CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 1 of 7
--------------------------------------------------------------------------
1. Basic terms:
-----------------------------------------------------------------------
| block | Minimum size of read/write to disk or tape. |
–---------------------------------------------------------------------—
| daemon | Background task owned by init (process 1). |
–---------------------------------------------------------------------—
| device filename | Pathname of a device -- usually in /dev. |
–---------------------------------------------------------------------—
| device | A physical computer hardware component. |
–---------------------------------------------------------------------—
| environment | The set of variable values used by a shell. |
–---------------------------------------------------------------------—
| filesystem | A data structure: superblock, inodes, data. |
–---------------------------------------------------------------------—
| fork | Create a process, synonym: spawn. |
–---------------------------------------------------------------------—
| kernel | Always in memory, allocates and controls |
–---------------------------------------------------------------------—
| login shell | Spawned when you log in. Spawns other processes.|
-–------------------------------------------------------------------—
| mount (a device) | Action that makes a device or filesystem usable.|
–---------------------------------------------------------------------—
| process | A program running in memory. |
–---------------------------------------------------------------------—
| root filesystem | A required filesystem that mounts all others. |
–---------------------------------------------------------------------—
| run level | Access permissions of a process. |
–---------------------------------------------------------------------—
| signal | A numeric value sent to a process via interrupt.|
–---------------------------------------------------------------------—
| spawn | Create a process, synonym: fork. |
–---------------------------------------------------------------------—
| system console | Main system terminal, usual destination/stderr. |
–---------------------------------------------------------------------—
| disk partition | A portion or slice of a disk - data or swap. |
–---------------------------------------------------------------------—
| X server | provides display for X applications. |
-----------------------------------------------------------------------
2. How is the System Administrator (superuser, root) different?
----------------------------------------------------------------------
| Some commands are restricted to superuser-only. |
–--------------------------------------------------------------------—
| Read and write file access permissions do not affect the superuser.|
----------------------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 2 of 7
--------------------------------------------------------------------------
3. How do you obtain superuser priviledges?
-------------------------------------------------------------------------
| It is automatic when running in single-user mode. |
–-----------------------------------------------------------------------—
| Log in as root. |
–-----------------------------------------------------------------------—
| su (substitute user) to root. |
–-----------------------------------------------------------------------—
| The sudo utility is configurable to give limited superuser priviledge.|
-------------------------------------------------------------------------
4. Why would a system administrator use su to become anyone other than
root?
-----------------------------------------------------------------------
| To preserve individual and group ownership of files. -- Files |
| created by root are owned by root. For example, if you create |
| payroll files as superuser, then the accounting group would be |
| unable to access them. |
-----------------------------------------------------------------------
5. How does single-user mode differ from multiuser mode?
----------------------------------------------------------------------
| Only the system console is enabled. |
–--------------------------------------------------------------------—
| Not all file systems are necessarily mounted. |
–--------------------------------------------------------------------—
| Single user mode is necessary for many maintenance tasks. |
–--------------------------------------------------------------------—
| You will need to execute sync manually to write changes to disk. |
----------------------------------------------------------------------
6. Where are System Administrator tools usually stored.
----------------------
| /sbin | /usr/sbin |
----------------------
7. How many inodes does a file have? What happens when you add a hard
link to a file? What happens when you add a symbolic link?
-------------------------------------------------------------------------
| 1 inode per file |
–-----------------------------------------------------------------------—
| hard link: a additonal reference to an inode in a single filesystem.|
–-----------------------------------------------------------------------—
| each filesystem has only one set of inodes. |
–-----------------------------------------------------------------------—
| symbolic links do not share an inode. |
–-----------------------------------------------------------------------—
| directories may also have symbolic links. |
-------------------------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 3 of 7
--------------------------------------------------------------------------
8. What are the differences between a raw device and a block device?
------------------------------------------------------
raw: | direct i/o no buffering |
ex:fsck –----------------------------------------------------—
| 1 call, 1 r/w |
–----------------------------------------------------—
| device dependent restrictions on i/o |
------------------------------------------------------
------------------------------------------------------
Block: | may perform random r/w |
ex:normal i/o –----------------------------------------------------—
| specific block size |
–----------------------------------------------------—
| one block at a time |
–----------------------------------------------------—
| whole blocks |
–----------------------------------------------------—
| can have a file system mounted on it |
–----------------------------------------------------—
| may have the kernel buffer as its input and output |
–----------------------------------------------------—
| appears to o/s as a series of blocks |
------------------------------------------------------
9. How do you bring the system down?
-------------------------------------------------------------------------
| /sbin/shutdown -t3 -rf The system will reboot in 3 minutes. |
–-----------------------------------------------------------------------—
| /sbin/shutdown -h 09:30 The system will halt at 09:30 |
-------------------------------------------------------------------------
10. What are some important files?
-------------------------------------------------------------------------
| /dev/null | used to suppress output |
–-----------------------------------------------------------------------—
| cron.allow, cron.deny | restrict access to cron |
–-----------------------------------------------------------------------—
| at.allow, at.deny | restrict access to at |
–-----------------------------------------------------------------------—
| /etc/group | allows group access to files |
–-----------------------------------------------------------------------—
| /etc/mtab | lists mounted devices |
–-----------------------------------------------------------------------—
| /etc/motd | message of the day |
–-----------------------------------------------------------------------—
| /etc/pam.conf, /etc/pam.d/* | Plug and play authentication |
–-----------------------------------------------------------------------—
| /etc/passwd | passwords |
–-----------------------------------------------------------------------—
| /etc/profile | default bourne and Z shell config. |
–-----------------------------------------------------------------------—
| /etc/fstab | mount list on boot / fsck |
–-----------------------------------------------------------------------—
| /vmlinuz | standard name for linux kernel |
-------------------------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 4 of 7
--------------------------------------------------------------------------
11. How often, and how much should you backup?
-------------------------------------------------------------------------
| The more people on the system, the more often you should backup. |
–-----------------------------------------------------------------------—
| The book recommends a partial backup several times a day. |
–-----------------------------------------------------------------------—
| The book recommends a full backup several times a week. |
–-----------------------------------------------------------------------—
| It is a good idea to have offsite copies of backups. |
-------------------------------------------------------------------------
12. What programs can you use to perform backups?
------------------------------------------------------------
| tar | 'tape archive' | very common |
–----------------------------------------------------------—
| cpio | 'copy in-out' | accepts piped input |
–----------------------------------------------------------—
| afio | | can selectively compress |
–----------------------------------------------------------—
| tapir | | gui - stores relative/dir |
------------------------------------------------------------
13. How do you schedule tasks with crontab?
----------------------------------------------------
| crontab submits commands to cron |
–--------------------------------------------------—
| - Minute Hour MonthDay Month Weekday command |
–--------------------------------------------------—
| - 1 1 * * * save |
–--------------------------------------------------—
| - 0 11 4 * mon-wed save |
----------------------------------------------------
12. How do you schedule tasks with at?
-----------------------------------------
| at runs things on a per-job basis |
–---------------------------------------—
| at 1 am Jul 31 save |
-----------------------------------------
13. How do you get information to users?
-------------------------------------------------------------------------
| wall | writes to all terminals that have users logged in. |
–-----------------------------------------------------------------------—
| write, talk | communicates to individual terminals |
–-----------------------------------------------------------------------—
| Mail | goes to individuals, or lists |
–-----------------------------------------------------------------------—
| The Web | the world wide web |
–-----------------------------------------------------------------------—
| motd | when users log on, they see the message of the day. |
–-----------------------------------------------------------------------—
| news | selectively subscribed to by users. |
-------------------------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 5 of 7
--------------------------------------------------------------------------
14. How do you add and remove user accounts?
-------------------------------------------------------------------------
| useradd | command line |
–-----------------------------------------------------------------------—
| adduser | interactive |
–-----------------------------------------------------------------------—
| xusermgr | gui |
–-----------------------------------------------------------------------—
| userdel | deletes a user account, and his/her directories |
-------------------------------------------------------------------------
15. How do you monitor systems usage?
-------------------------------------------------------------------------
| Watch for growing files such as log files and temporary files. |
–-----------------------------------------------------------------------—
| df - report on free disk space |
–--------------------˜----------˜-----------------˜---------------------—
| ps -l long format | -A/e all | -f full listing | -u username |
–-------------------------------™-----------------™---------------------—
| top - (linux) display cpu processes - interactive interface |
| repetitive update formatted directly from kernel information.. |
-------------------------------------------------------------------------
16. How do you identify what processes a user is running?
---------------------------------------------------------
| w - show who is logged on and what they are doing. |
–-------------------------------------------------------—
| ps -efu username |
–-------------------------------------------------------—
| ps -auw | grep username | grep -v grep |
–-------------------------------------------------------—
| ps -U |
–-------------------------------------------------------—
| find the user's UID from field 3 of /etc/passwd |
---------------------------------------------------------
17. Some useful utilities:
-------------------------------------------------------
| chsh change a user's shell |
–-----------------------------------------------------—
| clear clears the screen |
–-----------------------------------------------------—
| reset resets default screen characteristics |
–-----------------------------------------------------—
| dmesg displays recent log messages |
–-----------------------------------------------------—
| ping tests network connections |
–-----------------------------------------------------—
| setserial configures a serial port |
–-----------------------------------------------------—
| uuname displays information about the system. |
-------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 6 of 7
--------------------------------------------------------------------------
15. How do you mount and unmount filesystems?
-------------------------------------------------------------------------
| The directory you mount them in must exist. |
–-----------------------------------------------------------------------—
| mount will fill in some missing arguments with info from /etc/fstab. |
–-----------------------------------------------------------------------—
| When you mount a filesystem in a directory that has files in it, |
| they 'appear to disappear' afterwords. They are inaccessable |
| because the directory inode now points elsewhere. When the |
| filesystem is unmounted, they will 'reappear'. |
–-------˜----------------------------------------------------------------—
| mount | filesystem-type | device | directory |
–-----------------------------------------------------------------------—
| mount -t msdos /dev/fd0 /mnt/floppy |
–-----------------------------------------------------------------------—
| mount -t msdos /dev/hda1 /mnt/c: |
–-----------------------------------------------------------------------—
| mount -t ext2 /dev/hda3 /usr |
-------------------------------------------------------------------------
16.Where would a system administrator find primary technical
support for unix? Who is the primary technical supporter of
unix and linux?
-------------------------------------------------------------------------
| AT&T SCO Hewlett Packard Digital Sun Microsystems |
–-----------------------------------------------------------------------—
| Red Hat Caldera Slackware Free BSD SuSE |
–-----------------------------------------------------------------------—
| www.linux.org www.redhat.com www.li.org www.linuxjournal.com |
–-----------------------------------------------------------------------—
| comp.os.linux.announce comp.os.linux.answers comp.os.linux.setup |
–-----------------------------------------------------------------------—
| comp.os.linux.hardware comp.os.linux.networking comp.os.linux.x |
–-----------------------------------------------------------------------—
| comp.os.linux.development.apps comp.os.linux.development.system |
–-----------------------------------------------------------------------—
| comp.os.linux.advocacy comp.os.linux.misc |
–-----------------------------------------------------------------------—
| comp.unix.* in netnews |
–-----------------------------------------------------------------------—
| plug - Philadelphia Linux Users Group: linux-list@ccil.org |
| (Chris Fearnley) send mail here to join: |
| linux-list-request@locke.ccil.org |
| with a subject of SUBSCRIBE |
-------------------------------------------------------------------------
17. What is the command to start to upgrade UNIX?
----------------------------------------------------------------------
| It depends on what version. Some versions upgrade incrementally, |
| even over the internet. (debian) Others must be reinstalled |
| from scratch (slackware). Installation programs are particular to |
| the distribution. |
----------------------------------------------------------------------
CISC 131.84 Introduction to UNIX (Red Hat Linux)
ADMIN QUESTION SET Page 7 of 7
--------------------------------------------------------------------------
18. How do you set default group and permissions for files as you
create or modify them?
--------------------------------------------------
| umask takes the complement of the permissions | |
–------------------------------------------------—
| umask 777 (no permissions) |
--------------------------------------------------
19. How can you identify the userid of another user on your system?
-----------------------------------------------
| grep '^username:' /etc/passwd | cut -d: -f3 |
-----------------------------------------------
20. What steps does a system administrator do if a user cannot login?
-------------------------------------------------
| confirm old is not working by trying to login |
–-----------------------------------------------—
| Check the terminal by logging on as yourself. |
–-----------------------------------------------—
| make sure the user's HOME dir exists |
–-----------------------------------------------—
| make sure the user owns his HOME directory. |
–-----------------------------------------------—
| verify the entry in /etc/passwd. |
–-----------------------------------------------—
| if it fails, logon as root |
| and change the password with: passwd username |
-------------------------------------------------
21. How do you create a file that belongs to a specific group?
----------------------------------------------------------------
| chgrp groupname filename -- after the file exists |
–--------------------------------------------------------------—
or: | Become a member of that specific group and then create a file|
----------------------------------------------------------------