no Command
Purpose
Manages the tuning parameters of the network.
Syntax
no [ -p | -r ] { -o Tunable[=NewValue] }
no -h [Tunable]
Note: Multiple
flags -o, -d, -x, and -L are allowed.
Description
Use the no command to configure parameters that used to tune the network. The no command sets or displays current or next system boot values for network tuning parameters. This command can also make permanent changes or defer changes until the next system reboot. Whether the command sets or displays a parameter, is determined by the accompanying flag. The -o flag does both these actions. It can either display the value of a parameter or set a new value for a parameter. When the no command is used to modify a network option, it logs a message to the syslog by using the LOG_KERN facility.
Understanding
the Effect of Changing Tunable Parameters
Be careful when you use this command. If used incorrectly, the no command can cause your system to become inoperable.
Before you modify any tunable parameter, you must read about all its characteristics in the Tunable Parameters section, and follow the Refer To pointer instructions to understand the purpose. Ensure that the Diagnosis and Tuning sections for this parameter apply to the situation, and changing the value of this parameter helps to improve the performance of your system.
If the Diagnosis and Tuning sections both contain N/A,
you must not change this parameter unless directed by AIX® development.
Flags
| Item | Description |
|---|---|
| -a | Displays current, reboot (when used with -r) or permanent
(when used with -p) value for all tunable parameters, one per
line in pairs Tunable = Value. For the permanent
options, a value displays for a parameter if its reboot and current
values are equal. Otherwise NONE displays as the
value. |
| -d Tunable | Resets Tunable to its default value. If Tunable must
be changed when, it is set to one of the following values:
|
| -D | Resets all tunable parameters to their default value. If a
tunable parameter that must be changed, is of one of the following
types:
|
| -F | Forces restricted tunable parameters to be displayed when the options -a, -L or -x are specified on the command line. If you do not specify the -F flag, restricted tunables are not included, unless they are named in association with a display option. |
| -h [Tunable] | Displays help about Tunable parameter if one is specified. Otherwise, displays the no command usage statement. |
| -L [Tunable] | Lists the characteristics of one
or all Tunables, one per line, by using the following format:
|
| -o Tunable [=NewValue ] | Displays the value or sets the Tunable to NewValue.
If a tunable must be changed, that is the specified value is different
from current value, and is one of the following types:
When -r is
used in combination without a new value, the nextboot value for Tunable is
displayed. When -p is used in combination without a new value,
a value displays only if the current and next boot values for tunable
are the same Otherwise |
| -p | Changes are applied to both current and reboot values when
used in combination with -o, -d or -D, that is
turns on updating of the /etc/tunables/nextboot file
in addition to updating of the current value. These combinations cannot
be used on Reboot and Bosboot type parameters because their current
value cannot be changed. When used with -a or -o without
specifying a new value, the values are displayed when the current
and next boot values for a parameter are the same. Otherwise |
| -r | Changes are applied to reboot values when used in combination with -o, -d, or -D flags, that is it turns on updating the /etc/tunables/nextboot file. If any parameter of type Bosboot is changed, the user is prompted to run bosboot. When used with -a or -o without specifying a new value, next boot values for tunables display instead of the current values. |
| -x [Tunable] | Lists characteristics of one or all tunables,
one per line, by using the following (spreadsheet) format: |
If you change by using the -o, -d or -D flag to a restricted tunable parameter, it results in a warning message that a tunable parameter of the restricted-use type is modified. If you also specify the -r or -p options on the command line, you are prompted for confirmation of the change. During system reboot, the presence of restricted tunables in the /etc/tunables/nextboot file that were modified to a value different from their default value by using a command line and by specifying the -r or -p options, results in an error log entry that identifies the list of these modified tunables.
If you change by using the -o, -d, or -D flag to a parameter of type Mount, it results in a warning message that the change is effective for future mountings.
If you change to a parameter of type Connect by using the -o, -d or -D flag, it results in starting the inetd and displays a warning message that the change is effective for future socket connections.
If you change to a parameter of type Bosboot or Reboot by using the -o, -d, or -D flag and without using the -r flag, it results in an error message.
If you change the current value of a parameter of type Incremental with a new value that is smaller than the current value by using the -o, -d, or -D flag and without using the -r flag, it results in an error message.
Tunable
Parameters Type
All the tunable parameters that are
manipulated by the tuning commands such as no, nfso, vmo, ioo, schedo,
and raso commands are classified into the following
categories:
For parameters of type Bosboot, whenever there is a change,
the tuning commands automatically prompt the user to ask if they want
to run the bosboot command. For parameters of type
Connect, the tuning commands automatically restart the inetd daemon
if pre520tune is disabled.
| Item | Description |
|---|---|
| Dynamic | If the parameter can be changed at any time |
| Static | If the parameter can never be changed |
| Reboot | If the parameter can be changed during reboot |
| Bosboot | If the parameter can be changed by running bosboot and rebooting the machine |
| Mount | If changes to the parameter are only effective for future file systems or directory mounts |
| Incremental | If the parameter can be incremented, except at boot time |
| Connect | If changes to the parameter are only effective for future socket connections |
| Deprecated | If this parameter cannot be changed and is no longer supported by the current release of AIX. |
Note: The current set of parameters
that are managed by the no command includes Reboot,
Static, Dynamic, Incremental, and Connect types.
Tunable
Parameters
For default values and range of values
for tunables, refer the no command help (-h <tunable_parameter_name>).
| Item | Description |
|---|---|
| arpqsize |
|
| arpt_killc |
|
| arptab_bsiz |
|
| arptab_nb |
|
| bcastping |
|
| clean_partial_conns |
|
| delayack |
|
| delayackports |
|
| dgd_flush_cached_route |
|
| dgd_packets_lost |
|
| dgd_ping_time |
|
| dgd_retry_time |
|
| directed_broadcast |
|
| fasttimo |
|
| hstcp |
|
| icmp6_errmsg_rate |
|
| icmpaddressmask |
|
| icmptimestamp |
|
| ie5_old_multicast_mapping |
|
| ifstat32 |
|
| ifsize |
|
| ip6_defttl |
|
| ip6_prune |
|
| ip6forwarding |
|
| ip6srcrouteforward |
|
| ip_ifdelete_notify |
|
| ip_ifdelete_no_retrans |
|
| ip_nfrag |
|
| ipforwarding |
|
| ipfragttl |
|
| ipignoreredirects |
|
| ipqmaxlen |
|
| ipoutqueues |
|
| ipsendredirects |
|
| ipsrcrouteforward |
|
| ipsrcrouterecv |
|
| ipsrcroutesend |
|
| limited_ss |
|
| llsleep_timeout |
|
| lo_perf |
|
| lowthresh |
|
| main_if6 |
|
| main_site6 |
|
| maxnip6q |
|
| maxttl |
|
| medthresh |
|
| mpr_policy |
|
| multi_homed |
|
| nbc_limit |
|
| nbc_max_cache |
|
| nbc_min_cache |
|
| nbc_ofile_hashsz |
|
| nbc_pseg |
|
| nbc_pseg_limit |
|
| ndd_event_name |
|
| ndd_event_tracing |
|
| ndp_mmaxtries |
|
| ndp_umaxtries |
|
| ndpqsize |
|
| ndpt_down |
|
| ndpt_keep |
|
| ndpt_probe |
|
| ndpt_reachable |
|
| ndpt_retrans |
|
| net_buf_size |
|
| net_buf_type |
|
| net_malloc_frag_mask |
|
| netm_page_promote |
|
| nonlocsrcroute |
|
| nstrpush |
|
| passive_dgd |
|
| pmtu_default_age |
|
| pmtu_expire |
|
| pmtu_rediscover_interval |
|
| psebufcalls |
|
| psecache |
|
| psetimers |
|
| rfc1122addrchk |
|
| rfc1323 |
|
| rfc2414 |
|
| route_expire |
|
| routerevalidate |
|
| rto_high |
|
| rto_length |
|
| rto_limit |
|
| rto_low |
|
| sack |
|
| sb_max |
|
| send_file_duration |
|
| site6_index |
|
| sockthresh |
|
| sodebug |
|
| sodebug_env |
|
| somaxconn |
|
| soreuseport_lb |
|
| strctlsz |
|
| strmsgsz |
|
| strthresh |
|
| strturncnt |
|
| subnetsarelocal |
|
| tcp_bad_port_limit |
|
| tcp_cwnd_modified |
|
| tcp_ecn |
|
| tcp_ephemeral_high |
|
| tcp_ephemeral_low |
|
| tcp_fastlo |
|
| tcp_finwait2 |
|
| tcp_icmpsecure |
|
| tcp_init_window |
|
| tcp_inpcb_hashtab_siz |
|
| tcp_keepcnt |
|
| tcp_keepidle |
|
| tcp_keepinit |
|
| tcp_keepintvl |
|
| tcp_limited_transmit |
|
| tcp_low_rto |
|
| tcp_maxburst |
|
| tcp_maxqueuelen |
|
| tcp_mssdflt |
|
| tcp_nagle_limit |
|
| tcp_nagleoverride |
|
| tcp_ndebug |
|
| tcp_newreno |
|
| tcp_nodelayack |
|
| tcp_pmtu_discover |
|
| tcp_recvspace |
|
| tcp_sendspace |
|
| tcp_syn_rto |
|
| tcp_tcpsecure |
|
| tcp_timewait |
|
| tcp_ttl |
|
| tcprexmtthresh |
|
| tcptr_enable |
|
| thewall |
|
| timer_wheel_tick |
|
| tn_filter |
|
| udp_bad_port_limit |
|
| udp_ephemeral_high |
|
| udp_ephemeral_low |
|
| udp_inpcb_hashtab_siz |
|
| udp_pmtu_discover |
|
| udp_recvspace |
|
| udp_send_perf |
|
| udp_sendspace |
|
| udp_ttl |
|
| udpcksum |
|
| use_sndbufpool |
|
Compatibility Mode
When running in pre 5.2 compatibility mode that is controlled by the pre520tune attribute of sys0, see AIX 5.2 compatibility mode. The reboot values for parameters, except those of type Bosboot, are not applicable because in the pre 5.2 compatibility mode they are not applied during boot.
In pre 5.2 compatibility mode, setting reboot values to tuning parameters continues to be achieved by embedding calls to tuning commands in scripts that are called during the boot sequence. Parameters of type Reboot can therefore be set without the -r flag, so that existing scripts continue to work.
This mode is automatically turned ON when a machine is MIGRATED to AIX 5L Version 5.2. For complete installations, it is turned OFF and the reboot values for parameters are set by applying the content of the /etc/tunables/nextboot file during the reboot sequence. Only in that mode are the -r and -p flags fully functional. See Kernel Tuning in the Performance Tools Guide and Reference for details.
Security
Attention RBAC users and Trusted AIX users: This command can perform privileged operations. Only privileged users can run privileged
operations. For more information about authorizations and privileges, see Privileged Command
Database in Security. For a list of privileges and the
authorizations that are associated with this command, see the lssecattr command
or the getcmdattr subcommand.
Examples
- To display the maximum size of the mbuf pool, type:
no -o thewall - To reset the time to live for UDP packets its default size, type:
no -d udp_ttl - To change the default socket buffer sizes on your system, type:
no -r -o tcp_sendspace=32768 no -r -o udp_recvspace=32768 - To use a system as an internet work router over Internet Protocol
networks, type:
no -o ipforwarding=1 - To list the current and reboot value, range, unit, type and dependencies
of all tunable parameters that are managed by the no command,
type:
no -L - To display the help information about the
udp_ephemeral_highoption, type:no -h udp_ephemeral_high - To permanently turn off the
ip6srcrouteforwardoption, type:no -p -o ip6srcrouteforward=0 - To list the reboot values for all Network tuning parameters, type:
no -r -a - To list (spreadsheet format) the current and reboot value, range,
unit, type and dependencies of all tunable parameters that are managed
by the no command, type:
no -x - To log all allocations and frees of type
mbuforsocketthat are size256or4096, type:no -o net_buf_type={mbuf:socket} -o net_buf_size={256:4096} -o net_malloc_police=1 - To log all allocations and frees of type
mbuf, type:no -o net_buf_type={mbuf} -o net_buf_size={all} -o net_malloc_police=1 - To log all ns_allocs and ns_frees for
en0oren3by using a 2000 events buffer size, type:no -o ndd_event_name={en0:en3} -o ndd_event_tracing=2000 - To log all ns_allocs and ns_frees for all
enadapters by using a 2000 events buffer size, type:no -o ndd_event_name={en} -o ndd_event_tracing=2000 - To log all ns_allocs and ns_frees for all adapters,
type:
no -o ndd_event_name={all} -o ndd_event_tracing=1