linux sysctl命令学习
sysctl命令用于运行时配置内核参数，这些参数位于/proc/sys目录下。
使用sysctl -a可以用来查看当前系统中所有的内核参数配置，
了解这些内核参数的意义对于解决问题会很有帮助。
sh-# sysctl -a
kernel.sched_child_runs_first = 0
kernel.sched_min_granularity_ns = 750000
kernel.sched_latency_ns = 6000000
kernel.sched_wakeup_granularity_ns = 1000000
kernel.sched_tunable_scaling = 1
kernel.sched_migration_cost = 500000
kernel.sched_nr_migrate = 32
kernel.sched_time_avg = 1000
kernel.sched_shares_window = 10000000
kernel.timer_migration = 1
kernel.sched_rt_period_us = 1000000
kernel.sched_rt_runtime_us = 950000
kernel.panic = 0
kernel.core_uses_pid = 0
kernel.core_pattern = core
kernel.core_pipe_limit = 0
kernel.tainted = 1
kernel.print-fatal-signals = 0
kernel.ctrl-alt-del = 0
kernel.modprobe = /sbin/modprobe
kernel.modules_disabled = 0
kernel.hotplug = /sbin/hotplug
kernel.sg-big-buff = 32768
kernel.cad_pid = 1
kernel.threads-max = 4606
kernel.random.poolsize = 4096
kernel.random.entropy_avail = 152
kernel.random.read_wakeup_threshold = 64
kernel.random.write_wakeup_threshold = 128
kernel.random.boot_id = 9e7b0657-6f91-4e94-9c05-55c49dd99da9
kernel.random.uuid = 309f03a1-28d0-47e0-9616-a390bb0349ba
kernel.usermodehelper.bset = 4294967295 4294967295
kernel.usermodehelper.inheritable = 4294967295 4294967295
kernel.overflowuid = 65534
kernel.overflowgid = 65534
kernel.pid_max = 32768
kernel.panic_on_oops = 0
kernel.printk = 7 4 1 7
kernel.printk_ratelimit = 5
kernel.printk_ratelimit_burst = 10
kernel.printk_delay = 0
kernel.dmesg_restrict = 0
kernel.kptr_restrict = 0
kernel.ngroups_max = 65536
kernel.randomize_va_space = 1
kernel.max_lock_depth = 1024
kernel.poweroff_cmd = /sbin/poweroff
kernel.blk_iopoll = 1
kernel.ostype = Linux
kernel.osrelease = 3.0.13
kernel.version = #1 PREEMPT Tue Oct 8 16:24:52 CST 2013
kernel.hostname = 1234
kernel.domainname = (none)
kernel.shmmax = 33554432
kernel.shmall = 2097152
kernel.shmmni = 4096
kernel.msgmax = 8192
kernel.msgmni = 575
kernel.msgmnb = 16384
kernel.sem = 250 32000 32 128
kernel.auto_msgmni = 1
kernel.pty.max = 4096
kernel.pty.nr = 0
vm.overcommit_memory = 0
vm.panic_on_oom = 0
vm.oom_kill_allocating_task = 0
vm.oom_dump_tasks = 1
vm.overcommit_ratio = 50
vm.page-cluster = 3
vm.dirty_background_ratio = 10
vm.dirty_background_bytes = 0
vm.dirty_ratio = 20
vm.dirty_bytes = 0
vm.dirty_writeback_centisecs = 500
vm.dirty_expire_centisecs = 3000
vm.nr_pdflush_threads = 0
vm.swappiness = 60
vm.lowmem_reserve_ratio = 256 32 32
vm.drop_caches = 0
vm.min_free_kbytes = 2188
vm.min_free_order_shift = 1
vm.percpu_pagelist_fraction = 0
vm.max_map_count = 65530
vm.laptop_mode = 0
vm.block_dump = 0
vm.vfs_cache_pressure = 100
vm.mmap_min_addr = 4096
vm.highmem_is_dirtyable = 0
vm.scan_unevictable_pages = 0
fs.inode-nr = 2145 0
fs.inode-state = 2145 0 0 0 0 0 0
fs.file-nr = 297 0 29469
fs.file-max = 29469
fs.nr_open = 1048576
fs.dentry-state = 2777 2184 45 0 0 0
fs.overflowuid = 65534
fs.overflowgid = 65534
fs.leases-enable = 1
fs.dir-notify-enable = 1
fs.lease-break-time = 45
fs.aio-nr = 0
fs.aio-max-nr = 65536
fs.inotify.max_user_instances = 128
fs.inotify.max_user_watches = 8192
fs.inotify.max_queued_events = 16384
fs.epoll.max_user_watches = 111805
fs.suid_dumpable = 0
fs.pipe-max-size = 1048576
fs.mqueue.queues_max = 256
fs.mqueue.msg_max = 10
fs.mqueue.msgsize_max = 8192
dev.scsi.logging_level = 0
net.core.somaxconn = 128
net.core.xfrm_aevent_etime = 10
net.core.xfrm_aevent_rseqth = 2
net.core.xfrm_larval_drop = 1
net.core.xfrm_acq_expires = 30
net.core.wmem_max = 108544
net.core.rmem_max = 108544
net.core.wmem_default = 108544
net.core.rmem_default = 108544
net.core.dev_weight = 64
net.core.netdev_max_backlog = 1000
net.core.netdev_tstamp_prequeue = 1
net.core.message_cost = 5
net.core.message_burst = 10
net.core.optmem_max = 10240
net.core.netdev_budget = 300
net.core.warnings = 1
net.ipv4.route.gc_thresh = 4096
net.ipv4.route.max_size = 65536
net.ipv4.route.gc_min_interval = 0
net.ipv4.route.gc_min_interval_ms = 500
net.ipv4.route.gc_timeout = 300
net.ipv4.route.gc_interval = 60
net.ipv4.route.redirect_load = 4
net.ipv4.route.redirect_number = 9
net.ipv4.route.redirect_silence = 4096
net.ipv4.route.error_cost = 200
net.ipv4.route.error_burst = 1000
net.ipv4.route.gc_elasticity = 8
net.ipv4.route.mtu_expires = 600
net.ipv4.route.min_pmtu = 552
net.ipv4.route.min_adv_mss = 256
net.ipv4.neigh.default.mcast_solicit = 3
net.ipv4.neigh.default.ucast_solicit = 3
net.ipv4.neigh.default.app_solicit = 0
net.ipv4.neigh.default.retrans_time = 100
net.ipv4.neigh.default.base_reachable_time = 30
net.ipv4.neigh.default.delay_first_probe_time = 5
net.ipv4.neigh.default.gc_stale_time = 60
net.ipv4.neigh.default.unres_qlen = 3
net.ipv4.neigh.default.proxy_qlen = 64
net.ipv4.neigh.default.anycast_delay = 100
net.ipv4.neigh.default.proxy_delay = 80
net.ipv4.neigh.default.locktime = 100
net.ipv4.neigh.default.retrans_time_ms = 1000
net.ipv4.neigh.default.base_reachable_time_ms = 30000
net.ipv4.neigh.default.gc_interval = 30
net.ipv4.neigh.default.gc_thresh1 = 128
net.ipv4.neigh.default.gc_thresh2 = 512
net.ipv4.neigh.default.gc_thresh3 = 1024
net.ipv4.neigh.lo.mcast_solicit = 3
net.ipv4.neigh.lo.ucast_solicit = 3
net.ipv4.neigh.lo.app_solicit = 0
net.ipv4.neigh.lo.retrans_time = 100
net.ipv4.neigh.lo.base_reachable_time = 30
net.ipv4.neigh.lo.delay_first_probe_time = 5
net.ipv4.neigh.lo.gc_stale_time = 60
net.ipv4.neigh.lo.unres_qlen = 3
net.ipv4.neigh.lo.proxy_qlen = 64
net.ipv4.neigh.lo.anycast_delay = 100
net.ipv4.neigh.lo.proxy_delay = 80
net.ipv4.neigh.lo.locktime = 100
net.ipv4.neigh.lo.retrans_time_ms = 1000
net.ipv4.neigh.lo.base_reachable_time_ms = 30000
net.ipv4.neigh.eth0.mcast_solicit = 3
net.ipv4.neigh.eth0.ucast_solicit = 3
net.ipv4.neigh.eth0.app_solicit = 0
net.ipv4.neigh.eth0.retrans_time = 100
net.ipv4.neigh.eth0.base_reachable_time = 30
net.ipv4.neigh.eth0.delay_first_probe_time = 5
net.ipv4.neigh.eth0.gc_stale_time = 60
net.ipv4.neigh.eth0.unres_qlen = 3
net.ipv4.neigh.eth0.proxy_qlen = 64
net.ipv4.neigh.eth0.anycast_delay = 100
net.ipv4.neigh.eth0.proxy_delay = 80
net.ipv4.neigh.eth0.locktime = 100
net.ipv4.neigh.eth0.retrans_time_ms = 1000
net.ipv4.neigh.eth0.base_reachable_time_ms = 30000
net.ipv4.neigh.sit0.mcast_solicit = 3
net.ipv4.neigh.sit0.ucast_solicit = 3
net.ipv4.neigh.sit0.app_solicit = 0
net.ipv4.neigh.sit0.retrans_time = 100
net.ipv4.neigh.sit0.base_reachable_time = 30
net.ipv4.neigh.sit0.delay_first_probe_time = 5
net.ipv4.neigh.sit0.gc_stale_time = 60
net.ipv4.neigh.sit0.unres_qlen = 3
net.ipv4.neigh.sit0.proxy_qlen = 64
net.ipv4.neigh.sit0.anycast_delay = 100
net.ipv4.neigh.sit0.proxy_delay = 80
net.ipv4.neigh.sit0.locktime = 100
net.ipv4.neigh.sit0.retrans_time_ms = 1000
net.ipv4.neigh.sit0.base_reachable_time_ms = 30000
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_window_scaling = 6
net.ipv4.tcp_sack = 1
net.ipv4.tcp_retrans_collapse = 1
net.ipv4.ip_default_ttl = 64
net.ipv4.ip_no_pmtu_disc = 0
net.ipv4.ip_nonlocal_bind = 0
net.ipv4.tcp_syn_retries = 5
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_max_orphans = 8192
net.ipv4.tcp_max_tw_buckets = 8192
net.ipv4.ip_dynaddr = 0
net.ipv4.tcp_keepalive_time = 7200
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_retries1 = 3
net.ipv4.tcp_retries2 = 15
net.ipv4.tcp_fin_timeout = 60
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_abort_on_overflow = 0
net.ipv4.tcp_stdurg = 0
net.ipv4.tcp_rfc1337 = 0
net.ipv4.tcp_max_syn_backlog = 128
net.ipv4.ip_local_port_range = 32768 61000
net.ipv4.ip_local_reserved_ports =
net.ipv4.igmp_max_memberships = 20
net.ipv4.igmp_max_msf = 10
net.ipv4.inet_peer_threshold = 65664
net.ipv4.inet_peer_minttl = 120
net.ipv4.inet_peer_maxttl = 600
net.ipv4.inet_peer_gc_mintime = 10
net.ipv4.inet_peer_gc_maxtime = 120
net.ipv4.tcp_orphan_retries = 0
net.ipv4.tcp_fack = 1
net.ipv4.tcp_reordering = 3
net.ipv4.tcp_ecn = 2
net.ipv4.tcp_dsack = 1
net.ipv4.tcp_mem = 7014 9354 14028
net.ipv4.tcp_wmem = 4096 16384 299328
net.ipv4.tcp_rmem = 4096 87380 299328
net.ipv4.tcp_app_win = 31
net.ipv4.tcp_adv_win_scale = 2
net.ipv4.tcp_tw_reuse = 0
net.ipv4.tcp_frto = 2
net.ipv4.tcp_frto_response = 0
net.ipv4.tcp_low_latency = 0
net.ipv4.tcp_no_metrics_save = 0
net.ipv4.tcp_moderate_rcvbuf = 1
net.ipv4.tcp_tso_win_divisor = 3
net.ipv4.tcp_congestion_control = cubic
net.ipv4.tcp_abc = 0
net.ipv4.tcp_mtu_probing = 0
net.ipv4.tcp_base_mss = 512
net.ipv4.tcp_workaround_signed_windows = 0
net.ipv4.tcp_slow_start_after_idle = 1
net.ipv4.tcp_available_congestion_control = cubic reno
net.ipv4.tcp_allowed_congestion_control = cubic reno
net.ipv4.tcp_max_ssthresh = 0
net.ipv4.tcp_cookie_size = 0
net.ipv4.tcp_thin_linear_timeouts = 0
net.ipv4.tcp_thin_dupack = 0
net.ipv4.udp_mem = 7014 9354 14028
net.ipv4.udp_rmem_min = 4096
net.ipv4.udp_wmem_min = 4096
net.ipv4.conf.all.forwarding = 0
net.ipv4.conf.all.mc_forwarding = 0
net.ipv4.conf.all.accept_redirects = 1
net.ipv4.conf.all.secure_redirects = 1
net.ipv4.conf.all.shared_media = 1
net.ipv4.conf.all.rp_filter = 0
net.ipv4.conf.all.send_redirects = 1
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.accept_local = 0
net.ipv4.conf.all.src_valid_mark = 0
net.ipv4.conf.all.proxy_arp = 0
net.ipv4.conf.all.medium_id = 0
net.ipv4.conf.all.bootp_relay = 0
net.ipv4.conf.all.log_martians = 0
net.ipv4.conf.all.tag = 0
net.ipv4.conf.all.arp_filter = 0
net.ipv4.conf.all.arp_announce = 0
net.ipv4.conf.all.arp_ignore = 0
net.ipv4.conf.all.arp_accept = 0
net.ipv4.conf.all.arp_notify = 0
net.ipv4.conf.all.proxy_arp_pvlan = 0
net.ipv4.conf.all.disable_xfrm = 0
net.ipv4.conf.all.disable_policy = 0
net.ipv4.conf.all.force_igmp_version = 0
net.ipv4.conf.all.promote_secondaries = 0
net.ipv4.conf.default.forwarding = 0
net.ipv4.conf.default.mc_forwarding = 0
net.ipv4.conf.default.accept_redirects = 1
net.ipv4.conf.default.secure_redirects = 1
net.ipv4.conf.default.shared_media = 1
net.ipv4.conf.default.rp_filter = 0
net.ipv4.conf.default.send_redirects = 1
net.ipv4.conf.default.accept_source_route = 1
net.ipv4.conf.default.accept_local = 0
net.ipv4.conf.default.src_valid_mark = 0
net.ipv4.conf.default.proxy_arp = 0
net.ipv4.conf.default.medium_id = 0
net.ipv4.conf.default.bootp_relay = 0
net.ipv4.conf.default.log_martians = 0
net.ipv4.conf.default.tag = 0
net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.default.arp_announce = 0
net.ipv4.conf.default.arp_ignore = 0
net.ipv4.conf.default.arp_accept = 0
net.ipv4.conf.default.arp_notify = 0
net.ipv4.conf.default.proxy_arp_pvlan = 0
net.ipv4.conf.default.disable_xfrm = 0
net.ipv4.conf.default.disable_policy = 0
net.ipv4.conf.default.force_igmp_version = 0
net.ipv4.conf.default.promote_secondaries = 0
net.ipv4.conf.lo.forwarding = 0
net.ipv4.conf.lo.mc_forwarding = 0
net.ipv4.conf.lo.accept_redirects = 1
net.ipv4.conf.lo.secure_redirects = 1
net.ipv4.conf.lo.shared_media = 1
net.ipv4.conf.lo.rp_filter = 0
net.ipv4.conf.lo.send_redirects = 1
net.ipv4.conf.lo.accept_source_route = 1
net.ipv4.conf.lo.accept_local = 0
net.ipv4.conf.lo.src_valid_mark = 0
net.ipv4.conf.lo.proxy_arp = 0
net.ipv4.conf.lo.medium_id = 0
net.ipv4.conf.lo.bootp_relay = 0
net.ipv4.conf.lo.log_martians = 0
net.ipv4.conf.lo.tag = 0
net.ipv4.conf.lo.arp_filter = 0
net.ipv4.conf.lo.arp_announce = 0
net.ipv4.conf.lo.arp_ignore = 0
net.ipv4.conf.lo.arp_accept = 0
net.ipv4.conf.lo.arp_notify = 0
net.ipv4.conf.lo.proxy_arp_pvlan = 0
net.ipv4.conf.lo.disable_xfrm = 1
net.ipv4.conf.lo.disable_policy = 1
net.ipv4.conf.lo.force_igmp_version = 0
net.ipv4.conf.lo.promote_secondaries = 0
net.ipv4.conf.eth0.forwarding = 0
net.ipv4.conf.eth0.mc_forwarding = 0
net.ipv4.conf.eth0.accept_redirects = 1
net.ipv4.conf.eth0.secure_redirects = 1
net.ipv4.conf.eth0.shared_media = 1
net.ipv4.conf.eth0.rp_filter = 0[ 2414.137398] process `sysctl' is using deprecated sysctl (syscall) net.ipv6.neigh.default.retrans_time; Use net.ipv6.neigh.default.retrans_time_ms instead.
net.ipv4.conf.eth0.send_redirects = 1
net.ipv4.conf.eth0.accept_source_route = 1
net.ipv4.conf.eth0.accept_local = 0
net.ipv4.conf.eth0.src_valid_mark = 0
net.ipv4.conf.eth0.proxy_arp = 0
net.ipv4.conf.eth0.medium_id = 0
net.ipv4.conf.eth0.bootp_relay = 0
net.ipv4.conf.eth0.log_martians = 0
net.ipv4.conf.eth0.tag = 0
net.ipv4.conf.eth0.arp_filter = 0
net.ipv4.conf.eth0.arp_announce = 0
net.ipv4.conf.eth0.arp_ignore = 0
net.ipv4.conf.eth0.arp_accept = 0
net.ipv4.conf.eth0.arp_notify = 0
net.ipv4.conf.eth0.proxy_arp_pvlan = 0
net.ipv4.conf.eth0.disable_xfrm = 0
net.ipv4.conf.eth0.disable_policy = 0
net.ipv4.conf.eth0.force_igmp_version = 0
net.ipv4.conf.eth0.promote_secondaries = 0
net.ipv4.conf.sit0.forwarding = 0
net.ipv4.conf.sit0.mc_forwarding = 0
net.ipv4.conf.sit0.accept_redirects = 1
net.ipv4.conf.sit0.secure_redirects = 1
net.ipv4.conf.sit0.shared_media = 1
net.ipv4.conf.sit0.rp_filter = 0
net.ipv4.conf.sit0.send_redirects = 1
net.ipv4.conf.sit0.accept_source_route = 1
net.ipv4.conf.sit0.accept_local = 0
net.ipv4.conf.sit0.src_valid_mark = 0
net.ipv4.conf.sit0.proxy_arp = 0
net.ipv4.conf.sit0.medium_id = 0
net.ipv4.conf.sit0.bootp_relay = 0
net.ipv4.conf.sit0.log_martians = 0
net.ipv4.conf.sit0.tag = 0
net.ipv4.conf.sit0.arp_filter = 0
net.ipv4.conf.sit0.arp_announce = 0
net.ipv4.conf.sit0.arp_ignore = 0
net.ipv4.conf.sit0.arp_accept = 0
net.ipv4.conf.sit0.arp_notify = 0
net.ipv4.conf.sit0.proxy_arp_pvlan = 0
net.ipv4.conf.sit0.disable_xfrm = 0
net.ipv4.conf.sit0.disable_policy = 0
net.ipv4.conf.sit0.force_igmp_version = 0
net.ipv4.conf.sit0.promote_secondaries = 0
net.ipv4.ip_forward = 0
net.ipv4.xfrm4_gc_thresh = 32768
net.ipv4.ipfrag_high_thresh = 262144
net.ipv4.ipfrag_low_thresh = 196608
net.ipv4.ipfrag_time = 30
net.ipv4.icmp_echo_ignore_all = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.icmp_errors_use_inbound_ifaddr = 0
net.ipv4.icmp_ratelimit = 1000
net.ipv4.icmp_ratemask = 6168
net.ipv4.rt_cache_rebuild_count = 4
net.ipv4.ping_group_range = 1 0
net.ipv4.ipfrag_secret_interval = 600
net.ipv4.ipfrag_max_dist = 64
net.ipv6.neigh.default.mcast_solicit = 3
net.ipv6.neigh.default.ucast_solicit = 3
net.ipv6.neigh.default.app_solicit = 0
net.ipv6.neigh.default.retrans_time = 200
net.ipv6.neigh.default.base_reachable_time = 30
net.ipv6.neigh.default.delay_first_probe_time = 5
net.ipv6.neigh.default.gc_stale_time = 60
net.ipv6.neigh.default.unres_qlen = 3
net.ipv6.neigh.default.proxy_qlen = 64
net.ipv6.neigh.default.anycast_delay = 100
net.ipv6.neigh.default.proxy_delay = 80
net.ipv6.neigh.default.locktime = 0
net.ipv6.neigh.default.retrans_time_ms = 1000
net.ipv6.neigh.default.base_reachable_time_ms = 30000
net.ipv6.neigh.default.gc_interval = 30
net.ipv6.neigh.default.gc_thresh1 = 128
net.ipv6.neigh.default.gc_thresh2 = 512
net.ipv6.neigh.default.gc_thresh3 = 1024
net.ipv6.neigh.lo.mcast_solicit = 3
net.ipv6.neigh.lo.ucast_solicit = 3
net.ipv6.neigh.lo.app_solicit = 0
net.ipv6.neigh.lo.retrans_time = 200
net.ipv6.neigh.lo.base_reachable_time = 30
net.ipv6.neigh.lo.delay_first_probe_time = 5
net.ipv6.neigh.lo.gc_stale_time = 60
net.ipv6.neigh.lo.unres_qlen = 3
net.ipv6.neigh.lo.proxy_qlen = 64
net.ipv6.neigh.lo.anycast_delay = 100
net.ipv6.neigh.lo.proxy_delay = 80
net.ipv6.neigh.lo.locktime = 0
net.ipv6.neigh.lo.retrans_time_ms = 1000
net.ipv6.neigh.lo.base_reachable_time_ms = 30000
net.ipv6.neigh.eth0.mcast_solicit = 3
net.ipv6.neigh.eth0.ucast_solicit = 3
net.ipv6.neigh.eth0.app_solicit = 0
net.ipv6.neigh.eth0.retrans_time = 200
net.ipv6.neigh.eth0.base_reachable_time = 30
net.ipv6.neigh.eth0.delay_first_probe_time = 5
net.ipv6.neigh.eth0.gc_stale_time = 60
net.ipv6.neigh.eth0.unres_qlen = 3
net.ipv6.neigh.eth0.proxy_qlen = 64
net.ipv6.neigh.eth0.anycast_delay = 100
net.ipv6.neigh.eth0.proxy_delay = 80
net.ipv6.neigh.eth0.locktime = 0
net.ipv6.neigh.eth0.retrans_time_ms = 1000
net.ipv6.neigh.eth0.base_reachable_time_ms = 30000
net.ipv6.neigh.sit0.mcast_solicit = 3
net.ipv6.neigh.sit0.ucast_solicit = 3
net.ipv6.neigh.sit0.app_solicit = 0
net.ipv6.neigh.sit0.retrans_time = 200
net.ipv6.neigh.sit0.base_reachable_time = 30
net.ipv6.neigh.sit0.delay_first_probe_time = 5
net.ipv6.neigh.sit0.gc_stale_time = 60
net.ipv6.neigh.sit0.unres_qlen = 3
net.ipv6.neigh.sit0.proxy_qlen = 64
net.ipv6.neigh.sit0.anycast_delay = 100
net.ipv6.neigh.sit0.proxy_delay = 80
net.ipv6.neigh.sit0.locktime = 0
net.ipv6.neigh.sit0.retrans_time_ms = 1000
net.ipv6.neigh.sit0.base_reachable_time_ms = 30000
net.ipv6.xfrm6_gc_thresh = 1024
net.ipv6.conf.all.forwarding = 0
net.ipv6.conf.all.hop_limit = 64
net.ipv6.conf.all.mtu = 1280
net.ipv6.conf.all.accept_ra = 1
net.ipv6.conf.all.accept_redirects = 1
net.ipv6.conf.all.autoconf = 1
net.ipv6.conf.all.dad_transmits = 1
net.ipv6.conf.all.router_solicitations = 3
net.ipv6.conf.all.router_solicitation_interval = 4
net.ipv6.conf.all.router_solicitation_delay = 1
net.ipv6.conf.all.force_mld_version = 0
net.ipv6.conf.all.max_addresses = 16
net.ipv6.conf.all.accept_ra_defrtr = 1
net.ipv6.conf.all.accept_ra_pinfo = 1
net.ipv6.conf.all.proxy_ndp = 0
net.ipv6.conf.all.accept_source_route = 0
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.all.accept_dad = 1
net.ipv6.conf.all.force_tllao = 0
net.ipv6.conf.default.forwarding = 0
net.ipv6.conf.default.hop_limit = 64
net.ipv6.conf.default.mtu = 1280
net.ipv6.conf.default.accept_ra = 1
net.ipv6.conf.default.accept_redirects = 1
net.ipv6.conf.default.autoconf = 1
net.ipv6.conf.default.dad_transmits = 1
net.ipv6.conf.default.router_solicitations = 3
net.ipv6.conf.default.router_solicitation_interval = 4
net.ipv6.conf.default.router_solicitation_delay = 1
net.ipv6.conf.default.force_mld_version = 0
net.ipv6.conf.default.max_addresses = 16
net.ipv6.conf.default.accept_ra_defrtr = 1
net.ipv6.conf.default.accept_ra_pinfo = 1
net.ipv6.conf.default.proxy_ndp = 0
net.ipv6.conf.default.accept_source_route = 0
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.default.accept_dad = 1
net.ipv6.conf.default.force_tllao = 0
net.ipv6.conf.lo.forwarding = 0
net.ipv6.conf.lo.hop_limit = 64
net.ipv6.conf.lo.mtu = 16436
net.ipv6.conf.lo.accept_ra = 1
net.ipv6.conf.lo.accept_redirects = 1
net.ipv6.conf.lo.autoconf = 1
net.ipv6.conf.lo.dad_transmits = 1
net.ipv6.conf.lo.router_solicitations = 3
net.ipv6.conf.lo.router_solicitation_interval = 4
net.ipv6.conf.lo.router_solicitation_delay = 1
net.ipv6.conf.lo.force_mld_version = 0
net.ipv6.conf.lo.max_addresses = 16
net.ipv6.conf.lo.accept_ra_defrtr = 1
net.ipv6.conf.lo.accept_ra_pinfo = 1
net.ipv6.conf.lo.proxy_ndp = 0
net.ipv6.conf.lo.accept_source_route = 0
net.ipv6.conf.lo.disable_ipv6 = 1
net.ipv6.conf.lo.accept_dad = -1
net.ipv6.conf.lo.force_tllao = 0
net.ipv6.conf.eth0.forwarding = 0
net.ipv6.conf.eth0.hop_limit = 64
net.ipv6.conf.eth0.mtu = 1500
net.ipv6.conf.eth0.accept_ra = 1
net.ipv6.conf.eth0.accept_redirects = 1
net.ipv6.conf.eth0.autoconf = 1
net.ipv6.conf.eth0.dad_transmits = 1
net.ipv6.conf.eth0.router_solicitations = 3
net.ipv6.conf.eth0.router_solicitation_interval = 4
net.ipv6.conf.eth0.router_solicitation_delay = 1
net.ipv6.conf.eth0.force_mld_version = 0
net.ipv6.conf.eth0.max_addresses = 16
net.ipv6.conf.eth0.accept_ra_defrtr = 1
net.ipv6.conf.eth0.accept_ra_pinfo = 1
net.ipv6.conf.eth0.proxy_ndp = 0
net.ipv6.conf.eth0.accept_source_route = 0
net.ipv6.conf.eth0.disable_ipv6 = 1
net.ipv6.conf.eth0.accept_dad = 1
net.ipv6.conf.eth0.force_tllao = 0
net.ipv6.conf.sit0.forwarding = 0
net.ipv6.conf.sit0.hop_limit = 64
net.ipv6.conf.sit0.mtu = 1480
net.ipv6.conf.sit0.accept_ra = 1
net.ipv6.conf.sit0.accept_redirects = 1
net.ipv6.conf.sit0.autoconf = 1
net.ipv6.conf.sit0.dad_transmits = 1
net.ipv6.conf.sit0.router_solicitations = 3
net.ipv6.conf.sit0.router_solicitation_interval = 4
net.ipv6.conf.sit0.router_solicitation_delay = 1
net.ipv6.conf.sit0.force_mld_version = 0
net.ipv6.conf.sit0.max_addresses = 16
net.ipv6.conf.sit0.accept_ra_defrtr = 1
net.ipv6.conf.sit0.accept_ra_pinfo = 1
net.ipv6.conf.sit0.proxy_ndp = 0
net.ipv6.conf.sit0.accept_source_route = 0
net.ipv6.conf.sit0.disable_ipv6 = 1
net.ipv6.conf.sit0.accept_dad = -1
net.ipv6.conf.sit0.force_tllao = 0
net.ipv6.ip6frag_high_thresh = 262144
net.ipv6.ip6frag_low_thresh = 196608
net.ipv6.ip6frag_time = 60
net.ipv6.route.gc_thresh = 1024
net.ipv6.route.max_size = 4096
net.ipv6.route.gc_min_interval = 0
net.ipv6.route.gc_timeout = 60
net.ipv6.route.gc_interval = 30
net.ipv6.route.gc_elasticity = 9
net.ipv6.route.mtu_expires = 600
net.ipv6.route.min_adv_mss = 1220
net.ipv6.route.gc_min_interval_ms = 500
net.ipv6.icmp.ratelimit = 1000
net.ipv6.bindv6only = 0
net.ipv6.ip6frag_secret_interval = 600
net.ipv6.mld_max_msf = 64
net.unix.max_dgram_qlen = 10
sh-#
接下来我们以IPv6为例,说明如何在系统运行时配置内核参数.
通过如下结果,知道当前IPv6是disable的,
sh-# cat /proc/sys/net/ipv6/conf/all/disable_ipv6
1
sh-#
sh-# ifconfig
eth0 Link encap:Ethernet HWaddr 00:00:00:00:FF:95
inet addr:192.168.0.156 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:530 errors:0 dropped:322 overruns:0 frame:0
TX packets:94 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:69477 (67.8 Kb) TX bytes:14612 (14.2 Kb)
Interrupt:40 Base address:0x2000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:192 (192.0 b) TX bytes:192 (192.0 b)
sh-#
所以接下来来enable IPv6了,
方法1:
sh-# echo 0 > /proc/sys/net/ipv6/conf/all/disable_ipv6
[ 830.557187] ADDRCONF(NETDEV_UP): sit0: link is not ready
sh-#
sh-# ifconfig
eth0 Link encap:Ethernet HWaddr 00:00:00:00:FF:95
inet addr:192.168.0.156 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::200:ff:fe00:ff95/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:672 errors:0 dropped:418 overruns:0 frame:0
TX packets:124 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:86129 (84.1 Kb) TX bytes:18590 (18.1 Kb)
Interrupt:40 Base address:0x2000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:192 (192.0 b) TX bytes:192 (192.0 b)
sh-#
sh-# ping6 -I eth0 -c 4 fe80::200:ff:fe00:ff95
PING fe80::200:ff:fe00:ff95(fe80::200:ff:fe00:ff95) from fe80::200:ff:fe00:ff95 eth0: 56 data bytes
64 bytes from fe80::200:ff:fe00:ff95: icmp_seq=1 ttl=64 time=0.060 ms
64 bytes from fe80::200:ff:fe00:ff95: icmp_seq=2 ttl=64 time=0.059 ms
64 bytes from fe80::200:ff:fe00:ff95: icmp_seq=3 ttl=64 time=0.061 ms
64 bytes from fe80::200:ff:fe00:ff95: icmp_seq=4 ttl=64 time=0.060 ms
--- fe80::200:ff:fe00:ff95 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.059/0.060/0.061/0.000 ms
sh-#
方法2:
sh-# sysctl -w net.ipv6.conf.all.disable_ipv6=0
[ 946.780791] ADDRCONF(NETDEV_UP): sit0: link is not ready
net.ipv6.conf.all.disable_ipv6 = 0
sh-#
方法3:
以上两种方法均是在系统运行时临时性的修改方法。
如果要想让配置每次系统启动时自动载入,那么就要修改/etc/sysctl.conf这个档案，
这样系统启动时就会自动载入/etc/sysctl.conf里的设定。
sh-# cat /etc/sysctl.conf
net.ipv4.tcp_window_scaling = 6
sh-# touch /tmp/sysctl.conf
sh-# cat /tmp/sysctl.conf
net.ipv6.conf.all.disable_ipv6 = 0
sh-#
sh-# sysctl -p /tmp/sysctl.conf
[ 1584.745895] ADDRCONF(NETDEV_UP): sit0: link is not ready
net.ipv6.conf.all.disable_ipv6 = 0
sh-# cat /proc/sys/net/ipv6/conf/all/disable_ipv6
0
sh-#
从以上，可以看到有大量的内核参数。
这些内核参数的值，恰恰反映了当前内核的实时状态。
所以了解这些内核参数的含义，对分析和解决问题将会很有帮助。
本篇也只是作为相关内容的入门，后面随着学习的深入会将更多的心得陆续补充上来。
欢迎大家一起交流学习。
