AIX/HP-UX Interoperability Guide (continued)
[Last Chapter: 5. Devices]
AIX supports both the AT&T and the BSD form of the ps command. To use the BSD form, simply leave off the minus sign for the command options, for example:
# ps alx
The AT&T version of the above command is:
# ps -elf
Both of the above commands provide, among other things, the priority and nice values for each process. The nice value is part of the calculation for the priority value, whose range is 0 to 127. The lower the priority value, the more frequently the process is scheduled. Higher numbers mean lower priority.
The nice command follows the BSD value range of -20 to 20, again with the larger number representing the lower priority. Though the AIX man page does not say so, the nice command syntax takes two forms: nice -value and nice -n value. The latter is easier when you have to use negative values. Otherwise, to set the nice value to -10, you have to type:
# nice --10 CommandName
The renice command, unlike in HP-UX, does not take a -n option. The syntax of renice is:
# renice Priority -p PID
Like HP-UX, AIX really has two kill commands: /bin/kill and the kill built-in KornShell command. The signals for each differ. For example:
# /bin/kill -l NULL HUP INT QUIT ILL TRAP IOT EMT FPE KILL BUS SEGV SYS PIPE ALRM TERM URG STOP TSTP CONT CHLD TTIN TTOU IO XCPU XFSZ MSG WINCH PWR USR1 USR2 PROF DANGER VTALRM MIGRATE PRE GRANT RETRACT SOUND SAK # kill -l 1) HUP 14) ALRM 27) MSG 40) bad trap 53) bad trap 2) INT 15) TERM 28) WINCH 41) bad trap 54) bad trap 3) QUIT 16) URG 29) PWR 42) bad trap 55) bad trap 4) ILL 17) STOP 30) USR1 43) bad trap 56) bad trap 5) TRAP 18) TSTP 31) USR2 44) bad trap 57) bad trap 6) LOST 19) CONT 32) PROF 45) bad trap 58) bad trap 7) EMT 20) CHLD 33) DANGER 46) bad trap 59) bad trap 8) FPE 21) TTIN 34) VTALRM 47) bad trap 60) GRANT 9) KILL 22) TTOU 35) MIGRATE 48) bad trap 61) RETRACT 10) BUS 23) IO 36) PRE 49) bad trap 62) SOUND 11) SEGV 24) XCPU 37) bad trap 50) bad trap 63) SAK 12) SYS 25) XFSZ 38) bad trap 51) bad trap 13) PIPE 26) bad trap 39) bad trap 52) bad trap
AIX also has a killall command that any user can run to kill all of his or her processes except the sending process. The syntax is:
# killall -Signal
AIX has a unique way of managing processes: the System Resource Controller (SRC). The SRC takes the form of a daemon, srcmstr, which is started by init via /etc/inittab. srcmstr manages requests to start, stop, or refresh a daemon or a group of daemons. Instead of typing the name of a daemon to start it, or instead of using the kill command to stop a daemon, you use an SRC command that does it for you. In this way you don't have to remember, for example, whether to use an ampersand when starting a daemon, or what signal to use when killing one. SRC also allows you to stop and start groups of related daemons with one command.
AIX has a hierarchical organization of system processes, and this organization is configured into the ODM in the form of the SRCsubsys and SRCsubsvr object classes. Daemons at the lowest levels are subservers. On a newly loaded system the only subservers are those of the inetd subsystem: ftp, telnet, login, finger, etc. To view these subservers, use the odmget command:
# odmget SRCsubvr
SRCsubsvr:
sub_type = "ftp"
subsysname = "inetd"
sub_code = 21
SRCsubsvr:
sub_type = "telnet"
subsysname = "inetd"
sub_code = 23
SRCsubsvr:
sub_type = "finger"
subsysname = "inetd"
sub_code = 79
SRCsubsvr:
sub_type = "tftp"
subsysname = "inetd"
sub_code = 69
...
The next level is that of subsystem. In the above command, we have the inetd subsystem listed in each of the subserver stanzas. To see a list of all subsystems, use the odmget SRCsubsys command:
# odmget SRCsubsys
SRCsubsys:
subsysname = "lpd"
synonym = ""
cmdargs = " "
path = "/usr/lpd/lpd"
uid = 0
auditid = 0
standin = "/dev/console"
standout = "/dev/console"
standerr = "/dev/console"
action = 1
multi = 0
contact = 3
svrkey = 0
svrmtype = 0
priority = 20
signorm = 0
sigforce = 0
display = 1
waittime = 20
grpname = "spooler"
SRCsubsys:
subsysname = "inetd"
synonym = ""
cmdargs = ""
path = "/etc/inetd"
uid = 0
auditid = 0
standin = "/dev/console"
standout = "/dev/console"
standerr = "/dev/console"
action = 2
multi = 0
contact = 3
svrkey = 0
svrmtype = 0
priority = 20
signorm = 0
sigforce = 0
display = 1
waittime = 20
grpname = "tcpip"
...
Related subsystems form a subsystem group, the highest level of the SRC. Subsystem groups can be ascertained from the above command by means of the grpname descriptor. Thus the above output shows the lpd subsystem being part of the spooler subsystem group, and inetd a subsystem of the tcpip subsystem group. An easier way to view all the subsystems and subsystem groups is to use the lssrc -a command:
# lssrc -a Subsystem Group PID Status syslogd ras 3363 active sendmail mail 4646 active portmap portmap 4908 active inetd tcpip 5167 active snmpd tcpip 5428 active keyserv keyserv 6206 active biod nfs 6465 active nfsd nfs 8010 active rpc.mountd nfs 10067 active rpc.statd nfs 10325 active rpc.lockd nfs 10583 active qdaemon spooler 5981 active writesrv spooler 1631 active infod infod 13684 active lpd spooler 12151 active iptrace tcpip inoperative gated tcpip inoperative named tcpip inoperative routed tcpip inoperative rwhod tcpip inoperative timed tcpip inoperative llbd ncs inoperative nrglbd ncs inoperative ypserv yp inoperative ypbind yp inoperative ypupdated yp inoperative yppasswdd yp inoperative
The most commonly used SRC commands are startsrc, stopsrc, and refresh, each of which takes the following options:
| -s | Apply this command to a subsystem, using the subsystem name provided in the lssrclssrc -a command |
| -g | Apply this command to a subsystem group, using the subsystem group name provided in the lssrclssrc -a command |
The names of these commands imply their purpose: to start a subserver, subsystem, or subsystem group, use the startsrc command. For example, to start the rpc.mountd subsystem (which is actually the rpc.mountd daemon) type:
# startsrc -s rpc.mountd
To start the nfs subsystem group:
# startsrc -g nfs
This command starts all the subsystems (daemons) that comprise the nfs subsystem group: nfsd, biod, rpc.mountd, rpc.lockd, and rpc.statd.
To stop a subsystem or subsystem group, use the stopsrc command in exactly the same way. To stop and restart daemons, or to have daemons reread a configuration file such as /etc/inetd.conf, use the refresh command. For example:
# refresh -s inetd
AIX supports an AT&T-style crontab file with each one-line entry containing the following:
AIX also supports a convenient option to the crontab command: the -e option. This option will load the contents of your crontab file into an editing session. The editor used is determined by the value of the EDITOR variable. Once you save and exit from the editing session, your changes become your new crontab file and take effect immediately.
Officially, the crontab spool directories are found in /var/spool/cron, although there is a link from /usr/spool to /var/spool in AIX for compatibility with previous versions of the operating system.
The HP-UX ps command is strictly AT&T-style. Therefore a complete listing of every process is:
# ps -elf
Priorities range from 0 (highest priority) to 256 (lowest priority), and are classified by the following:
HP-UX uses the AT&T version of nice values, which run from 0 to 39 with a default of 20. 39 is the lowest priority, 0 the highest. The HP-UX version of renice has the following syntax:
# renice -n priority_change PID
The new system nice value is equal to 20 + priority_change, and is limited to the range from 0 through 39. If priority_change is a negative value, priority is increased provided the user has appropriate privileges.
HP-UX signals look like the following. For the HP-UX kill command:
# /bin/kill -l
NULL HUP INT QUIT ILL TRAP ABRT EMT FPE KILL BUS SEGV SYS PIPE ALRM TERM USR1 USR2 CHLD PWR VTALRM PROF POLL WINCH STOP TSTP CONT TTIN TTOU URG LOST DIL
For the ksh built-in command:
# kill -l 1) HUP 16) USR1 2) INT 17) USR2 3) QUIT 18) CHLD 4) ILL 19) PWR 5) TRAP 20) VTALRM 6) IOT 21) PROF 7) EMT 22) POLL 8) FPE 23) WINCH 9) KILL 24) STOP 10) BUS 25) TSTP 11) SEGV 26) CONT 12) SYS 27) TTIN 13) PIPE 28) TTOU 14) ALRM 29) URG 15) TERM 30) LOST
The HP-UX killall command is a procedure used by /etc/shutdown to kill all active processes not directly related to the shutdown procedure. It is not used in the same way as in AIX. killall is chiefly used to terminate all processes with open files so that the mounted file systems are no longer busy and can be unmounted.
The top command displays and updates information about the top processes on the system. It summarizes the general state of the system (load average), quantifies the amount of memory in use and free, and reports on individual processes active on the system. Whereas ps gives a single "snapshot" of the system, top samples the system and updates its display at intervals, the default being five seconds. On multiprocessing systems, top reports on the state of each processor.
This command is not available in AIX.
crontab files are found in /usr/spool/cron/crontab and should not be edited directly. Unlike in AIX, there is no -e option to crontab. Therefore to change your cron table you should do the following:
# crontab -l > cron.new
# vi cron.new
# crontab cron.new
# rm cron.new
Of course, you can use any text editor besides vi if you want.
The one-line entries in crontab files are the same for AIX.
AIX supports both the BSD and AT&T versions of the ps command; HP-UX does not. AIX also supports the nice and renice commands, though the nice values differ from those in HP-UX. AIX nice values are from -20 to 20, whereas HP-UX's are from 0 to 39. Both operating systems have two versions of the kill command: /bin/ksh and the ksh built-in, each of which have slightly different signal values. Both systems have similar cron tables, but AIX has a nifty -e option to the crontab command. HP-UX supports the top command, but AIX does not.
The biggest difference to be found with regard to process management between AIX and HP-UX is AIX's System Resource Controller, a daemon that can start, stop, or refresh a daemon or a group of daemons by means of a special set of commands. This mechanism allows for logical startup of several daemons at once as well as for orderly shutdown of daemons. Therefore, in the various "rc" files of AIX, you will see startsrc commands rather than commands to start individual daemons.
Process management between the two systems, with the exception of the System Resource Controller, is similar. To kill a process you can use the most common signals, such as SIGHUP, SIGABRT, SIGKILL, and SIGTERM, which have the same values. Also, since the KornShell is the default shell on both systems, the shell built-in kill and the bgnice option to the ksh set command work the same way.
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