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  1. Introduction
  2. About Linux
  3. Installation and getting started
  4. Logging in and out
  5. Basic Linux Commands
  6. Linux Files and File Permissions
  7. Linux Directory Structure
  8. Finding Files
  9. Linux Help
  10. Setting Time
  11. Devices
  12. Tips
  13. Accessing Other Filesystems
  14. Accessing Removable Media
  15. Making and Managing Filesystems
  16. Emergency Filesystems and Procedures
  17. LILO and Runlevels
  18. Init
  19. Environment, Shell Selection, and Startu
  20. Linux Kernel
  21. Package Installation and Printing
  22. Configuration, Logging and CRON
  23. Keys and Terminal Configuration
  24. Sound Configuration
  25. Managing Users
  26. Passwords
  27. Process Control
  28. Configuration and Diagnostic Tools
  29. Overall Configuration
  30. Using PAM
  31. Basic Network Setup
  32. Tools and Terms
  33. Novell and Printing
  34. Inetd Services
  35. Xinetd Services
  36. Other Network Services
  37. FTP and Telnet
  38. Samba
  39. Identd (auth)
  40. X Configuration
  41. X Use
  42. Using X Remotely
  43. X Documentation
  44. DNS
  45. DHCP and BOOTP
  46. Apache
  47. NFS
  48. PPP
  49. Mail
  50. Routing
  51. IP Masquerading
  52. Proxy Servers and ipchains
  53. UUCP
  54. News
  55. NIS
  56. Network Security
  57. Secure Shell
  58. Text Processing
  59. Shell Programming
  60. Emacs
  61. VI
  62. Recommended Reading
  63. Credits

Linux Passwords

Most versions of Linux come with the shadow password suite of software already installed. This suite of software is recommended to enhance security since all users must be able to access the /etc/passwd file. With full access to this file, a "crack" program can be used by any user to extract all passwords on the system. The shadow password software places the actual encrypted passwords into the /etc/shadow file making this file readable only by the root user. If your system has the file /etc/shadow, you probably already have shadow passwords installed.

Linux Shadow Passwords

If your system did not come with shadow passwords and you are going to install it you will want to read the Shadow-Password-HOWTO and roughly do the following.

  1. Find the latest shadow password suite that will work on your system
  2. Backup a copy of your files listed above that the shadow password suite will replace.
  3. Install the shadow password suite.
  4. Remove old man pages that may interfere with you seeing the correct replacement man pages that came with the shadow password suite.
  5. run pwconv which creates /etc/npasswd and /etc/nshadow
  6. Backup /etc/passwd and copy the files /etc/npasswd and /etc/nshadow to /etc/passwd and /etc/shadow respectively.
  7. Be sure the /etc/shadow and /etc/passwd owners and permissions are the same as shown in listings in this manual.
  8. Verify you can login
  9. When you are sure the system runs OK, remove backup files such as the backed up copy of /etc/passwd.
  10. You may need to upgrade your xlock program to get X working. xlock is the screen saver used to lock the screen.
  11. xdm presents the login screen for X. You may need to upgrade xdm.