Administrative Advice for UNIX
Contents
1. usr spoolspooling directory for line printers wucp 1C etc and whose sub directories should be compacted as described above 14 ALLOCATING RESOURCES TO USERS A prospective user should obtain connect time and file space authorization through appropriate channels Once this is done the user should apply for a login by providing the following information to the system administrator e User s name e Suggested login name not more than 8 characters beginning with a lower case letter e Relationships to other users this influences the choice of the file system e Estimate of required file space this also influences the choice of the file system Users should be forced to have passwords not more than 8 characters long but more than 5 and not in Webster s Unabridged passwd 5 explains how to do that 15 THE MATTER OF ACCOUNTING AND USAGE You should run the accounting programs even if you do not bill for service Otherwise your users habits especially bad habits will be a mystery to you Accounting information can also help you find performance bottlenecks unused logins bad phone lines etc 16 DIAL LINE UTILIZATION If prime time dial line utilization gets much over 70 users will start to encounter busy signals when dialing in This in turn will lead to line hogging The only solutions are to get a larger another machine or to get rid of users Manual policing will help some but a2. Preventive maintenance of disk drives is very important Make sure that the Customer Engineers who service your hardware see the error logging printouts and console error messages produced by UNIX and that they understand them Disk failure can ruin a UNIX file system The only defense is to make a complete daily file backup See Protecting User Files above Many administrators believe the the RP04 disk drives fail more often than RP06s and take longer to fix e Dial Ports In this area as well as in the area of synchronous data interfaces there is room for finger pointing among all your vendors Check for obvious things Is the system in multi user mode Is the etc inittab file OK Are any cables loose both ends In some telephone offices trunk hunting is based on 10 number groups Hunting between such groups can fail independently of anything else The possibilities for trouble are many The decision table below attempts to describe some alternatives it is meant primarily for users of DH11 DZ11 asynchronous devices If you are unfamiliar with the format vertical Rule 3 reads If line rings and ring light shows and computer does not answer and switching the modem solves the problem then it is likely to be a telephone company problem also busy out that line e Early experience with the DZ11 has been poor Several different problems have cropped up including bad line units and a
3. breaking the system but you can usually detect that they have done so The following command will mail to root a list of all set user ID programs owned by root super user find user root perm 4100 exec ls 1 mail root Any surprises in root s mail should be investigated Related advice e Change the super user password regularly Don t pick obvious passwords choose 6 to 8 character nonsense strings that combine alphabetics with digits or special characters e If you have dial ports and do not require passwords you are courting trouble e The chroot 1M ans su 1 commands are inherently dangerous as are group passwords consider removing them from production systems e Login directories profile files and files in bin usr bin lbin and etc that are writable by others than their respective owners are security weak spots police your system regularly against them e Remember no time sharing system with dial ports is really secure Don t keep top secret stuff on the system 21 COMMUNICATING WITH YOUR USERS The directory usr news and the news 1 command are provided as a way to get brief announcements to your users More pressing items one liners can be entered in the etc motd message of the day file motd and new to the user news are announced at login time To reach users who are already logged in use the wall 1M write all command Don t use wall while logged in
4. as super user except in emergencies The usr news directory should be cleaned out every few weeks so that nothing older than say three months is ever found there The motd file should be cleaned out daily We have found that on most systems a file in usr news will reach 50 of the users within a day and over 80 of the users within a week 22 TROUBLESHOOTING It would be easy to write a book on this topic The following are some of the key items a Dealing with the hardware service contractor e Before you take out a hardware service contract with DEC or with someone else be sure that the contractor agrees to get along with the UNIX software It s the hardware says you It s the software says the hardware service contractor e Keep on top of problems For instance DEC has a problem aging priority scheme Find out about any such scheme that your contractor may have and make them prove that it is being followed Remember that an unreported problem is getting no priority at all If a problem persists escalate it up your contractor s local management chain it may also be effective to complain to your contractor s sales representative e If you are serious about service to your users you should have an extended period service contract e g 16 hours day 6 days week Arrange for preventive maintenance non critical repair and add on installation work to be done before or after prime time e If you have a se
5. because of file system indirection A UNIX user once complained that it took the system ten minutes to complete the login process it turned out that his login directory was 25K bytes long and the login program spent that time fruitlessly looking for a non existent profile file A large usr mail or usr spool uucp directory can also really slow the system down The following will ferret out such directories find type d size 10 print Removing files from directories does not make the directories get smaller the empty directory entries are available for reuse The following will compact usr mail or any other directory mv usr mail usr omail mkdir usr mail chmod 777 usr mail cd usr omail find print cpio plm mail cd rm rf omail 12 ADMINISTRATIVE USE OF CRON The program cron 1M is useful in the administration of the system it can be used to e Turn off the programs in directory usr games during prime time e Run programs off hours accounting file system administration long running user written shell procedures using the su 1 command for example su userx userx_shell arg 6 Administrative Advice for UNIX 13 WATCH OUT FOR FILES AND DIRECTORIES THAT GROW e Accounting files usr adm wtmplogin information usr adm pacctprocess accounting gets big quickly e Other files Jusr lib cronlogstatus log of commands executed by cron 1M
6. day free counts should be maintained e The file system containing tmp temporary files 16 user system 1 500 free blocks 40 user system 3 000 free blocks e The file system containing usr 3 000 to 6 000 free blocks depending on load e Other user file systems 6 to 10 free depending on user habits 3 000 blocks minimum This brings up an associated problem how big should file systems be Our preference is to set aside space on each drive for a copy of root swap and use the rest of the pack for a single file system However if you have user groups that fight over disk space it may be better to split them up arbitrarily i e divide a pack into more than one file system Warning if you set up different disk drives with differing cylinder partitions between file systems it will probably lead to an operations goof someday 4 A VERY FEW WORDS ABOUT SYSTEM TUNING e As shipped UNIX has no programs with the text bit mode set see chmod 1 The top contenders for the t bit are nroff and troff followed generally by the larger phases of the C compiler including the assembler and loader The bit is only meaningful with pure text programs d 1 options i or n Don t overdo it and keep bit programs in the root file system e File system reorganization described below can help throughput but at the expense of down time If you do it when your users are all asleep it can help e If you use normal shu
7. no no no Blocks per record are cut to 22 without separate I D space We strongly recommend the spare disk drive as explained in Section 5 above the speed and convenience of volcopy are by no means the only advantage of a spare drive 9 CONTROLLING DISK USAGE If your UNIX system is a success you will soon run out of disk space e During the considerable delay before you can get more drives you will need to control usage Try to maintain the start of day counts recommended above Watch usage during the day by executing the df command regularly The du 1 command should be executed after hours regularly e g daily and the output kept in an accessible file for later comparison In this way you can spot users who are rapidly increasing their disk usage The find 1 can be used to locate inactive or large files Example find mtime 90 atime 90 print gt somefile records in somefile the names of files neither written nor accessed in the last 90 days Of course this works best if you are super user e You will also have to balance usage between file systems To do this you will have to move user directories Users should be taught to accept file system name changes and to program around them preferably ahead of time The user s login directory name available in the shell variable HOME should be utilized to minimize path name dependencies User groups with more extensive file syst
8. once a year The most recent weekly tapes should be kept off premises The other tapes should be in a fire proof safe if you can afford one When UNIX goes down active files can get scrambled Your users will not want to start the day over every time your system fails In addition to good backup you must have file system patching expertise available on site or on call If you ever re boot the system for general use without checking out the file systems terrible things will happen we once had five duplicate entries on a file system free list this ruined over 100 new files in just three days Study fsck 1M and crash 8 as well as FSCK The UNIX TS File System Check Program 8 UNIX FILE SYSTEM BACKUP PROGRAMS The following backup programs are distributed e Dump restor This is a familiar tape based system that has been used for several years Full dumps are usually taken when the dump program warns that an incremental dump will run to more than one reel e Find cpio UNIX is distributed in cpio format The cpio option of the find command has made it time competitive with dump restor However it does not produce a perfect restore from a full dump plus incremental dump new and changed files are OK but file removal information is lost Because of this full dumps should be taken fairly often weekly bi weekly Cio is the only program listed here that makes system independent copies It can be used to move files between variou
9. stuck interrupt bit that crashes the system Don t install DZs without giving them the full diagnostic treatment e Synchronous Ports High speed synchronous interface devices are even more trouble than dial equipment The following is a list of potential trouble spots Your UNIX software Your interface device e g DQS11B Cable to your modem Your modem The communications line Administrative Advice for UNIX 9 Other modem Other cable Other interface device Other system s software Think of the finger pointing possibilities The best defense is a good line monitor e Power Supply Modules There are a lot of them and they do fail more or less regularly Hard failure can be detected at the console voltage drift is tougher Failure of the FP11 floating point unit power supply can be slow to fix because Customer Engineers are likely to work back from the far end of the bus taking a long time to find the problem Asynchronous Line Problems Rules 12 3 45 67 89 0 Condition Line rings NYYYYYYYYY Ring light shows on telephone console N YY YY YYYY Computer answers NNYYYYYVY Login message received on terminal NNYYYY Switching modem solves problem Y N Y N User can login NNNY Telephone console shows data received Y YN Problem affects whole DH DZ up t
10. 6 PHOTOTYPESETTING EQUIPMENT AND SUPPLIES Read this section if you plan to use the phototypesetting software of UNIX Phototypesetter The phototypesetter and fonts currently supported by UNIX are manufactured by Wang Graphic Systems Inc Executive Drive Hudson NH 03051 603 889 8550 The phototypesetter is an on line C A T System 1 with a high speed turret The external paper tape reader on the typesetter is not needed because the typesetter is connected to the PDP 11 CPU via a DR11C PDP 11 45 Only The following modification developed by DEC Field Service should be made to the DR11C without this modification the system may crash when the typesetter is powered down Add two 390 ohm resistors from E 18 pin 6 to ground and from E 18 pin 3 to ground Put a piece of insulating tubing over the leads so that they do not short out the etch runs that they cross Fonts There are eight fonts that are normally used as shown in the table below The first three of the these provide the most often used serif typeface The last three are used when a sans serif typeface is desired The fourth font contains a number of Greek characters and mathematical symbols see NROFF TROFF User s Manual by J F Ossanna The fifth font is useful for typesetting text that you wish to look like terminal or printer output e g for examples of programs Wang Graphic Systems Inc offers a variety of other fonts For troff to be able to use thes
11. Administrative Advice for UNIX R Haight The material presented here is based on the author s experiences and opinions Nevertheless it may prove useful The material on phototypesetting was contributed by D W Smith 1 ADMINISTRATOR S ROAD MAP Getting started as a UNIX system administrator is hard work There are no real shortcuts to a working knowledge of the system You will need time for reading study and hands on experimenting Don t commit yourself to going live with your system until you have had two weeks to teach yourself your job and get the initial hardware quirks ironed out Don t consign the Setting Up UNIX document to oblivion after your initial system gen In addition to needing it again whenever you add change equipment you will find that it contains valuable material about system tuning buffers clists etc that appears nowhere else As an administrator you should be familiar with a lot of the distributed documentation The Internals Operations and Administration papers from Documents for UNIX should all be studied as well as the Introduction How to Get Started and most of the entries of the UNIX User s Manual In that manual you should pay special attention to acct 1M chmod 1 chown 1 config 1M cpio 1 date 1 df 1 du 1 ed 1 env 1 find 1 fsck 1M kill 1 mail 1 mkdir 1 mkfs 1M ncheck 1M ps 1 rm 1 rmdir 1 shutdown 1M stty 1 su 1 sync 1M time 1 vol
12. copy 1M wall 1M who 1 and write 1 in Section 1 all of Section 4 acct 5 in Section 5 and crash 8 and varops 8 in Section 8 2 SYSTEM CAPACITY The figures below are approximations based on our experience over several years Number of Hardware Configuration Simultaneous Users PDP 11 23 256K byte memory 2 RLO1 disks 4 PDP 11 34 256K byte memory with cache 2 RLO1 disks 8 PDP 11 45 248K byte memory RP03 disk 16 Above with RP06 RP04 RP05 disk 20 Above with memory cache 25 PDP 11 70 512K byte memory RP06 RP04 RPO5 disks 2 or more drives 32 Above with 768K byte memory and a disk drive or fixed head disk set aside for the root file system 40 VAX 11 780 1M byte memory at least 3 RP06 disks 48 Or equivalent See Setting Up UNIX for the list of supported hardware options t UNIX is a Trademark of Bell Laboratories 2 Administrative Advice for UNIX 3 DISK FREE SPACE Making files is easy under UNIX It has been said that the only standard thing about all UNIX systems is the message of the day telling users to clean up their files Administratively both free disk blocks and free inodes UNIX talk for file headers can be a problem If the free inode count falls below 100 the system spends most of its time rebuilding the free inode array If a file system runs out of space the system prints no space messages and does little else To avoid problems the following start of
13. e fonts corresponding font tables must be built and compiled into the directory usr lib font Administrative Advice for UNIX 11 Name Part Number Troff Name BT Times Roman 802 016A R Times Italic 802 013A I Times Bold 802 014A B BT PI Font 4 Special Characters 829 021B S BT PI Font 6 Constant Width 829 046 A CW Geneva Helvetica Regular 803 032B G or H Geneva Helvetica Regular Italic 803 033B GI or HI Geneva Helvetica Medium 803 034B GM or HM Other fonts for which the source font tables are supplied are Name Troff Name Boston Condensed BC News Condensed C Century Schoolbook Expanded CE Century Schoolbook Italic CI Century Bold Italic CK Century Schoolbook CS Futura Utica Demibold FD or UD Text Greek GR Geneva Light L Geneva Light Italic LI Palatino PA Palatino Bold PB Palatino Italic PI Stymie Bold SB Stymie Medium Italic SI Stymie Medium SM Paper and Chemicals The phototypesetter prints onto photo mechanical paper which can be obtained from a photographic supply house and is specified as e Kodak Ektamatic Paper Grade S Type 2250 8 in x150 ft Spec 175 or equivalent Also obtainable from such a supply house are the chemicals for the developing process e Kodak Ektamatic A10 Activator or equivalent e Kodak Ektamatic S40 Stabilizer or equivalent These chemicals should be ordered in 9 5 liter 2 5 gallon containers for the circulator Developer A Kodak Ektamat
14. em structures should set up a shell variable to refer to the file system name e g FS e The find 1 and cpio 1 commands can be used to move user directories and to manipulate the file system tree The following sequence is useful it moves via magnetic tape the directory trees userx and usery from file system filesys1 to file system filesys2 where presumably more space is available Administrative Advice for UNIX 5 cd filesys1 find userx usery cpio dev rmt0 cd filesys2 mkdir userx usery chown userx userx chown usery usery cpio idmB lt dev rmt0 Make sure new copy is OK Change userx and usery login directories in the etc passwd file rm rf filesysl userx filesys1 usery When moving more than one user in this way Keep users with common interests in the same file system they may have linked files Move groups of users who may have linked files with a single cpio otherwise linked files will be unlinked and duplicated 10 REORGANIZING FILE SYSTEMS The procedure for moving users described above can be expanded to provide a way to reorganize whole file systems Reorganization can improve system response time This is particularly true of the root file system which must be reorganized with all other file systems unmounted and usr Unfortunately reorganization of large file systems is slow 11 KEEPING DIRECTORY FILES SMALL Directories larger than 5K bytes 320 entries are very inefficient
15. ic Processor Model 214K or equivalent is used to process the paper from the typesetter A light proof box attached to the 214K to hold the output cassette from the typesetter is called an Autofeeder and can be obtained from Peripheral Graphics Inc Andover Industrial Center York Street Andover MA 01810 617 475 9005 Circulator and Dryer A circulator and a paper dryer as well as a shelf for the dryer can be obtained from Mohr Enterprises 8015 North Ridgeway Ave Skokie IL 60076 312 674 8890 12 Administrative Advice for UNIX The needed parts are e ME 8 Mohrflow circulator to increase the usability of the chemicals e ME 5 Mohrdry dryer for the photo mechanical paper e Dryer Extension shelf to support the dryer it connects to the circulator cabinet Also obtainable from Mohr Enterprises are cleaners for the developer and circulator Such cleaning is needed every 2 to 4 weeks depending on the volume of work e R 53 Mohrchem Activator Cleaner Concentrate e R 57 Mohrchem Stabilizer Cleaner Concentrate Each quart bottle makes 9 5 liters 2 5 gallons of reusable cleaner to clean the tubing rollers and tray of the developer and circulator Equivalent cleaners can also be obtained elsewhere June 1980
16. o 16 lines YN Diagnosis and or Action No problem X PDP 11 hardware problem likely X X X Telephone problem likely X X X X X May be a problem with user s terminal X Busy out bad line s XXXXXXX X 23 DATASET OPTIONS The following dataset options seem to work with UNIX The 801C L1 Auto Call Unit Jumpers E2 to E3 E6 to E5 Options Y X T B ZG ZP G R ZT Switches 0 open 1 closed i e side next to number is down Si 1000 1 Bracketed switches are missing on some models S2 0101 S3 11010 S4 11 00 The 212A L1 1 200 baud full duplex Options E ZF YF YC YG YJ YK S V A T ZH W YP YR 10 Administrative Advice for UNIX Switches S1 0 001 S2 110001000 S3 11110000 S5 00 24 NULL MODEM WIRING Improperly wired null modems can cause spurious interrupts especially at higher baud rates A single bad modem on a 9 600 baud line can waste 15 of your CPU power The following symmetrical wiring plan will prevent such problems pin 1 to 1 pin 2 to 3 pin 3 to 2 strap pin 4 to 5 in the same plug pin 6 to 20 pin 7 to 7 pin 8 to 20 pin 20 to 6 and 8 ground unused pins 25 113D 103J DATA SET PROBLEMS The DH11 and DJ11 multiplexers normally have a jumper connecting pin 25 to pin 4 request to send thus asserting pin 25 when the line is opened This jumper should be removed for any lines connected to 113Ds or 103Js also applies to 103Js with 801s 2
17. rative Advice for UNIX 3 ERROR DURING WRITE CHECK Error register values are printed below the message The two registers of interest are RPER1 and RPEC2 A RPER1 value of 1000000 indicates ECC no other bits on The RPEC2 register describes the bit span of the error For example RPEC2 003774 means that there was an unacceptable 9 bit binary 0000011111111100 error burst RPEC2 000240 is an acceptable 3 bit span 0000000010100000there may be zero bits mixed in If such acceptable errors account for all unrecoverable errors reported and there aren t too many of them then you have a flag free pack On the VAX even this scant information was not available so we have written our own formatter it tells its tale in English see rp6fmt 8 We plan to make this program available in the future along with other UNIX oriented diagnostics for the PDP 11 as well 7 PROTECTING USER FILES Users especially inexperienced ones occasionally remove their own files Open files are sometimes lost when the system crashes Once in a great while an entire file system will be destroyed picture a disk controller that goes bad and writes when it should read Here is a suggested file backup procedure e Each day copy all user file systems to backup packs Keep these packs 3 to 5 days before re using them e Once a week copy each file system to tape Keep weekly tapes for 8 weeks e Keep bi monthly tapes forever they should be re copied
18. rvice contract learn the details In particular make sure that preventive maintenance is scheduled in advance and that it is completed e Ask the hardware service contractor to provide and maintain a site log You will Administrative Advice for UNIX have to work on the log as well e Make sure that your hardware vendor as well as your hardware service contractor if the two are different agrees to the presence of non DEC equipment on your system even if you have none to start with e Run error logging Keep console sheets Make sure error messages are shown to your contractor s Customer Engineers e Take core dumps after system crashes and interpret results for Customer Engineers e Keep down time records and make sure that your hardware service contractor knows about them Dealing with the telephone services vendor You are most apt to have telephone problems when you rearrange or add equipment You may also have occasional central office trunking and modem failures e Be specific with repair operators tell them that the trouble involves data equipment e If your first call fails to get results ask for the supervisor on the second call and if necessary escalate further to get the problem solved Some obvious problem areas e Disk Drives Over 50 of your problems are likely to be related to the disk subsystem As mentioned earlier the way to keep your system up is to have a spare disk drive Remember
19. s versions of UNIX RT and UNIX and can be used in system conversion e Volcopy physical file system copying to disk or tape For those who can afford a spare drive volcopy to disk provides convenient file restore and quick recovery from disk disasters remember the spare drive Tape volcopy provides good long term backup because the file system can be read in fairly quickly mounted and browsed over Disk and tape volcopy are generally used together for short and long term backup Volcopy can also be used for full dumps with either dump restor or cpio find The table below summarizes attributes of these programs The file system size is 65 500 blocks in all cases times are in minutes judgements are subjective 4 Administrative Advice for UNIX dump restor find cpio volcopy disk volcopy tape Full dump time AO AO 2 15 Incremental dump time 6 7 a Full restore time 40 80 2 15 Incremental restore time 8 10 Ease of restoring one file fair fair good fair a directory poor fair good good scattered files poor poor good good full restore fair fair very good good Needs tape drive yes yes no yes Needs spare file system only when restoring no no yes Needs spare disk drive two CPUs can share yes Maintains pack tape labels no no yes yes Handles multi reel tape yes yes yes 512 blocks per record 1 10 1 10 88 10 Interactive i e ties up console no yes yes yes May require separate ID space no
20. tdown and _ filesave u procedures the file system check program fsck 1M 9 option will help keep the disk free list in reasonable order e Try to keep disk drive usage balanced If you have over 20 users the root file system bin tmp etc and swap deserves a drive of its own e If you have a noisy modem poorly executed do it yourself null modem or a disconnected modem cable UNIX will spend a lot of CPU time trying to get it logged in A random check of systems uncovers a lot of this going on 5 WHY YOU MUST HAVE A SPARE DISK DRIVE e Without a spare disk drive the system will be down when a drive is down e Without a spare drive it is difficult to reorganize file systems or to restore user files 6 DISK PACKS e Buy only fully ECC correctable packs and test them e If a pack develops uncorrectable errors recondition it or get rid of it RP06 disk packs used with UNIX need not be totally error free but must be flag free The term flag free means that there should be no unrecoverable ECC Error Correcting Code errors Technically proper ECC handling can recover from 11 bit error bursts However we hear that the length of bursts can grow as a pack ages We recommend that no pack that has more than 8 bit error bursts be accepted For the PDP 11 the following explanation may help paraphrased from a DEC source In reading the formatter printout ECC correctable errors are identified by the headings DATA Administ
21. utomatic policing will be invariably subverted by users 17 BIRD DOGGING When the system is busy lines busy and or slow response someone should determine why this is so The who 1 command lists the people logged in The ps 1 command shows what they are doing The etc whodo command combines the output of who and ps Unfortunately ps operates from heuristics that can consistently fail to report certain processes in a busy system That is one must be careful about hanging up an apparently inactive line The acctcom 1M command can read the shell accounting file usr adm pacct backwards from the most recent entry It will print entries for selected lines or login names 18 300 1 200 BAUD TERMINALS Don t use upper case only terminals Get full duplex full ASCII terminals Hardware horizontal tabbing is very desirable because it increases output speed and lowers system overhead A fair proportion of your terminals should provide for correspondence quality hard copy output to take advantage of the UNIX word processing capabilities see term 7 19 LINE PRINTERS Most line printers are troublesome and impose considerable overhead on the system Most also lack hardware tabs character overstrike capability etc A printer that will work over an asynchronous link DC1 DC3 protocol required may be the best bet Administrative Advice for UNIX 7 20 SECURITY The current UNIX is not tamper proof You can t keep people from
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