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@(#)6.t 8.1 (Berkeley) 7/27/93
.Sh 1 "System operation"
This section describes procedures used to operate a \*(4B UNIX system. Procedures described here are used periodically, to reboot the system, analyze error messages from devices, do disk backups, monitor system performance, recompile system software and control local changes. .Sh 2 "Bootstrap and shutdown procedures"
In a normal reboot, the system checks the disks and comes up multi-user without intervention at the console. Such a reboot can be stopped (after it prints the date) with a ^C (interrupt). This will leave the system in single-user mode, with only the console terminal active. (If the console has been marked ``insecure'' in
n /etc/ttys you must enter the root password to bring the machine to single-user mode.) It is also possible to allow the filesystem checks to complete and then to return to single-user mode by signaling .Xr fsck (8) with a QUIT signal (^\|\e).
To bring the system up to a multi-user configuration from the single-user status, all you have to do is hit ^D on the console. The system will then execute
n /etc/rc , a multi-user restart script (and
n /etc/rc.local ), and come up on the terminals listed as active in the file
n /etc/ttys . See .Xr init (8) and .Xr ttys (5) for more details. Note, however, that this does not cause a filesystem check to be done. Unless the system was taken down cleanly, you should run ``fsck -p'' or force a reboot with .Xr reboot (8) to have the disks checked.
To take the system down to a single user state you can use # kill 1 or use the .Xr shutdown (8) command (which is much more polite, if there are other users logged in) when you are running multi-user. Either command will kill all processes and give you a shell on the console, as if you had just booted. Filesystems remain mounted after the system is taken single-user. If you wish to come up multi-user again, you should do this by: # cd / # /sbin/umount -a # ^D
Each system shutdown, crash, processor halt and reboot is recorded in the system log with its cause. .Sh 2 "Device errors and diagnostics"
When serious errors occur on peripherals or in the system, the system prints a warning diagnostic on the console. These messages are collected by the system error logging process .Xr syslogd (8) and written into a system error log file
n /var/log/messages . Less serious errors are sent directly to .Xr syslogd , which may log them on the console. The error priorities that are logged and the locations to which they are logged are controlled by
n /etc/syslog.conf . See .Xr syslogd (8) for further details.
Error messages printed by the devices in the system are described with the drivers for the devices in section 4 of the programmer's manual. If errors occur suggesting hardware problems, you should contact your hardware support group or field service. It is a good idea to examine the error log file regularly (e.g. with the command tail -r /var/log/messages). .Sh 2 "Filesystem checks, backups, and disaster recovery"
Periodically (say every week or so in the absence of any problems) and always (usually automatically) after a crash, all the filesystems should be checked for consistency by .Xr fsck (1). The procedures of .Xr reboot (8) should be used to get the system to a state where a filesystem check can be done manually or automatically.
Dumping of the filesystems should be done regularly, since once the system is going it is easy to become complacent. Complete and incremental dumps are easily done with .Xr dump (8). You should arrange to do a towers-of-hanoi dump sequence; we tune ours so that almost all files are dumped on two tapes and kept for at least a week in most every case. We take full dumps every month (and keep these indefinitely). Operators can execute ``dump w'' at login that will tell them what needs to be dumped (based on the
n /etc/fstab information). Be sure to create a group operator in the file
n /etc/group so that dump can notify logged-in operators when it needs help.
More precisely, we have three sets of dump tapes: 10 daily tapes, 5 weekly sets of 2 tapes, and fresh sets of three tapes monthly. We do daily dumps circularly on the daily tapes with sequence `3 2 5 4 7 6 9 8 9 9 9 ...'. Each weekly is a level 1 and the daily dump sequence level restarts after each weekly dump. Full dumps are level 0 and the daily sequence restarts after each full dump also.
Thus a typical dump sequence would be:
| tape name level number date opr size |
| FULL 0 Nov 24, 1992 operator 137K |
| D1 3 Nov 28, 1992 operator 29K |
| D2 2 Nov 29, 1992 operator 34K |
| D3 5 Nov 30, 1992 operator 19K |
| D4 4 Dec 1, 1992 operator 22K |
| W1 1 Dec 2, 1992 operator 40K |
| D5 3 Dec 4, 1992 operator 15K |
| D6 2 Dec 5, 1992 operator 25K |
| D7 5 Dec 6, 1992 operator 15K |
| D8 4 Dec 7, 1992 operator 19K |
| W2 1 Dec 9, 1992 operator 118K |
| D9 3 Dec 11, 1992 operator 15K |
| D10 2 Dec 12, 1992 operator 26K |
| D1 5 Dec 15, 1992 operator 14K |
| W3 1 Dec 17, 1992 operator 71K |
| D2 3 Dec 18, 1992 operator 13K |
| FULL 0 Dec 22, 1992 operator 135K |
Dumping of files by name is best done by .Xr tar (1) but the amount of data that can be moved in this way is limited to a single tape. Finally if there are enough drives entire disks can be copied with .Xr dd (1) using the raw special files and an appropriate blocking factor; the number of sectors per track is usually a good value to use, consult
It is desirable that full dumps of the root filesystem be made regularly. This is especially true when only one disk is available. Then, if the root filesystem is damaged by a hardware or software failure, you can rebuild a workable disk doing a restore in the same way that the initial root filesystem was created.
Exhaustion of user-file space is certain to occur now and then; disk quotas may be imposed, or if you prefer a less fascist approach, try using the programs .Xr du (1), .Xr df (1), and .Xr quot (8), combined with threatening messages of the day, and personal letters. .Sh 2 "Moving filesystem data"
If you have the resources, the best way to move a filesystem is to dump it to a spare disk partition, or magtape, using .Xr dump (8), use .Xr newfs (8) to create the new filesystem, and restore the filesystem using .Xr restore (8). Filesystems may also be moved by piping the output of .Xr dump to .Xr restore . The .Xr restore program uses an ``in-place'' algorithm that allows filesystem dumps to be restored without concern for the original size of the filesystem. Further, portions of a filesystem may be selectively restored using a method similar to the tape archive program.
If you have to merge a filesystem into another, existing one, the best bet is to use .Xr tar (1). If you must shrink a filesystem, the best bet is to dump the original and restore it onto the new filesystem. If you are playing with the root filesystem and only have one drive, the procedure is more complicated. If the only drive is a Winchester disk, this procedure may not be used without overwriting the existing root or another partition. What you do is the following:
Note that if you change the disk partition tables or add new disk drivers they should also be added to the standalone system in
n /sys/<architecture>/stand , and the default disk partition tables in
n /etc/disktab should be modified. .Sh 2 "Monitoring system performance"
The .Xr systat program provided with the system is designed to be an aid to monitoring systemwide activity. The default ``pigs'' mode shows a dynamic ``ps''. By running in the ``vmstat'' mode when the system is active you can judge the system activity in several dimensions: job distribution, virtual memory load, paging and swapping activity, device interrupts, and disk and cpu utilization. Ideally, there should be few blocked (b) jobs, there should be little paging or swapping activity, there should be available bandwidth on the disk devices (most single arms peak out at 20-30 tps in practice), and the user cpu utilization (us) should be high (above 50%).
If the system is busy, then the count of active jobs may be large, and several of these jobs may often be blocked (b). If the virtual memory is active, then the paging demon will be running (sr will be non-zero). It is healthy for the paging demon to free pages when the virtual memory gets active; it is triggered by the amount of free memory dropping below a threshold and increases its pace as free memory goes to zero.
If you run in the ``vmstat'' mode when the system is busy, you can find imbalances by noting abnormal job distributions. If many processes are blocked (b), then the disk subsystem is overloaded or imbalanced. If you have several non-dma devices or open teletype lines that are ``ringing'', or user programs that are doing high-speed non-buffered input/output, then the system time may go high (60-70% or higher). It is often possible to pin down the cause of high system time by looking to see if there is excessive context switching (cs), interrupt activity (in) and per-device interrupt counts, or system call activity (sy). Cumulatively on one of our large machines we average about 60-200 context switches and interrupts per second and about 50-500 system calls per second.
If the system is heavily loaded, or if you have little memory for your load (2M is little in most any case), then the system may be forced to swap. This is likely to be accompanied by a noticeable reduction in system performance and pregnant pauses when interactive jobs such as editors swap out. If you expect to be in a memory-poor environment for an extended period you might consider administratively limiting system load. .Sh 2 "Recompiling and reinstalling system software"
It is easy to regenerate either the entire system or a single utility, and it is a good idea to try rebuilding pieces of the system to build confidence in the procedures.
In general, there are six well-known targets supported by all the makefiles on the system:
n /usr/obj and create a symbolic link in the current source directory to referenced it, named ``obj''. Once this shadow structure has been created, all the files created by .Xr make will live in the shadow structure, and
n /usr/src may be mounted read-only by multiple machines. Doing a make obj in
n /usr/src will build the shadow directory structure for everything on the system except for the contributed, old, and kernel software.
The system consists of three major parts: the kernel itself, found in
n /usr/src/sys , the libraries , found in
n /usr/src/lib , and the user programs (the rest of
Deprecated software, found in
n /usr/src/old , often has old style makefiles; some of it does not compile under \*(4B at all.
Contributed software, found in
n /usr/src/contrib , usually does not support the ``cleandir'', ``depend'', or ``obj'' targets.
The kernel does not support the ``obj'' shadow structure. All kernels are compiled in subdirectories of
n /usr/src/sys/compile which is usually abbreviated as
n /sys/compile . If you want to mount your source tree read-only,
n /usr/src/sys/compile will have to be on a separate filesystem from
n /usr/src can be done by making
n /usr/src/sys/compile a symbolic link that references
n /usr/obj/sys/compile . If it is a symbolic link, the S variable in the kernel Makefile must be changed from
n ../.. to the absolute pathname needed to locate the kernel sources, usually
n /usr/src/sys . The symbolic link created by .Xr config (8) for
n machine must also be manually changed to an absolute pathname. Finally, the
n /usr/src/sys/libkern/obj directory must be located in
Each of the standard utilities and libraries may be built and installed by changing directories into the correct location and doing: # make # make install Note, if system include files have changed between compiles, .Xr make will not do the correct dependency checks if the dependency files have not been built using the ``depend'' target.
The entire library and utility suite for the system may be recompiled from scratch by changing directory to
n /usr/src and doing: # make build This target installs the system include files, cleans the source tree, builds and installs the libraries, and builds and installs the system utilities.
To recompile a specific program, first determine where the binary resides with the .Xr whereis (1) command, then change to the corresponding source directory and build it with the Makefile in the directory. For instance, to recompile ``passwd'', all one has to do is: # whereis passwd /usr/bin/passwd # cd /usr/src/usr.bin/passwd # make # make install this will compile and install the .Xr passwd utility.
If you wish to recompile and install all programs into a particular target area you can override the default path prefix by doing: # make # make DESTDIR=pathname install Similarly, the mode, owner, group, and other characteristics of the installed object can be modified by changing other default make variables. See .Xr make (1),
n /usr/src/share/mk/bsd.README , and the ``.mk'' scripts in the
n /usr/share/mk directory for more information.
If you modify the C library or system include files, to change a system call for example, and want to rebuild and install everything, you have to be a little careful. You must ensure that the include files are installed before anything is compiled, and that the libraries are installed before the remainder of the source, otherwise the loaded images will not contain the new routine from the library. If include files have been modified, the following commands should be done first: # cd /usr/src/include # make install Then, if, for example, C library files have been modified, the following commands should be executed: # cd /usr/src/lib/libc # make depend # make # make install # cd /usr/src # make depend # make # make install Alternatively, the make build command described above will accomplish the same tasks. This takes several hours on a reasonably configured machine. .Sh 2 "Making local modifications"
The source for locally written commands is normally stored in
n /usr/src/local , and their binaries are kept in
n /usr/local/bin . This isolation of local binaries allows
n /bin to correspond to the distribution tape (and to the manuals that people can buy). People using local commands should be made aware that they are not in the base manual. Manual pages for local commands should be installed in
n /usr/local/man/cat[1-8]. The .Xr man (1) command automatically finds manual pages placed in /usr/local/man/cat[1-8] to encourage this practice (see .Xr man.conf (5)). .Sh 2 "Accounting"
UNIX optionally records two kinds of accounting information: connect time accounting and process resource accounting. The connect time accounting information is stored in the file
n /var/log/wtmp , which is summarized by the program .Xr ac (8). The process time accounting information is stored in the file
n /var/account/acct after it is enabled by .Xr accton (8), and is analyzed and summarized by the program .Xr sa (8).
If you need to recharge for computing time, you can develop procedures based on the information provided by these commands. A convenient way to do this is to give commands to the clock daemon
n /usr/sbin/cron to be executed every day at a specified time. This is done by adding lines to
n /etc/crontab.local ; see .Xr cron (8) for details. .Sh 2 "Resource control"
Resource control in the current version of UNIX is more elaborate than in most UNIX systems. The disk quota facilities developed at the University of Melbourne have been incorporated in the system and allow control over the number of files and amount of disk space each user and/or group may use on each filesystem. In addition, the resources consumed by any single process can be limited by the mechanisms of .Xr setrlimit (2). As distributed, the latter mechanism is voluntary, though sites may choose to modify the login mechanism to impose limits not covered with disk quotas.
To use the disk quota facilities, the system must be configured with ``options QUOTA''. Filesystems may then be placed under the quota mechanism by creating a null file
n quota.group at the root of the filesystem, running .Xr quotacheck (8), and modifying
n /etc/fstab to show that the filesystem is to run with disk quotas (options userquota and/or groupquota). The .Xr quotaon (8) program may then be run to enable quotas.
Individual quotas are applied by using the quota editor .Xr edquota (8). Users may view their quotas (but not those of other users) with the .Xr quota (1) program. The .Xr repquota (8) program may be used to summarize the quotas and current space usage on a particular filesystem or filesystems.
Quotas are enforced with soft and hard limits. When a user and/or group first reaches a soft limit on a resource, a message is generated on their terminal. If the user and/or group fails to lower the resource usage below the soft limit for longer than the time limit established for that filesystem (default seven days) the system then treats the soft limit as a hard limit and disallows any allocations until enough space is reclaimed to bring the user and/or group back below the soft limit. Hard limits are enforced strictly resulting in errors when a user and/or group tries to create or write a file. Each time a hard limit is exceeded the system will generate a message on the user's terminal.
Consult the auxiliary document, ``Disc Quotas in a UNIX Environment'' (SMM:4) and the appropriate manual entries for more information. .Sh 2 "Network troubleshooting"
If you have anything more than a trivial network configuration, from time to time you are bound to run into problems. Before blaming the software, first check your network connections. On networks such as the Ethernet a loose cable tap or misplaced power cable can result in severely deteriorated service. The .Xr netstat (1) program may be of aid in tracking down hardware malfunctions. In particular, look at the -i and -s options in the manual page.
Should you believe a communication protocol problem exists, consult the protocol specifications and attempt to isolate the problem in a packet trace. The SO_DEBUG option may be supplied before establishing a connection on a socket, in which case the system will trace all traffic and internal actions (such as timers expiring) in a circular trace buffer. This buffer may then be printed out with the .Xr trpt (8) program. Most of the servers distributed with the system accept a -d option forcing all sockets to be created with debugging turned on. Consult the appropriate manual pages for more information. .Sh 2 "Files that need periodic attention"
We conclude the discussion of system operations by listing the files that require periodic attention or are system specific:
| /etc/fstab how disk partitions are used |
| /etc/disktab default disk partition sizes/labels |
| /etc/printcap printer database |
| /etc/gettytab terminal type definitions |
| /etc/remote names and phone numbers of remote machines for tip(1) |
| /etc/group group memberships |
| /etc/motd message of the day |
| /etc/master.passwd password file; each account has a line |
| /etc/rc.local local system restart script; runs reboot; starts daemons |
| /etc/inetd.conf local internet servers |
| /etc/hosts local host name database |
| /etc/networks network name database |
| /etc/services network services database |
| /etc/hosts.equiv hosts under same administrative control |
| /etc/syslog.conf error log configuration for syslogd\|(8) |
| /etc/ttys enables/disables ports |
| /etc/crontab commands that are run periodically |
| /etc/crontab.local local commands that are run periodically |
| /etc/aliases mail forwarding and distribution groups |
| /var/account/acct raw process account data |
| /var/log/messages system error log |
| /var/log/wtmp login session accounting |
X