1. John Carelli, Instructor Kutztown University carelli@kutztown.edu

2. /etc/passwd /etc/shadow NIS NIS+ LDAP
user info – ID, group ID, home dir, shell, …
/etc/shadow
actual password (encrypted)
NIS
network information service (yellow pages)
distribute sys info (user names…) across computers on a network
NIS+
updated version from Sun
eliminate duplication of config data across network
LDAP
Lightweight Directory Access Portocol
industry standard protocol
distribute information across an IP network (name, passwords, etc…)

3. Add A New User Default settings
useradd [-u uid] [-o] [-g group] [-G group [, group, …] [-d home] [-m] [-k template] [-f inactive] [-r] [-p passwd] [-s shell] [-e expire] [-c comment] login
Default settings
useradd -D [-g group] [-b base] [-f inactive] [-e expire] login
useradd –D
to see default settings

4. usermod [-u uid] [-o] [-g group] [-G group [, group, …]
usermod [-u uid] [-o] [-g group] [-G group [, group, …] [-d home] [-m] [-l new_login] [-f inactive] [-r] [-p passwd] [-s shell] [-e expire] [-c comment] login
userdel [-r] login

5. root (superuser)
daemon (system server processes/files)
bin (owns system executable’s and files)
sys (for Distributed File Services, DFS)
lp (printers)
adm (basic system functions)
nobody (default for unprivileged operations)
(more info here)

6. Primary group Secondary groups /etc/group - groups on system
groups command
get a listing
user can change current group with newgrp
groupadd [-g gid] group
to add a new group (root)

7. root
daemon
sys
tty
bin
adm lp
mail
uucp / nuucp
nobody
noaccess

8. backup from one machine label all tapes grandfather / father / son
3 backup cycles (ex: daily, weekly,monthly)
avoids propagating an error
secure backup tapes
keep tapes off-site
backup appropriately
always check restore procedure periodically
develop a tape life cycle

9. activity on filesystem
capacity of dump device
length of “dump window”
amount of redundancy
number of tapes available
how far back you must be able to recover

10. dump / ufsdump (Solaris – unix file system dump)
cpio
packs data on tape more efficiently than tar
skips bad spots on restore (tar dies)
can span tapes
dump / ufsdump (Solaris – unix file system dump)
full vs incremental (0-9)
info saved in /etc/dumpdate
ufsdump N [u] [s length] [d density] [f dump_file]
files_to_dump (files or a mount point)

11. mt [-f tape_device] command
commands
rew - rewind
offl - offline (unload the tape)
status - output status info on tape unit
fsf [count] - forward space “count” files (i.e. jump ahead)
restore [i] [x file_to_restore]
[f tape_device]

12. Linux Device Names (disks)
The first floppy drive is named /dev/fd0.
The second floppy drive is named /dev/fd1.
The first hard disk detected is named /dev/sda.
The second hard disk detected is named /dev/sdb, and so on.
The first SCSI CD-ROM is named /dev/scd0, also known as /dev/sr0.
The partitions on each disk are represented by appending a decimal number to the disk name: sda1 and sda2 represent the first and second partitions of the first SCSI disk drive in your system.

13. Physically add drive
Create entries in /devices and/or /dev
mknod command can do this
format the drive
mkfs (make the file system)
newfs a newer, friendlier, version
Add entry to /etc/fstab (optional)
contains info about how fs should be mounted

14. Record characteristics of a file system
length of a disk block
size and location of inode tables
disk block map and usage information
size of the cylinder groups
other important parameters of the filesystem
more info here:

15. Disk Information Get information about available disks: df command
Disk space usage
df –aTh (more readable format)
lsblk command
useful info about block devices
major/minor numbers, /dev name, mount point, …
lsusb command (for usb devices)
fdisk –l device
ex: fdisk –l /dev/sda (need to be root)

16. mount [-r] [device] <directory>
uses /etc/fstab to get disk info
-r for read only
mount -t type [device] <directory>
specify the type of device
mount [-f filesystem_types]
“fake” – don’t actually mount anything
see what mount is trying to do, or
add entries to /etc/mtab (for previously mounted devices)
mountall
called during boot process

17. umount <filesystem>
umountall

18. Who is using a filesystem?
fuser [-u] [-k] <device> -u for user -k kills the process using the device! -v is verbose
Checking a filesystem
fsck
careful with this one!
[-p] [-n] [-y] [-F filesystem_type] [raw_device]

19. fixes damaged or inconsistent inodes
unreferenced inodes
large link counts
unused data blocks not recorded in block maps
data blocks listed as free but also used in a file
incorrect summary info in superblock

20. Set up user quotas (limits on disk space usage)
rq in /etc/fstab (normally rw)
create a quotas file in the affected filesystem
edquota [-p prototype_user] <user>
quota

21. Network File System - allows access over a network (looks like local storage) - runs on top of RPC protocol (Remote Procedure Call)
Daemons
nfsd, automountd, statd, lockd, nfslogd
more info here
/etc/exports
- specifies exported file systems and hosts permitted to access them

22. Loading and initialization of kernel
Device detection and configuration
Creation of system processes
Operator intervention (manual boot only)
Execution of startup scripts (by init)
Multiuser operation (init spawns getty process)

23. Also known as run levels
 0 system is completely shut down
 1 single-user mode (administration)
 2 multi-user mode without NFS (networking)
 3 full multi-user mode with networking
 4 unused
 5 full multi-user mode with networking and X11 (GUI)
 6 reboot
startup scripts defined in /etc/rc#.d
commands in /etc/rc.local will execute at the end of the boot process

24. setting the name of the computer
setting the time zone
checking the disks with fsck
mounting the system’s disks
removing old files in /tmp
configuring network interfaces
starting up daemons and network services

25. logs shutdown
kills nonessential processes
executes sync
waits for filesystem writes to complete
halts the kernel

26. shutdown [TIME] [message]
halt
reboot [-p] (-p is poweroff)
init <run_level>
generally run by kernel
or, restart with the given runlevel

27. flushes cached superblocks to disk
flushes modified inodes and cached data blocks

28. Updates to system files
Correct errors or provide security fix
patch

29. CD
Download source code
Download package

30. yum
apt-get

31. Configuration file: yum.conf
yum install
<packageName>
Install package and dependency packages
yum update [<packageName>]
Without package name, updates all installed packages
yum check-update
Lists available updates for installed packages
yum clean all
Removes all header files used for resolving dependencies and cached packages
yum list available
Lists all available packages
yum search <word>
Searches for word in package description, summary, packager, and name
Groups of packages
yum grouplist
yum groupinfo
Yumdownloader
Configuration file: yum.conf

32. apt-get update
Update local package list
apt-get check
Check status of local dependency tree
apt-get install <package>
apt-get remove <package>
apt-get upgrade
Upgrade all packages on the system that don’t require any new packages
apt-get dist-upgrade
Upgrade all packages on the system and install any new packages necessary

33. A background process that performs a specific function or system-related task

34. SYSLOGD - system logging
Syslog – standardized system for managing system log files
programs write to the special file /dev/log
syslogd reads messages from this file
consults configuration file syslog.conf
dispatches each message to appropriate destination
sysadmin should back up and maintain log files
Common Log Files
/var/log/messages
/var/log/auth.log
/var/log/kern.log
/var/log/cron.log
/var/log/maillog
/var/log/httpd
/var/log/boot.log
/var/log/mysqld.log
/var/log/utmp
/var/log/wtmp
/var/log/yum.log

35. SYSLOGD – facility names
kern
user
mail
daemon
auth
lpr
uucp
cron
mark
local0-7
syslog
authpriv
ftp
news
 *
The kernel
User processes (default)
sendmail and other mail-related software System daemons
Security/authorization related commands The BSD line printer spooling system Reserved for UUCP (doesn’t use it)
The cron daemon
Timestamps generated at regular intervals Local messages
syslogd internal messages Private authorization messages The ftp daemon, ftpd
news service
All facilities except mark

36. Panic situations (can also use panic) Urgent situations
Critical conditions
Other error conditions (can also use error) Warning messages (can also use warning) Things that might merit investigation Information messages
For debugging only no priority
all priorities
emerg
alert
crit
err
warn
notice
info
debug
none
 *

37. a daemon that manages other daemons
Consults config file to determine which network ports to listen to
Uses /etc/services or portmap daemon to map service names to port numbers

38. time 1 service name 2 type of socket service uses (stream or dgram)
3 communication protocol service uses (tcp or udp)
4 wait: service can process multiple requests at one
time
nowait - fork a new copy of daemon for each request
5 username under which daemon should run
6 fully qualified pathname of the daemon and its
command-line arguments

39. a daemon that manages port assignments for daemons that use RPC (Remote Procedure Call)
Analogous to a function call across machines

40. Report on virtual memory usage
Two arguments
number of seconds between measuring and reporting values
number of times to measure and report values
Report
First line will be average values since last system reboot
Other lines represents current values
man vmstat

41. Report on network connection information
Common options
netstat –v
netstat –nt
netstat –nl
netstat –I
netstat –rn
netstat -s