CIT 500: IT Fundamentals

1. CIT 500: IT Fundamentals Packages and Filesystems

2. Topics • Packages • The software installation problem • UNIX package managers • Dependencies • Advanced package managers • Filesystems • Filesystem types • Integrity and repair • Permissions and attributes

3. Software Installation • Customization Select options like language. Select file set. • Install new files in appropriate locations. • Modify existing configuration files. • Make software available to user. Shell configuration (PATH, etc.) GUI configuration (menu, icons, etc.)

4. What’s the problem? What prerequisites does your software have? What prereqs do your prereq packages have? How do you handle conflicts? What if two programs install/modify same file? Does your install work on every type of computer? How do you handle upgrades? What if user has customized configuration? What if ownerships/permissions have changed? What if user needs old and new versions? How do you uninstall software?

5. Package Manager Features • Build management. • Dependency tracking. • Querying. • Reversibility. • Verification. • Version control.

6. UNIX Package Management Systems deb: Debian system uses dpkg and APT. pkgadd: Solaris packaging system. portage: Gentoo uses with emerge. ports: BSD ports system. RPM: Redhat packaging system. tgz: Tarballs used by Slackware.

7. dpkg Debian package system • Original version created in 1993 • APT introduced in 1998 Distributions • Debian • Knoppix • Linspire • MEPIS • Ubuntu dpkg on other OS • Fink on MacOS X

8. RPM RPM Package Manager • Originally stood for Red Hat Package Manager • Came with Red Hat Linux 2.0 in 1995. Distributions • Red Hat • Red Hat Enterprise Linux (also CentOS) • Fedora • Mandriva • SUSE RPMs are not compatible between distributions. RPM on other OS • AIX • Novell Netware

9. RPM Package Names <name>-<version>-<release>.<arch>.rpm Name: name of the software package. Version: version of the software package. Release: release version of the RPM. Arch: architecture (i386, noarch, ppc, etc.) If Arch is src, RPM contains source code for building the package.

10. RPM Package Contents Identification Identifies package and RPM version. Signature Checksum and digital signature. Header Package and version information. Specifies dependencies on other packages. Payload Actual files to install. Stored as cpio archive compressed with gzip. Use rpm2cpio to obtain cpio archive.

11. Using RPM • Install • Uninstall • Upgrade • Query • Verify

12. Installing a Package • Check the package and the files it wants to install. • Perform preinstallation tasks. • Uncompress the files and copy them in the proper locations • Perform post-processing tasks • Update the RPM Database > rpm -ivh foo-1.0-1.i386.rpm Preparing... ########################################### [100%] 1:foo ########################################### [100%]

13. Upgrading a Package Uninstall + install, retaining configuration files. Will install a package if no older version. Will remove all older versions. Typically use –U instead of –i for installs too. > rpm -Uvh foo-1.0-1.i386.rpm Preparing... ########################################### [100%] 1:foo ########################################### [100%]

14. Uninstalling a Package Completely removes package from system. > rpm -e foo-1.0-1 > rpm –q foo package foo is not installed.

15. Dependencies Prevent install/removal if unfulfilled. # rpm -e setup error: Failed dependencies: setup is needed by (installed) basesystem-8.0-1 setup >= 2.0.3 is needed by (installed) initscripts-6.95-1 setup >= 2.5.4-1 is needed by (installed) filesystem-2.1.6-5 setup is needed by (installed) xinetd-2.3.7-2 setup is needed by (installed) dump-0.4b28-4 # rpm -q setup setup-2.5.20-1

16. RPM Database Tracks global package information: • List of all packages • Dependencies between packages For each package, stores: • Name, version, and architecture (-q) • Information fields, including description (-qi) • List of files (-ql), config files (-qc), doc files (-qd) • Date of install

17. Querying the RPM Database # rpm -q telnet telnet-0.17-31.EL4.3 # rpm -ql telnet /usr/bin/telnet /usr/share/man/man1/telnet.1.gz # rpm -qi telnet Name : telnet Relocations: (not) Version : 0.17 Vendor: CentOS Release : 31.EL4.3 Build Date: Tue 14 Jun 2005 Install Date: Sat 11 Feb 2006 Build Host: build5 Group : Applications/Internet Src RPM: telnet-0.17.src.rpm Size : 87254 License: BSD Signature : DSA/SHA1, Tue 14 Jun 2005, Key ID a53d0bab443e1821 Packager : Johnny Hughes <johnny@centos.org> Summary : Client program for telnet remote login protocol. Description : Telnet is a popular protocol for logging into remote systems over the Internet. The telnet package provides a command line telnet client.

18. Querying the RPM Database # rpm -qc bash /etc/skel/.bash_logout /etc/skel/.bash_profile /etc/skel/.bashrc # rpm -qd sendmail /usr/share/man/man1/mailq.sendmail.1.gz /usr/share/man/man1/newaliases.sendmail.1.gz /usr/share/man/man5/aliases.sendmail.5.gz /usr/share/man/man8/mailstats.8.gz /usr/share/man/man8/makemap.8.gz /usr/share/man/man8/praliases.8.gz /usr/share/man/man8/rmail.8.gz /usr/share/man/man8/sendmail.sendmail.8.gz /usr/share/man/man8/smrsh.8.gz

19. Searching all Packages # rpm -qa | grep telnet telnet-0.17-31.EL4.3 # rpm -qa | grep py python-2.3.4-14.1 pyOpenSSL-0.6-1.p23 rpm-python-4.3.3-11_nonptl pygtk2-2.4.0-1 python-devel-2.3.4-14.1 python-ldap-2.0.1-2 pyxf86config-0.3.19-1 libxml2-python-2.6.16-6 python-elementtree-1.2.6-4 python-sqlite-1.1.6-1 dbus-python-0.22-12.EL.5 pyparted-1.6.8-2 python-urlgrabber-2.9.6-2

20. Searching all Packages Find recently installed packages rpm -qa --last Find packages that are disk hogs rpm -qa --qf "%{size} %{name}\n" | sort –n The --qf (queryformat) option can print arch, name, size, version, distribution, etc.

21. Querying Files and Packages Find which package a file belongs to: # rpm -qf /usr/bin/telnet telnet-0.17-31.EL4.3 # rpm -qf /etc/security/limits.conf pam-0.77-66.11 Querying packages Add –p to any query to apply it to a .rpm file instead of to an installed package.

22. Verifying Packages Verifying a package returns nothing if ok # rpm -V telnet Returns errors if package has problems # rpm -V telnet-server missing c /etc/xinetd.d/telnet missing /usr/sbin/in.telnetd missing d /usr/share/man/man5/issue.5.gz

23. RPM Options Specify multiple RPMs at once. RPM will re-order installs to resolve dependencies. Prefix: install in new location. rpm --prefix /usr/local –Uvh *.rpm Oldpackage: revert to an older version rpm --oldpackage –Uvh foo-0.9-2.i386.rpm Forcing install, upgrade, or removal --force allows overwriting of files/packages. --nodeps allows install w/o dependency check.

24. Dependency Resolution Higher level tools handle dependencies up2date, yum, yast, urpmi Automatic resolution + downloading. 1. Find dependencies in RPM headers. 2. Download dependencies, check their headers. 3. Repeat. 4. Install after all RPMs downloaded.

25. Yellow Dog Updater Modified • Rewrite of YUP from Yellow Dog Linux. • Used by many RPM-based distributions. Automatically syncs repo metadata. • Prevents problems arising from out of data package information on local system. • Wastes time when local data up to date.

26. Yum Installs yum install pkg: finds specified package, downloads it, and installs it. yum remove pkg: remove the specified package from the system. yum update <pkg>: updates specified package or updates all packages if no package specified.

27. yum list <option> <pkgspec> Options: available: list packages available to be installed. installed: list installed packages like rpm –qa. extras: lists installed packages that are not available on any currently configured repo. recent: lists packages added to repositories in last 7 days. updates: lists updates for any installed packages. Package Specifications: bash bash-3.10 \*sh \*.i386

28. Yum Commands check-update: lists updates, returns 100 if any updates available. clean: removes yum cache files. deplist: list all dependencies for a package. info: list package data like rpm –qi yum provides: find which package provides the specified command, i.e. yum provides \*bin/ls. yum search: lists packages whose name, summary, description, or URL matches the specified search term.

29. Package Sources Sources • Local files (CD/DVD or hard disk) • Red Hat Network commercial sites for RHEL • CentOS network official mirrors for CentOS • Unofficial network repositories like RPMforge Source configuration up2date: /etc/sysconfig/rhn/sources yum: /etc/yum.conf, /etc/yum/repos.d

30. Finding RPMs • The Red Hat Enterprise Linux CD-ROMs • The Red Hat Errata Page available at http://www.redhat.com/apps/support/errata/ • A Red Hat FTP Mirror Site available at http://www.redhat.com/download/mirror.html • Dag RPM Repository at http://dag.wieers.com/home-made/apt/ • Search for RPMs at www.rpmfind.net. • Search for RPMs at rpm.pbone.net.

31. Filesystem Types Disk-based Filesystems • Filesystems designed to store files to a fixed or removable permanent storage device. Flash Filesystems • Flash can only be written to 1000s of times. • Re-arrange block usage to avoid writing too many times to any one block on flash. Journaling Filesystems • Modify how writes are done to provide greater data integrity in case of a system crash.

32. Filesystem Tree Structure / bin boot tmp usr var bin lib X11R6 ls grub less vmlinuz bin lib zip menu.lst xclock xterm

33. Journaling Filesystems Problem: writing to file involves many disk writes • Modify inode to change file size • (potentially) Add new data block to used block map • (potentially) Add pointer to new data block • Write to new data block Journaling filesystems perform writes by: • Write blocks to journal. • Wait for write to be committed to journal. • Write blocks to filesystem. • Discard blocks from journal.

34. Common Disk-based Filesystems Extended Filesystem • ext2: first full featured UNIX fs for Linux in 1993 • Recommended use: USB + other solid state drives. • ext3: ext2 + journalling • ext4: faster version of ext3 with larger file support Microsoft Filesystems • FAT: inefficient disk usage, slow, 8+3 filenames • 16- and 32-bit versions used on flash storage • NTFS: modern filesystem, many versions • Supports long + old 8+3 filenames for compatibility

35. Ext2 Disk Data Structures

36. Inode Block Addressing

37. Creating a Filesystem Select a disk partition to create filesystem on fdisk –l /dev/sda will list partitions on 1st disk fdisk –l /dev/sdb will list partitions on 2nd disk, etc. Run mke2fs –v /dev/sda2 Creates ext2 filesystem on 2nd partition of 1st disk Wipes any data already existing on that filesystem Add a –j option to create an ext3 journaling fs.

38. Mounting a Filesystem • Create a mountpoint mkdir -p /stor/video • Mount filesystem on chosen directory mount -t ext3 /dev/sda2 /stor/video • Use filesystem • Unmount filesystem when done umount /dev/sda2 Happens automatically at reboot or shutdown

39. Automatic Mounting Filesystems in /etc/fstab are mounted on boot. Use mount to see current mounted filesystems. # /etc/fstab: static file system information. # # <device> <mnt pt> <type> <options> <dump> <pass> proc /proc proc defaults 0 0 /dev/sda1 / ext3 defaults 0 1 /dev/sda2 none swap sw 0 0 /dev/sda3 /home ext3 defaults 0 1 /dev/sdb1 /backup ext3 defaults 0 0

40. Checking Filesystem Integrity fsck utility performs consistency checks • Are used blocks actually used? • Do inodes point to any unused blocks? • Are used inodes pointed to by directory entries? and repairs inconsistencies if • Sysadmin enters ‘y’ in interactive mode. • Sysadmin uses ‘-y’ argument to do all repairs. Run fsck with unmounted partition as arg: fsck –y /dev/sda2

41. Access Control: Permissions Read • You can read the file with cat, more, etc. Write • You can modify the file with vi, OpenOffice, etc. Execute • You can run the file if it’s a program.

42. Three Sets of Permissions

43. Access Control Commands Changing File Access Privileges chmod [options] octal-mode file chmod [options] symbolic file

44. POSIX ACLs Specify individual groups and users. Basic ACL user/group refers to owner. POSIX ACLs allow specifying users + groups. To add/modify permissions for a user: setfacl –m u:username:rw- filename To add/modify permissions for a group: setfacl –m g:groupname:rw- filename

45. ACL Examples $ getfacl acltest # file: acltest # owner: waldenj # group: waldenj user::rw- group::r-- other::r-- $ setfacl -m u:trutat:rw- acltest $ getfacl acltest # file: acltest # owner: waldenj # group: waldenj user::rw- user:trutat:rw- group::r-- mask::rw- other::r--

46. File Attributes Attributes extend file permissions: a: append-only (only root can set) i: immutable (read-only, only root can set) s: safe-delete (overwrite, not supported yet) Use lsattr to view attributes. Most files do not have any attributes set. Use chattr to set attributes. chattr +i /boot/vmlinuz*

47. References • Syed Mansoor Sarwar, Robert Koretsky, Syed Ageel Sarwar, UNIX: The Textbook, 2nd edition, Addison-Wesley, 2004. • Nicholas Wells, The Complete Guide to Linux System Administration, Thomson Course Technology, 2005.