Week Eleven Agenda

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Week Eleven Agenda. Announcements Open Source Presentation dates December 7 and 14 Lab Assignment 11-1 No script logic Link of the week Review week ten lab assignment Week ten expected outcomes Next lab assignment Break-out problems Upcoming deadlines Lab assistance.
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Week Eleven Agenda
  • Announcements
  • Open Source Presentation dates
  • December 7 and 14
  • Lab Assignment 11-1 No script logic
  • Link of the week
  • Review week ten lab assignment
  • Week ten expected outcomes
  • Next lab assignment
  • Break-out problems
  • Upcoming deadlines
  • Lab assistance
  • Link of the week File System  http://www.skillsheaven.com/linuxfil.php This site addresses every concern you might have about Linux from history, version types, pros and cons, trouble shooting, file system, and downloads. Define File System The methods, organization of data, and metadata that an operating system uses to keep track of files on a disk or partition on a storage device. Link of the week Linux File system ext3 includes journaling capabilities that allows for faster recovery after unexpected reboots. Journaling reduces the amount of time spent recovering a file system after a crash, and is therefore in high demand in environments where high availability is important, not only to improve recovery times on single machines but also to allow a crashed machine's file system to be recovered on another machine when we have a cluster of nodes with a shared disk. Link of the week Define file system with journaling : A file system with journaling is based on the techniques used from real-time transaction processing. A transaction log is used to store transactions either in a designated file system location or on a separate disk partition. As changes are made to the file system, metadata changes are recorded in the log and writing entries in the log are done prior to writing the actual buffers to disk. Link of the week Linux file system with journaling In the event of a system crash, the entries in the log file remain intact and are replayed. Maintaining this level of data integrity ensures that the file system is in a constant state. Review week ten lab assignment Definition: Network Protocol is a standard procedure and format that two data communication devices must understand, accept and use in order to be able to communicate with each other. A network protocol determines the following: 1. The type of error checking to be performed. 2. The data compression method to be used. 3. How the sending device will indicate that it has finished sending a message. 4. How the receiving device will indicate that it has received a message. Review week ten lab assignment /etc/password file Location: /etc/passwd Field separators: Colon (:) File format: Username:Password:UID:GID:UserID:Home directory:Command/shell Example: dandrear:x:1020:1021:dandrear user:/export/home/dandrear:/bin/ksh Permissions on Einstein: -rw-r--r-- 1 root root 1636 Aug 16 10:37 /etc/passwd Review week ten lab assignment /etc/passwd file
  • Username: It is used when user logs in. It should be between 1 and 32 characters in length.
  • Password: An x character indicates that encrypted password is stored in /etc/shadow file.
  • User ID (UID): Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-99 are reserved for other predefined accounts. Further UID 100-999 are reserved by system for administrative and system accounts/groups.
  • Group ID (GID): The primary group ID (stored in /etc/group file)
  • User ID Info: The comment field. It allow you to add extra information about the users such as user’s full name, phone number etc. This field use by finger command.
  • Home directory: The absolute path to the directory the user will be in when they log in. If this directory does not exists then users directory becomes /
  • Command/shell: The absolute path of a command or shell (/bin/bash). Typically, this is a shell. Please not it does not have to be a shell.
  • Review week ten lab assignment Example of /etc/passwd file root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin sync:x:5:0:sync:/sbin:/bin/sync shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown halt:x:7:0:halt:/sbin:/sbin/halt Review week ten lab assignment /etc/passwd file The /etc/passwd file is considered the user database for the system. The information contained in the /etc/passwd file is useful for applications running on the system to access. In summary, the /etc/passwd file is located under the system configuration and executables directory. The /etc/passwd file is the system’s master list of information about user accounts. Review week ten lab assignment /etc/shadow file Location: /etc/shadow Field separators: Colon (:) File format: username:passwd:lastpasswdch:min:max:warn:inactive:expire:unused Example: dandrear:$1$dhBysgdhfteM9gd00:13064:0:99999:7::: Permissions on Einstein: -r-------- 1 root root 1107 Sep 5 15:24 /etc/shadow (Permission denied) Review week ten lab assignment /etc/shadow file
  • User name : It is your login name
  • Password: It your encrypted password. The password should be minimum 6-8 characters long including special characters/digits
  • Last password change (last changed): Days since Jan 1, 1970 that password was last changed
  • Minimum: The minimum number of days required between password changes i.e. the number of days left before the user is allowed to change his/her password
  • Maximum: The maximum number of days the password is valid (after that user is forced to change his/her password)
  • Warn : The number of days before password is to expire that user is warned that his/her password must be changed
  • Inactive : The number of days after password expires that account is disabled
  • Expire : days since Jan 1, 1970 that account is disabled i.e. an absolute date specifying when the login may no longer be used
  • Unused field:
  • Review week ten lab assignment /etc/shadow file
  • The “X” in the /etc/passwd file password field indicates that the shadow file contains the encrypted password.
  • Red Hat Linux uses MD5 by default.
  • Most Linux systems utilize MD5 as their encrypted form.
  • MD5 requires 34 characters in encryption form.
  • MD5 begins with a dollar sign, number, and a dollar sign (e.g. $1$ or $6$ …).
  • The shadow file is only readable by root. In summary, the /etc/shadow file contains the encoded passwords and password settings. The /etc/shadow file contains all the guide lines that pertain to the administration of the password.
  • Review week ten lab assignment /etc/group file Location: /etc/group Field separators: Colon (:) File format: Group name:Password:GID:User_list Example: faculty:x:410: staff:x:430: Permissions on Einstein: -rw-r--r-- 1 root root 833 Aug 16 10:37 group Review week ten lab assignment /etc/group file
  • Group name: Name of the group.
  • Password: The group password is encrypted. If this field is empty, no password is needed. Otherwise, an “X” in the field indicates the password is stored in the /etc/gshadow file.
  • GID: The numerical group ID and/or unique group identifier.
  • User_list: All the group member's user names, separated by commas. Most Unix-like systems impose a limit of 16 to 32 group memberships per user.
  • Review week ten lab assignment /etc/group file ntp:x:38: student:x:101: itadmin:x:400: faculty:x:410: csfac:x:420:mccannp,sieberth,hochstew,whittakt,morganr,hartung staff:x:430: hpsmh:x:501: kumarp:x:503: caldwelr:x:505: apache:x:48: oinstall:x:600: Linux utilizes the vigr command used to edit the /etc/group file. Review week ten lab assignment /etc/group file In summary, the /etc/group file identifies a collection of users who generally share similar functions. These groupings are not limited to departments or project. Review week ten lab assignment /etc/gshadow file
  • Group-name: is the name of the group
  • Password: is the encoded version of the password
  • Group-admins: is the list of members in the group
  • Additional- users: a copy of additional members. In summary, the /etc/gshadow file is utilized to store the /etc/group password.
  • Review week ten lab assignment File Summary /etc/passwd - user account information /etc/shadow - secure user password information /etc/group - group information /etc/gshadow - secure group password information User account files The /etc/passwd, /etc/shadow, and /etc/group files are considered the most important files for storing user account and authentication information. Command to add a user account Linux/Knoppix –useradd Command to remove a user account Knoppix – deluser Linux - userdel Review week ten lab assignment Managing Users Adding a user to a computer involves several steps before the user can actually log in and perform user operations. Every user that intends to utilize a computer must first gain access to that system, then go through an initialization process found under the user’s home directory. The new user initialization process begins by reading and executing the commands and environmental variables found in the $HOME/.profile file or .bash_profile. Normally, the .profile is run automatically when you log into the system and the user’s environment is set up silently. Once the user is granted access permission to the system, a shell is spawn to allow the user to interact with the system. Review week ten lab assignment Managing Users Display the ~dandrear/.profile When adding a new user account to the system, the administrator assigns the username a user identification number (UID). The UID is used internally by the system to identify each user. Duplicating the UID causes the accounts to share an identity in the system. Review week ten lab assignment Processes The & symbol represents the background process. Once a background process is launched by a terminal session, the process becomes unattached to the terminal that launched it. Background processes are terminated typing kill -9 <pid> Example: simple_script & Once a foreground processis started, it remains in the foreground until it completes, because it remains attached to the terminal. Foreground process by typing Ctl-C Review week ten lab assignment Kernel functions in two ways An autonomous function is the allocation of memory and CPU, which are performed without explicitly requested by a user process. A responsive function is one where resource allocation and process creation and management, are initiated by requests from processes. The daemon processes are started as part of the boot process and run until the system is shut down. Daemon processes can be associated with a systems database applications, network , secure terminal and file transfer, and scheduling tasks Review week ten lab assignment UNIX inetd Daemon The UNIX inetd daemon may start the telnetd to handle a telnet connection. Inetd daemon may start the ftpd to handle an ftp connection. One daemon may start another; the UNIX inetddaemonwill accept a network connection and then start another daemon to handle the connection, based on the type of connection. There are various processes in UNIX that are not owned by a user, but exist to provide services. These processes are often called "daemons.“ The inetdsuperserver runs continuously listening for network connections. This type of daemon is more susceptible to be system breaches. Review week ten lab assignment Linux xinetd daemon The Linusxinetd daemon is a more secure replacement for the inetdsuperserver. The xinetdsuperserver listens for network connections. When a connection is made, it launches a specific daemon and forwards the data from the socket to the daemon’s standard input. Basically, the xinetdsuperserver works on-demand. Review week ten lab assignment Single and Multi-Threaded Processes The implementation of a thread may differ from one operating system to another. Generally, a thread exists within a process. Multiple threads within a single process can co-exist and share the same resources. Review week ten lab assignment Threads compared to Processes Threads exist as subsets of a process. Multiple threads in a single process share memory and other resources. Threads share the same address space. Threads utilize context switching the same as a process. Review week ten lab assignment Single and Multi-Threaded Processes Single threaded process is when a process only performs one task. An embedded system is an example of a single threaded process (BIOS). Multiple threaded process is when a process can perform multiple tasks concurrently without extra overhead needed to create a new process. Word processor is a multiple threaded process. Review week ten lab assignment Kernel Functions The kernel is part of the operating system that allocates machine resources, including memory, disk space, and CPU cycles, to all other programs that run on a computer. The kernel can be responsible for creating the init process. The init process is created through a process called hand-crafted or spontaneous. Review week ten lab assignment fork command Is a command that causes the shell to fork a new process, creating a duplicate of the shell process (sub-shell). exec command The new process attempts to exec the command. If the command is a binary executable program, like a compiled C program, exec succeeds and the system overlays the newly created sub-shell with the executable program. The fork and exec commands are system calls that are executed by the operating system. Review week ten lab assignment Linux Process States Processes go through various process states during their existence. These are transitory statesmanaged by the operating system (OS). The specifics of these process states vary from one OS to another, as well as state names. Waiting (process scheduler - load from secondary storage to main memory) Executing (after a process is assigned a processor by a short – term scheduler, context switch is performed) Stopped (The process has been stopped, usually by receiving a signal. A process that is being debugged can be in a stopped state or another task is executing ) Zombie (This is a halted process for some reason. Still has a task_struct data structure) Review week ten lab assignment Review week ten lab assignment Review week ten lab assignment A zombie process is one that has completed execution but still has an entry in the process table, allowing the process that started it to read its exit status. Remember that a zombie is already dead. Processes marked <defunct> are dead processes (so-called "zombies") Locate a zombie process on cs.franklin.edu Commands: ps -aux ps -aux | awk ‘{ print $8 “ “ $2 } ‘ | grep -w Z Review week ten lab assignment Orphan process is a process whose parent process has terminated or finished. Characteristics of an orphan process: The owner of an orphan process can kill that process. Logging off your terminal will not guarantee termination of your orphan. An orphan process may continue to execute, taking up system resources and slowing the machine down for other users. If you notice slow performance on a machine and you see an orphan process that doesn’t belong to you. Review week ten lab assignment root 9983 927 0 21:37 ? 00:00:00 sshd: [email protected]/* *//0 dandrear 9984 9983 0 21:37 pts/0 00:00:00 -ksh dandrear 10121 10118 0 21:47 pts/0 00:00:00 sort -r dandrear 10120 10118 0 21:47 pts/0 00:00:00 grepdandrear dandrear 10119 10118 0 21:47 pts/0 00:00:00 ps -ef dandrear 10118 9984 0 21:47 pts/0 00:00:00 /bin/ksh ./pid_ppid.sh dandrear Review week ten lab assignment Is there an orphan process listed below? root 9983 927 0 21:37 ? 00:00:00 sshd: [email protected]/* *//0 dandrear 9984 9983 0 21:37 pts/0 00:00:00 -ksh dandrear 10121 10118 0 21:47 pts/0 00:00:00 sort -r dandrear 10120 10118 0 21:47 pts/0 00:00:00 grepdandrear dandrear 10119 10118 0 21:47 pts/0 00:00:00 ps -ef dandrear 10118 9984 0 21:47 pts/0 00:00:00 /bin/ksh ./pid_ppid.sh dandrear Review week ten lab assignment Terminate orphan Processes kill -3 8074 Signal the process with 8074 pid to “quit” kill -1 8074 Signal the process with 8074 pid to “hangup” kill -9 8074 Signal the process with pid 8074 to be “killed” Review week ten lab assignment /etc/rc.d/rc.sysinit This init script performs basic system configuration which includes setting the system clock, hostname, and keyboard mapping; setting up the swap partitions; checking the remaining file system for errors; and turning on the quota management. /etc/rc.d/rc This init script runs the scripts for the services that need to be started when you first bring the system up and that need to be started or stopped when the system goes from single user mode to multiuser mode and back down again. Review week ten lab assignment /etc/rc.d/init.d This init directory contains shell rc scripts and run via symbolic links in the /etc/rc.d/rcn.d directories, where n is the runlevel the system is entering. The following scripts reside in this directory. /etc/rc.d/rc.local This file is executed after the init scripts. Commands can be placed in this file to customize the system. These commands are best suited to execute in the background and after the initialization process completes. Review week ten lab assignment /etc/rc.d/rc1.d This directory contains scripts that start and stop during a specific run level. The following scripts execute during run level one (1): K10cups K25sshd K50netdump K74nscd K86nfslock K91isdn S01sysstat Notice the numbering from 00 to 99. This numbering provides positioning of a script within the whole scheme of execution. Review week ten lab assignment /etc/rc.d/rc1.d K01cmanic -> /etc/init.d/cmanic K01hprsm -> /etc/init.d/hprsm K03rhnsd -> ../init.d/rhnsd K05atd -> ../init.d/atd K05saslauthd -> ../init.d/saslauthd K10cups K10hpasm -> /etc/init.d/hpasm K10psacct -> ../init.d/psacct K15gpm -> ../init.d/gpm-> ../init.d/cups Week ten, eleven, & twelve expected outcomes Upon successful completion of this module, the student will be able to:
  • Manipulate user accounts.
  • Describe how cron is used to invoke repetitive processes.
  • Manipulate process structure including: a) fork and execute b) Initialization process c) Background/foreground d) PS tool
  • Explain basic UNIX security issues.
  • Describe disk and file system structure.
  • Use backup and restore archival operations on a system.
  • Establish network services.
  • Investigate the structure of the LDAP directory using LDAP commands.
  • Next Lab Assignment NFS (Network File System) In UNIX, the file system isn’t visible to the user. The user doesn’t know or have a need to keep track of the physical location of file(s) like other file systems require. The root directory, denoted by a forward slash (/) is the central component of the file system. Other directories can be attached (mounted) to the root directory and utilized. Next Lab Assignment NFS (Network File System) NFS is a file and directory sharing mechanism native to Unix and Linux. NFS is simple to set up. On the server, you make an entry in the /etc/exports file to enable its use by the client. This is called sharing. Next Lab Assignment NFS (Network File System) On the server, enter the following information to allow sharing: /etc/passwd 192.167.99 .0/24 (rw) In order for the client to access the shared directory, the following commands must be input: mount /etc/passwd mount –t nfs –o rw192.167.99.18:/etc/passwd /mnt/nfsdir Next Lab Assignment NFS (Network File System) Many supposed NFS problems are really problems with the firewall. In order for your NFS server to successfully serve NFS shares, its firewall must enable the following: ICMP Type 3 packets Port 111, the Portmap daemon Port 2049, NFS The port(s) assigned to the mountd daemon Next Lab Assignment Samba Sa
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