);
 
     let groupname = if parser.args.is_empty() {
         eprintln!("groupadd: no group name specified");
@@ -69,23 +71,19 @@ fn main() {
     };
 
     let gid = if let Some(gid) = parser.get_opt("gid") {
-        let gid = gid.parse::<u32>().unwrap_or_exit(1);
+        let gid = gid.parse::<usize>().unwrap_or_exit(1);
 
-        match get_group_by_id(gid as usize) {
-            Ok(_) => {
+        match sys_groups.get_by_id(gid) {
+            Some(_) => {
                 eprintln!("groupadd: group already exists");
                 exit(1);
             },
-            Err(ref err) if err.downcast_ref::<UsersError>() == Some(&UsersError::AlreadyExists) => {
+            None => {
                 gid
-            },
-            Err(err) => {
-                eprintln!("groupadd: {}", err);
-                exit(1);
             }
         }
     } else {
-        match get_unique_group_id() {
+        match sys_groups.get_unique_id() {
             Some(gid) => gid,
             None => {
                 eprintln!("groupadd: no available gid");
@@ -94,7 +92,7 @@ fn main() {
         }
     };
 
-    match add_group(groupname, gid, &[""]) {
+    match sys_groups.add_group(groupname, gid, &[""]) {
         Ok(_) => { },
         Err(ref err) if err.downcast_ref::<UsersError>() == Some(&UsersError::AlreadyExists) && parser.found("force") => {
             exit(0);
@@ -104,4 +102,5 @@ fn main() {
             exit(1);
         }
     }
+    sys_groups.save().unwrap_or_exit(1);
 }
diff --git a/src/bin/id.rs b/src/bin/id.rs
index 3b13a79a75..69e697ae73 100644
--- a/src/bin/id.rs
+++ b/src/bin/id.rs
@@ -11,7 +11,7 @@ use std::process::exit;
 use extra::io::fail;
 use extra::option::OptionalExt;
 use arg_parser::{ArgParser, Param};
-use redox_users::{get_egid, get_gid, get_euid, get_uid, get_user_by_id, get_group_by_id};
+use redox_users::{get_egid, get_gid, get_euid, get_uid, AllUsers, AllGroups};
 
 const HELP_INFO: &'static str = "Try ‘id --help’ for more information.\n";
 const MAN_PAGE: &'static str = /* @MANSTART{id} */ r#"
@@ -86,6 +86,9 @@ pub fn main() {
         print_msg(HELP_INFO, &mut stdout, &mut stderr);
         exit(1);
     }
+    
+    let groups = AllGroups::new().unwrap_or_exit(1);
+    let users = AllUsers::new().unwrap_or_exit(1);
 
     // Display the different group IDs (effective and real)
     // as white-space separated numbers, in no particular order.
@@ -123,8 +126,7 @@ pub fn main() {
         };
 
         let uid = uid_result.unwrap_or_exit(1);
-
-        let user = get_user_by_id(uid).unwrap_or_exit(1);
+        let user = users.get_by_id(uid).unwrap_or_exit(1);
 
         print_msg(&format!("{}\n", user.user), &mut stdout, &mut stderr);
         exit(0);
@@ -156,8 +158,9 @@ pub fn main() {
         };
 
         let gid = gid_result.unwrap_or_exit(1);
-
-        let group = get_group_by_id(gid).unwrap_or_exit(1);
+        
+        let groups = AllGroups::new().unwrap_or_exit(1);
+        let group = groups.get_by_id(gid).unwrap_or_exit(1);
 
         print_msg(&format!("{}\n", group.group), &mut stdout, &mut stderr);
         exit(0);
@@ -195,10 +198,10 @@ pub fn main() {
     let euid = get_euid().unwrap_or_exit(1);
 
     let egid = get_egid().unwrap_or_exit(1);
+    
+    let user = users.get_by_id(euid).unwrap_or_exit(1);
 
-    let user = get_user_by_id(euid).unwrap_or_exit(1);
-
-    let group = get_group_by_id(egid).unwrap_or_exit(1);
+    let group = groups.get_by_id(egid).unwrap_or_exit(1);
 
     let msg = format!("uid={}({}) gid={}({})\n", euid, user.user, egid, group.group);
     print_msg(&msg, &mut stdout, &mut stderr);
diff --git a/src/bin/login.rs b/src/bin/login.rs
index 8e98e38f97..8708eab68c 100644
--- a/src/bin/login.rs
+++ b/src/bin/login.rs
@@ -16,7 +16,7 @@ use std::str;
 use extra::option::OptionalExt;
 use arg_parser::ArgParser;
 use termion::input::TermRead;
-use redox_users::{get_user_by_name, UsersError};
+use redox_users::{AllUsers};
 use userutils::spawn_shell;
 
 const MAN_PAGE: &'static str = /* @MANSTART{login} */ r#"
@@ -67,22 +67,12 @@ pub fn main() {
             .read_line("\x1B[1mredox login:\x1B[0m ", &mut |_| {})
             .try(&mut stderr);
 
-        if ! user.is_empty() {
+        if !user.is_empty() {
             let stdin = io::stdin();
             let mut stdin = stdin.lock();
+            let sys_users = AllUsers::new().unwrap_or_exit(1);
 
-            let user_option = match get_user_by_name(user) {
-                Ok(user) => Some(user),
-                Err(ref err) if err.downcast_ref::<UsersError>() == Some(&UsersError::NotFound) => {
-                    None
-                },
-                Err(err) => {
-                    println!("login: {}", err);
-                    exit(1);
-                }
-            };
-
-            match user_option {
+            match sys_users.get_by_name(user) {
                 None => {
                     stdout.write(b"\nLogin incorrect\n").try(&mut stderr);
                     stdout.write(b"\n").try(&mut stderr);
@@ -90,13 +80,13 @@ pub fn main() {
                     continue;
                 },
                 Some(user) => {
-                    if user.hash == "" {
+                    if user.is_passwd_blank() {
                         if let Ok(mut motd) = File::open(MOTD_FILE) {
                             io::copy(&mut motd, &mut stdout).try(&mut stderr);
                             stdout.flush().try(&mut stderr);
                         }
 
-                        spawn_shell(user);
+                        spawn_shell(user).unwrap_or_exit(1);
                         break;
                     }
 
@@ -112,7 +102,7 @@ pub fn main() {
                                 stdout.flush().try(&mut stderr);
                             }
 
-                            spawn_shell(user);
+                            spawn_shell(user).unwrap_or_exit(1);
                             break;
                         }
                     }
@@ -123,4 +113,4 @@ pub fn main() {
             stdout.flush().try(&mut stderr);;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/bin/passwd.rs b/src/bin/passwd.rs
index 475ecd6974..58b311ad3f 100644
--- a/src/bin/passwd.rs
+++ b/src/bin/passwd.rs
@@ -2,11 +2,9 @@
 
 extern crate arg_parser;
 extern crate extra;
-extern crate rand;
 extern crate termion;
 extern crate redox_users;
 
-use rand::{Rng, OsRng};
 use std::{env, io};
 use std::io::Write;
 use std::process::exit;
@@ -14,7 +12,7 @@ use std::process::exit;
 use arg_parser::ArgParser;
 use extra::option::OptionalExt;
 use termion::input::TermRead;
-use redox_users::{User, get_uid, get_user_by_id, get_user_by_name};
+use redox_users::{get_uid, AllUsers};
 
 const MAN_PAGE: &'static str = /* @MANSTART{passwd} */ r#"
 NAME
@@ -58,76 +56,72 @@ fn main() {
     }
 
     let uid = get_uid().unwrap_or_exit(1);
+    let mut users = AllUsers::new().unwrap_or_exit(1);
     
-    let user = if parser.args.is_empty() {
-        get_user_by_id(uid).unwrap_or_exit(1)
-    } else {
-        let username = &parser.args[0];
-        get_user_by_name(username).unwrap_or_exit(1)
-    };
+    {
+        let user = if parser.args.is_empty() {
+            users.get_mut_by_id(uid).unwrap_or_exit(1)
+        } else {
+            let username = &parser.args[0];
+            users.get_mut_by_name(username).unwrap_or_exit(1)
+        };
 
-    let uid = uid as u32;
-    if user.uid == uid || uid == 0 {
-        let msg = format!("changing password for '{}' \n", user.user);
-        stdout.write_all(&msg.as_bytes()).try(&mut stderr);
-        stdout.flush().try(&mut stderr);
-
-        let mut verified = false;
-        if user.hash == "" {
-            verified = true;
-        } else if user.uid == uid || uid != 0 {
-            stdout.write_all(b"current password: ").try(&mut stderr);
+        if user.uid == uid || uid == 0 {
+            let msg = format!("changing password for '{}' \n", user.user);
+            stdout.write_all(&msg.as_bytes()).try(&mut stderr);
             stdout.flush().try(&mut stderr);
 
-            if let Some(password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
-                stdout.write(b"\n").try(&mut stderr);
+            let mut verified = false;
+            if user.is_passwd_blank() {
+                verified = true;
+            } else if user.uid == uid || uid != 0 {
+                stdout.write_all(b"current password: ").try(&mut stderr);
                 stdout.flush().try(&mut stderr);
 
-                if user.verify_passwd(&password) {
-                    verified = true;
-                }
-            }
-        } else {
-            verified = true;
-        }
-
-        if verified {
-            stdout.write_all(b"new password: ").try(&mut stderr);;
-            stdout.flush().try(&mut stderr);;
-
-            if let Some(new_password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
-                stdout.write(b"\nconfirm password: ").try(&mut stderr);
-                stdout.flush().try(&mut stderr);
-
-                if let Some(confirm_password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
+                if let Some(password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
                     stdout.write(b"\n").try(&mut stderr);
-                    stdout.flush().try(&mut stderr);;
+                    stdout.flush().try(&mut stderr);
 
-                    if new_password == confirm_password {
-                        let salt = format!("{:X}", OsRng::new().try(&mut stderr).next_u64());
-                        let encoded_passwd = User::encode_passwd(&new_password, &salt);
-                        // TODO: Actually persist the new password to PASSWD_FILE
-                        let msg = format!("{}\n", encoded_passwd);
-                        stdout.write_all(&msg.as_bytes()).try(&mut stderr);
-                        stdout.flush().try(&mut stderr);
+                    verified = user.verify_passwd(&password)
+                }
+            } else {
+                verified = true;
+            }
+
+            if verified {
+                stdout.write_all(b"new password: ").try(&mut stderr);;
+                stdout.flush().try(&mut stderr);;
+
+                if let Some(new_password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
+                    stdout.write(b"\nconfirm password: ").try(&mut stderr);
+                    stdout.flush().try(&mut stderr);
+
+                    if let Some(confirm_password) = stdin.read_passwd(&mut stdout).try(&mut stderr) {
+                        stdout.write(b"\n").try(&mut stderr);
+                        stdout.flush().try(&mut stderr);;
+
+                        if new_password == confirm_password {
+                            user.set_passwd(&new_password).unwrap_or_exit(1);
+                        } else {
+                            eprintln!("passwd: new password does not match confirm password");
+                            exit(1);
+                        }
                     } else {
-                        eprintln!("passwd: new password does not match confirm password");
+                        eprintln!("passwd: no confirm password provided");
                         exit(1);
                     }
                 } else {
-                    eprintln!("passwd: no confirm password provided");
+                    eprintln!("passwd: no new password provided");
                     exit(1);
                 }
             } else {
-                eprintln!("passwd: no new password provided");
+                eprintln!("passwd: incorrect current password");
                 exit(1);
             }
         } else {
-            eprintln!("passwd: incorrect current password");
+            eprintln!("passwd: you do not have permission to set the password of '{}'", user.user);
             exit(1);
         }
-    } else {
-        eprintln!("passwd: you do not have permission to set the password of '{}'", user.user);
-        exit(1);
     }
+    users.save().unwrap_or_exit(1);
 }
diff --git a/src/bin/su.rs b/src/bin/su.rs
index 57ae650ad8..e83181c071 100644
--- a/src/bin/su.rs
+++ b/src/bin/su.rs
@@ -14,7 +14,7 @@ use std::str;
 use arg_parser::ArgParser;
 use extra::option::OptionalExt;
 use termion::input::TermRead;
-use redox_users::{get_uid, get_user_by_name};
+use redox_users::{get_uid, AllUsers};
 use userutils::spawn_shell;
 
 const MAN_PAGE: &'static str = /* @MANSTART{su} */ r#"
@@ -52,8 +52,7 @@ pub fn main() {
 
     // Shows the help
     if parser.found("help") {
-        stdout.write_all(MAN_PAGE.as_bytes()).try(&mut stderr);
-        stdout.flush().try(&mut stderr);
+        write!(stdout, "{}", MAN_PAGE).unwrap_or_exit(1);
         exit(0);
     }
 
@@ -64,37 +63,29 @@ pub fn main() {
     };
 
     let uid = get_uid().unwrap_or_exit(1);
+    
+    let users = AllUsers::new().unwrap_or_exit(1);
+    let user = users.get_by_name(&target_user).unwrap_or_exit(1);
 
-    let user = get_user_by_name(&target_user).unwrap_or_exit(1);
-
-    // If we are root and the new user account has no password
-    if uid == 0 && user.hash == "" {
-        stdout.write(b"\n").try(&mut stderr);
-        stdout.flush().try(&mut stderr);
-
-        // Spawn a shell as the new user
-        exit(spawn_shell(user).code().unwrap_or(1));
+    // If the user executing su is root, then they can do anything without a password.
+    // Same if the user we're being asked to login as doesn't have a password.
+    if uid == 0 || user.is_passwd_blank() {
+        writeln!(stdout).unwrap_or_exit(1);
+        exit(spawn_shell(user).unwrap_or_exit(1));
     } else {
-        // Ask for the new user account's password
-        stdout.write_all(b"password: ").try(&mut stderr);
-        stdout.flush().try(&mut stderr);
+        write!(stdout, "password: ").unwrap_or_exit(1);
+        stdout.flush().unwrap_or_exit(1);
 
         // Read the password, reading an empty string if CTRL-d is specified
         let password = stdin.read_passwd(&mut stdout).try(&mut stderr).unwrap_or(String::new());
 
-        // Write a newline
-        stdout.write(b"\n").try(&mut stderr);
-        stdout.flush().try(&mut stderr);
+        writeln!(stderr, "\n").unwrap_or_exit(1);
 
-        // If the password is correct
         if user.verify_passwd(&password) {
-            // Spawn a shell as the new user
-            exit(spawn_shell(user).code().unwrap_or(1));
+            exit(spawn_shell(user).unwrap_or_exit(1));
+        } else {
+            writeln!(stderr, "su: authentication failed").unwrap_or_exit(1);
+            exit(1);
         }
     }
-
-    // All other conditions will return an error
-    stderr.write(b"su: authentication failed\n").try(&mut stderr);
-    stderr.flush().try(&mut stderr);
-    exit(1);
 }
diff --git a/src/bin/sudo.rs b/src/bin/sudo.rs
index 20c09af981..200feee453 100644
--- a/src/bin/sudo.rs
+++ b/src/bin/sudo.rs
@@ -14,7 +14,7 @@ use std::process::{Command, exit};
 use arg_parser::ArgParser;
 use extra::option::OptionalExt;
 use termion::input::TermRead;
-use redox_users::{get_uid, get_user_by_id, get_group_by_name};
+use redox_users::{get_uid, AllUsers, AllGroups};
 
 const MAX_ATTEMPTS: u16 = 3;
 const MAN_PAGE: &'static str = /* @MANSTART{sudo} */ r#"
@@ -66,17 +66,20 @@ pub fn main() {
         eprintln!("sudo: no command provided");
         exit(1);
     });
-
+    
+    let users = AllUsers::new().unwrap_or_exit(1);
+    let groups = AllGroups::new().unwrap_or_exit(1);
+    
     let uid = get_uid().unwrap_or_exit(1);
 
-    let user = get_user_by_id(uid).unwrap_or_exit(1);
+    let user = users.get_by_id(uid).unwrap_or_exit(1);
 
     if uid != 0 {
-        let sudo_group = get_group_by_name("sudo").unwrap_or_exit(1);
+        let sudo_group = groups.get_by_name("sudo").unwrap_or_exit(1);
 
         if sudo_group.users.iter().any(|name| name == &user.user) {
-            if ! user.hash.is_empty() {
-                let max_attempts = MAX_ATTEMPTS;
+            //If the user's password is not empty...
+            if !user.is_passwd_blank() {
                 let mut attempts = 0;
 
                 loop {
@@ -92,8 +95,8 @@ pub fn main() {
                                 break;
                             } else {
                                 attempts += 1;
-                                eprintln!("sudo: incorrect password ({}/{})", attempts, max_attempts);
-                                if attempts >= max_attempts {
+                                eprintln!("sudo: incorrect password ({}/{})", attempts, MAX_ATTEMPTS);
+                                if attempts >= MAX_ATTEMPTS {
                                     exit(1);
                                 }
                             }
diff --git a/src/bin/useradd.rs b/src/bin/useradd.rs
index 28bb873cc8..ddc2eb28f4 100644
--- a/src/bin/useradd.rs
+++ b/src/bin/useradd.rs
@@ -12,7 +12,7 @@ use std::process::exit;
 
 use arg_parser::ArgParser;
 use extra::option::OptionalExt;
-use redox_users::{add_group, add_user, get_unique_group_id, get_unique_user_id};
+use redox_users::{AllGroups, AllUsers};
 
 const MAN_PAGE: &'static str = /* @MANSTART{useradd} */ r#"
 NAME
@@ -100,16 +100,19 @@ fn main() {
         &parser.args[0]
     };
     
+    let mut sys_users = AllUsers::new().unwrap_or_exit(1);
+    let mut sys_groups = AllGroups::new().unwrap_or_exit(1);
+    
     let uid = if parser.found("uid") {
         match parser.get_opt("uid") {
-            Some(uid) => uid.parse::<u32>().unwrap_or_exit(1),
+            Some(uid) => uid.parse::<usize>().unwrap_or_exit(1),
             None => {
                 eprintln!("useradd: missing uid value");
                 exit(1);
             }
         }
     } else {
-        match get_unique_user_id() {
+        match sys_users.get_unique_id() {
             Some(id) => id,
             None => {
                 eprintln!("useradd: no available uid");
@@ -119,21 +122,21 @@ fn main() {
     };
     
     //This is a ridiculous mess and could use reworking
-    let gid: u32;
+    let gid: usize;
     if parser.found("no-user-group") {
         gid = 99;
         //TODO: Add this user to the "nobody" group
     } else {
         if parser.found("gid") {
             gid = match parser.get_opt("gid") {
-                Some(gid) => gid.parse::<u32>().unwrap_or_exit(1),
+                Some(gid) => gid.parse::<usize>().unwrap_or_exit(1),
                 None => {
                     eprintln!("useradd: missing gid argument");
                     exit(1);
                 }
             };
         } else {
-            gid = match get_unique_group_id() {
+            gid = match sys_groups.get_unique_id() {
                 Some(id) => id,
                 None => {
                     eprintln!("useradd: no available gid");
@@ -141,7 +144,7 @@ fn main() {
                 }
             };
         }
-        match add_group(login, gid, &[login]) {
+        match sys_groups.add_group(login, gid, &[login]) {
             Ok(_) => {},
             Err(err) => {
                 eprintln!("useradd: error creating group {}: {}", login, err);
@@ -188,7 +191,7 @@ fn main() {
         DEFAULT_SHELL.to_string()
     };
     
-    match add_user(login, uid, gid, username.as_str(), userhome.as_str(), shell.as_str()) {
+    match sys_users.add_user(login, uid, gid, username.as_str(), userhome.as_str(), shell.as_str()) {
         Ok(_) => {},
         Err(err) => {
             eprintln!("useradd: {}: {}", err, login);
@@ -209,4 +212,6 @@ fn main() {
             }
         };
     }
+    sys_users.save().unwrap_or_exit(1);
+    sys_groups.save().unwrap_or_exit(1);
 }
diff --git a/src/bin/whoami.rs b/src/bin/whoami.rs
index d85e8286bd..c7b8bed3b2 100644
--- a/src/bin/whoami.rs
+++ b/src/bin/whoami.rs
@@ -9,7 +9,7 @@ use std::process::exit;
 use std::env;
 use arg_parser::ArgParser;
 use extra::option::OptionalExt;
-use redox_users::{get_euid, get_user_by_id};
+use redox_users::{get_euid, AllUsers};
 
 const MAN_PAGE: &'static str = /* @MANSTART{whoami} */ r#"
 NAME
@@ -49,8 +49,9 @@ fn main() {
     }
 
     let euid = get_euid().unwrap_or_exit(1);
-
-    let user = get_user_by_id(euid).unwrap_or_exit(1);
+    
+    let users = AllUsers::new().unwrap_or_exit(1);
+    let user = users.get_by_id(euid).unwrap_or_exit(1);
 
     println!("{}", user.user);
     exit(0);
diff --git a/src/lib.rs b/src/lib.rs
index b29b2ac7d2..95323ebf64 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,56 +18,31 @@
 
 extern crate redox_users;
 
-use std::process::{Command, ExitStatus};
-use std::os::unix::process::CommandExt;
+use std::io::Result;
 
 use redox_users::User;
 
 /// Spawns a shell for the given `User`.
 ///
-/// The new the shell process will have set the users UID and GID, its CWD will be
-/// set to the users's home directory and the follwing enviroment variables will
-/// be populated like so:
-///
-///    - `USER` set to the user's `user` field.
-///    - `UID` set to the user's `uid` field.
-///    - `GROUPS` set the user's `gid` field.
-///    - `HOME` set to the user's `home` field.
-///    - `SHELL` set to the user's `shell` field.
+/// This function wraps the shell_cmd function of the User struct
+/// from redox_users and manages the child process. It is a blocking
+/// operation.
 ///
 /// # Examples
 ///
 /// ```
-/// use redox_users::get_user_by_name;
+/// use redox_users::AllUsers;
 ///
-/// let user = get_user_by_name("goyox86");
-/// spawn_shell(user);
+/// let sys_users = AllUsers::new().unwrap();
+/// let user = sys_users.get_by_name("goyox86");
+/// spawn_shell(user).unwrap();
 /// ```
-///
-/// # Panics
-///
-/// This function can panic under two scenarios. The first, when an error occurs while
-/// spawning the new process containig the shell and the second, when after a succesful
-/// spawn, an error happens while trying to wait for the newly created process.
-pub fn spawn_shell(user: User) -> ExitStatus {
-    let mut command = Command::new(&user.shell);
+pub fn spawn_shell(user: &User) -> Result<i32> {
+    let mut command = user.shell_cmd();
 
-    command.uid(user.uid);
-    command.gid(user.gid);
-
-    command.current_dir(&user.home);
-
-    command.env("USER", &user.user);
-    command.env("UID", format!("{}", user.uid));
-    command.env("GROUPS", format!("{}", user.gid));
-    command.env("HOME", &user.home);
-    command.env("SHELL", &user.shell);
-
-    match command.spawn() {
-        Ok(mut child) => match child.wait() {
-            Ok(status) => status,
-            Err(err) => panic!("userutils: failed to wait for '{}': {}", user.shell, err)
-        },
-        Err(err) => panic!("userutils: failed to execute '{}': {}", user.shell, err)
+    let mut child = command.spawn()?;
+    match child.wait()?.code() {
+        Some(code) => Ok(code),
+        None => Ok(1)
     }
 }