刚发现一个linux在线文档库。很好很强大。

1.网址: http://www.mjmwired.net 

 

2.比如查看这个 proc.txt ,就在这里能找到。

http://www.mjmwired.net/kernel/Documentation/filesystems/proc.txt

 

内核参数解释全在这里了。不过,也可以下载内核完源代码,从/usr/src/linux/Documentation/proc.txt查看

下载内核从http://www.kernel.org/pub/linux/kernel/v2.6/

解压完后从这里打开:

linux-2.6.28/Documentation/filesystems/proc.txt    

 

3.此外,在filesystems下还有很多文档,比如ext4.txt,很详细,很全面,很有用。

 

4.这里提供一个2.6.28的完整proc.txt文档

注意linux系统管理技术手册 第二版   说的是  proc.txt  在  /usr/src/linux/Documentation/proc.txt  ,具体问题,具体分析吧。

------------------------------------------------------------------------------ T H E /proc F I L E S Y S T E M ------------------------------------------------------------------------------ /proc/sys Terrehon Bowden October 7 1999 Bodo Bauer 2.4.x update Jorge Nerin November 14 2000 ------------------------------------------------------------------------------ Version 1.3 Kernel version 2.2.12 Kernel version 2.4.0-test11-pre4 ------------------------------------------------------------------------------ Table of Contents ----------------- 0 Preface 0.1 Introduction/Credits 0.2 Legal Stuff 1 Collecting System Information 1.1 Process-Specific Subdirectories 1.2 Kernel data 1.3 IDE devices in /proc/ide 1.4 Networking info in /proc/net 1.5 SCSI info 1.6 Parallel port info in /proc/parport 1.7 TTY info in /proc/tty 1.8 Miscellaneous kernel statistics in /proc/stat 2 Modifying System Parameters 2.1 /proc/sys/fs - File system data 2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats 2.3 /proc/sys/kernel - general kernel parameters 2.4 /proc/sys/vm - The virtual memory subsystem 2.5 /proc/sys/dev - Device specific parameters 2.6 /proc/sys/sunrpc - Remote procedure calls 2.7 /proc/sys/net - Networking stuff 2.8 /proc/sys/net/ipv4 - IPV4 settings 2.9 Appletalk 2.10 IPX 2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem 2.12 /proc//oom_adj - Adjust the oom-killer score 2.13 /proc//oom_score - Display current oom-killer score 2.14 /proc//io - Display the IO accounting fields 2.15 /proc//coredump_filter - Core dump filtering settings 2.16 /proc//mountinfo - Information about mounts 2.17 /proc/sys/fs/epoll - Configuration options for the epoll interface ------------------------------------------------------------------------------ Preface ------------------------------------------------------------------------------ 0.1 Introduction/Credits ------------------------ This documentation is part of a soon (or so we hope) to be released book on the SuSE Linux distribution. As there is no complete documentation for the /proc file system and we've used many freely available sources to write these chapters, it seems only fair to give the work back to the Linux community. This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm afraid it's still far from complete, but we hope it will be useful. As far as we know, it is the first 'all-in-one' document about the /proc file system. It is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, SPARC, AXP, etc., features, you probably won't find what you are looking for. It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But additions and patches are welcome and will be added to this document if you mail them to Bodo. We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of other people for help compiling this documentation. We'd also like to extend a special thank you to Andi Kleen for documentation, which we relied on heavily to create this document, as well as the additional information he provided. Thanks to everybody else who contributed source or docs to the Linux kernel and helped create a great piece of software... :) If you have any comments, corrections or additions, please don't hesitate to contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this document. The latest version of this document is available online at http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version. If the above direction does not works for you, ypu could try the kernel mailing list at linux-kernel@vger.kernel.org and/or try to reach me at comandante@zaralinux.com. 0.2 Legal Stuff --------------- We don't guarantee the correctness of this document, and if you come to us complaining about how you screwed up your system because of incorrect documentation, we won't feel responsible... ------------------------------------------------------------------------------ CHAPTER 1: COLLECTING SYSTEM INFORMATION ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ In This Chapter ------------------------------------------------------------------------------ * Investigating the properties of the pseudo file system /proc and its ability to provide information on the running Linux system * Examining /proc's structure * Uncovering various information about the kernel and the processes running on the system ------------------------------------------------------------------------------ The proc file system acts as an interface to internal data structures in the kernel. It can be used to obtain information about the system and to change certain kernel parameters at runtime (sysctl). First, we'll take a look at the read-only parts of /proc. In Chapter 2, we show you how you can use /proc/sys to change settings. 1.1 Process-Specific Subdirectories ----------------------------------- The directory /proc contains (among other things) one subdirectory for each process running on the system, which is named after the process ID (PID). The link self points to the process reading the file system. Each process subdirectory has the entries listed in Table 1-1. Table 1-1: Process specific entries in /proc .............................................................................. File Content clear_refs Clears page referenced bits shown in smaps output cmdline Command line arguments cpu Current and last cpu in which it was executed (2.4)(smp) cwd Link to the current working directory environ Values of environment variables exe Link to the executable of this process fd Directory, which contains all file descriptors maps Memory maps to executables and library files (2.4) mem Memory held by this process root Link to the root directory of this process stat Process status statm Process memory status information status Process status in human readable form wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan smaps Extension based on maps, the rss size for each mapped file .............................................................................. For example, to get the status information of a process, all you have to do is read the file /proc/PID/status: >cat /proc/self/status Name: cat State: R (running) Pid: 5452 PPid: 743 TracerPid: 0 (2.4) Uid: 501 501 501 501 Gid: 100 100 100 100 Groups: 100 14 16 VmSize: 1112 kB VmLck: 0 kB VmRSS: 348 kB VmData: 24 kB VmStk: 12 kB VmExe: 8 kB VmLib: 1044 kB SigPnd: 0000000000000000 SigBlk: 0000000000000000 SigIgn: 0000000000000000 SigCgt: 0000000000000000 CapInh: 00000000fffffeff CapPrm: 0000000000000000 CapEff: 0000000000000000 This shows you nearly the same information you would get if you viewed it with the ps command. In fact, ps uses the proc file system to obtain its information. The statm file contains more detailed information about the process memory usage. Its seven fields are explained in Table 1-2. The stat file contains details information about the process itself. Its fields are explained in Table 1-3. Table 1-2: Contents of the statm files (as of 2.6.8-rc3) .............................................................................. Field Content size total program size (pages) (same as VmSize in status) resident size of memory portions (pages) (same as VmRSS in status) shared number of pages that are shared (i.e. backed by a file) trs number of pages that are 'code' (not including libs; broken, includes data segment) lrs number of pages of library (always 0 on 2.6) drs number of pages of data/stack (including libs; broken, includes library text) dt number of dirty pages (always 0 on 2.6) .............................................................................. Table 1-3: Contents of the stat files (as of 2.6.22-rc3) .............................................................................. Field Content pid process id tcomm filename of the executable state state (R is running, S is sleeping, D is sleeping in an uninterruptible wait, Z is zombie, T is traced or stopped) ppid process id of the parent process pgrp pgrp of the process sid session id tty_nr tty the process uses tty_pgrp pgrp of the tty flags task flags min_flt number of minor faults cmin_flt number of minor faults with child's maj_flt number of major faults cmaj_flt number of major faults with child's utime user mode jiffies stime kernel mode jiffies cutime user mode jiffies with child's cstime kernel mode jiffies with child's priority priority level nice nice level num_threads number of threads it_real_value (obsolete, always 0) start_time time the process started after system boot vsize virtual memory size rss resident set memory size rsslim current limit in bytes on the rss start_code address above which program text can run end_code address below which program text can run start_stack address of the start of the stack esp current value of ESP eip current value of EIP pending bitmap of pending signals (obsolete) blocked bitmap of blocked signals (obsolete) sigign bitmap of ignored signals (obsolete) sigcatch bitmap of catched signals (obsolete) wchan address where process went to sleep 0 (place holder) 0 (place holder) exit_signal signal to send to parent thread on exit task_cpu which CPU the task is scheduled on rt_priority realtime priority policy scheduling policy (man sched_setscheduler) blkio_ticks time spent waiting for block IO .............................................................................. 1.2 Kernel data --------------- Similar to the process entries, the kernel data files give information about the running kernel. The files used to obtain this information are contained in /proc and are listed in Table 1-4. Not all of these will be present in your system. It depends on the kernel configuration and the loaded modules, which files are there, and which are missing. Table 1-4: Kernel info in /proc .............................................................................. File Content apm Advanced power management info buddyinfo Kernel memory allocator information (see text) (2.5) bus Directory containing bus specific information cmdline Kernel command line cpuinfo Info about the CPU devices Available devices (block and character) dma Used DMS channels filesystems Supported filesystems driver Various drivers grouped here, currently rtc (2.4) execdomains Execdomains, related to security (2.4) fb Frame Buffer devices (2.4) fs File system parameters, currently nfs/exports (2.4) ide Directory containing info about the IDE subsystem interrupts Interrupt usage iomem Memory map (2.4) ioports I/O port usage irq Masks for irq to cpu affinity (2.4)(smp?) isapnp ISA PnP (Plug&Play) Info (2.4) kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) kmsg Kernel messages ksyms Kernel symbol table loadavg Load average of last 1, 5 & 15 minutes locks Kernel locks meminfo Memory info misc Miscellaneous modules List of loaded modules mounts Mounted filesystems net Networking info (see text) partitions Table of partitions known to the system pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, decoupled by lspci (2.4) rtc Real time clock scsi SCSI info (see text) slabinfo Slab pool info stat Overall statistics swaps Swap space utilization sys See chapter 2 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) tty Info of tty drivers uptime System uptime version Kernel version video bttv info of video resources (2.4) vmallocinfo Show vmalloced areas .............................................................................. You can, for example, check which interrupts are currently in use and what they are used for by looking in the file /proc/interrupts: > cat /proc/interrupts CPU0 0: 8728810 XT-PIC timer 1: 895 XT-PIC keyboard 2: 0 XT-PIC cascade 3: 531695 XT-PIC aha152x 4: 2014133 XT-PIC serial 5: 44401 XT-PIC pcnet_cs 8: 2 XT-PIC rtc 11: 8 XT-PIC i82365 12: 182918 XT-PIC PS/2 Mouse 13: 1 XT-PIC fpu 14: 1232265 XT-PIC ide0 15: 7 XT-PIC ide1 NMI: 0 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the output of a SMP machine): > cat /proc/interrupts CPU0 CPU1 0: 1243498 1214548 IO-APIC-edge timer 1: 8949 8958 IO-APIC-edge keyboard 2: 0 0 XT-PIC cascade 5: 11286 10161 IO-APIC-edge soundblaster 8: 1 0 IO-APIC-edge rtc 9: 27422 27407 IO-APIC-edge 3c503 12: 113645 113873 IO-APIC-edge PS/2 Mouse 13: 0 0 XT-PIC fpu 14: 22491 24012 IO-APIC-edge ide0 15: 2183 2415 IO-APIC-edge ide1 17: 30564 30414 IO-APIC-level eth0 18: 177 164 IO-APIC-level bttv NMI: 2457961 2457959 LOC: 2457882 2457881 ERR: 2155 NMI is incremented in this case because every timer interrupt generates a NMI (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. LOC is the local interrupt counter of the internal APIC of every CPU. ERR is incremented in the case of errors in the IO-APIC bus (the bus that connects the CPUs in a SMP system. This means that an error has been detected, the IO-APIC automatically retry the transmission, so it should not be a big problem, but you should read the SMP-FAQ. In 2.6.2* /proc/interrupts was expanded again. This time the goal was for /proc/interrupts to display every IRQ vector in use by the system, not just those considered 'most important'. The new vectors are: THR -- interrupt raised when a machine check threshold counter (typically counting ECC corrected errors of memory or cache) exceeds a configurable threshold. Only available on some systems. TRM -- a thermal event interrupt occurs when a temperature threshold has been exceeded for the CPU. This interrupt may also be generated when the temperature drops back to normal. SPU -- a spurious interrupt is some interrupt that was raised then lowered by some IO device before it could be fully processed by the APIC. Hence the APIC sees the interrupt but does not know what device it came from. For this case the APIC will generate the interrupt with a IRQ vector of 0xff. This might also be generated by chipset bugs. RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are sent from one CPU to another per the needs of the OS. Typically, their statistics are used by kernel developers and interested users to determine the occurance of interrupt of the given type. The above IRQ vectors are displayed only when relevent. For example, the threshold vector does not exist on x86_64 platforms. Others are suppressed when the system is a uniprocessor. As of this writing, only i386 and x86_64 platforms support the new IRQ vector displays. Of some interest is the introduction of the /proc/irq directory to 2.4. It could be used to set IRQ to CPU affinity, this means that you can "hook" an IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and prof_cpu_mask. For example > ls /proc/irq/ 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 1 11 13 15 17 19 3 5 7 9 default_smp_affinity > ls /proc/irq/0/ smp_affinity smp_affinity is a bitmask, in which you can specify which CPUs can handle the IRQ, you can set it by doing: > echo 1 > /proc/irq/10/smp_affinity This means that only the first CPU will handle the IRQ, but you can also echo 5 which means that only the first and fourth CPU can handle the IRQ. The contents of each smp_affinity file is the same by default: > cat /proc/irq/0/smp_affinity ffffffff The default_smp_affinity mask applies to all non-active IRQs, which are the IRQs which have not yet been allocated/activated, and hence which lack a /proc/irq/[0-9]* directory. prof_cpu_mask specifies which CPUs are to be profiled by the system wide profiler. Default value is ffffffff (all cpus). The way IRQs are routed is handled by the IO-APIC, and it's Round Robin between all the CPUs which are allowed to handle it. As usual the kernel has more info than you and does a better job than you, so the defaults are the best choice for almost everyone. There are three more important subdirectories in /proc: net, scsi, and sys. The general rule is that the contents, or even the existence of these directories, depend on your kernel configuration. If SCSI is not enabled, the directory scsi may not exist. The same is true with the net, which is there only when networking support is present in the running kernel. The slabinfo file gives information about memory usage at the slab level. Linux uses slab pools for memory management above page level in version 2.2. Commonly used objects have their own slab pool (such as network buffers, directory cache, and so on). .............................................................................. > cat /proc/buddyinfo Node 0, zone DMA 0 4 5 4 4 3 ... Node 0, zone Normal 1 0 0 1 101 8 ... Node 0, zone HighMem 2 0 0 1 1 0 ... Memory fragmentation is a problem under some workloads, and buddyinfo is a useful tool for helping diagnose these problems. Buddyinfo will give you a clue as to how big an area you can safely allocate, or why a previous allocation failed. Each column represents the number of pages of a certain order which are available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE available in ZONE_NORMAL, etc... .............................................................................. meminfo: Provides information about distribution and utilization of memory. This varies by architecture and compile options. The following is from a 16GB PIII, which has highmem enabled. You may not have all of these fields. > cat /proc/meminfo MemTotal: 16344972 kB MemFree: 13634064 kB Buffers: 3656 kB Cached: 1195708 kB SwapCached: 0 kB Active: 891636 kB Inactive: 1077224 kB HighTotal: 15597528 kB HighFree: 13629632 kB LowTotal: 747444 kB LowFree: 4432 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 968 kB Writeback: 0 kB AnonPages: 861800 kB Mapped: 280372 kB Slab: 284364 kB SReclaimable: 159856 kB SUnreclaim: 124508 kB PageTables: 24448 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 7669796 kB Committed_AS: 100056 kB VmallocTotal: 112216 kB VmallocUsed: 428 kB VmallocChunk: 111088 kB MemTotal: Total usable ram (i.e. physical ram minus a few reserved bits and the kernel binary code) MemFree: The sum of LowFree+HighFree Buffers: Relatively temporary storage for raw disk blocks shouldn't get tremendously large (20MB or so) Cached: in-memory cache for files read from the disk (the pagecache). Doesn't include SwapCached SwapCached: Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it doesn't need to be swapped out AGAIN because it is already in the swapfile. This saves I/O) Active: Memory that has been used more recently and usually not reclaimed unless absolutely necessary. Inactive: Memory which has been less recently used. It is more eligible to be reclaimed for other purposes HighTotal: HighFree: Highmem is all memory above ~860MB of physical memory Highmem areas are for use by userspace programs, or for the pagecache. The kernel must use tricks to access this memory, making it slower to access than lowmem. LowTotal: LowFree: Lowmem is memory which can be used for everything that highmem can be used for, but it is also available for the kernel's use for its own data structures. Among many other things, it is where everything from the Slab is allocated. Bad things happen when you're out of lowmem. SwapTotal: total amount of swap space available SwapFree: Memory which has been evicted from RAM, and is temporarily on the disk Dirty: Memory which is waiting to get written back to the disk Writeback: Memory which is actively being written back to the disk AnonPages: Non-file backed pages mapped into userspace page tables Mapped: files which have been mmaped, such as libraries Slab: in-kernel data structures cache SReclaimable: Part of Slab, that might be reclaimed, such as caches SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure PageTables: amount of memory dedicated to the lowest level of page tables. NFS_Unstable: NFS pages sent to the server, but not yet committed to stable storage Bounce: Memory used for block device "bounce buffers" WritebackTmp: Memory used by FUSE for temporary writeback buffers CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), this is the total amount of memory currently available to be allocated on the system. This limit is only adhered to if strict overcommit accounting is enabled (mode 2 in 'vm.overcommit_memory'). The CommitLimit is calculated with the following formula: CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap For example, on a system with 1G of physical RAM and 7G of swap with a `vm.overcommit_ratio` of 30 it would yield a CommitLimit of 7.3G. For more details, see the memory overcommit documentation in vm/overcommit-accounting. Committed_AS: The amount of memory presently allocated on the system. The committed memory is a sum of all of the memory which has been allocated by processes, even if it has not been "used" by them as of yet. A process which malloc()'s 1G of memory, but only touches 300M of it will only show up as using 300M of memory even if it has the address space allocated for the entire 1G. This 1G is memory which has been "committed" to by the VM and can be used at any time by the allocating application. With strict overcommit enabled on the system (mode 2 in 'vm.overcommit_memory'), allocations which would exceed the CommitLimit (detailed above) will not be permitted. This is useful if one needs to guarantee that processes will not fail due to lack of memory once that memory has been successfully allocated. VmallocTotal: total size of vmalloc memory area VmallocUsed: amount of vmalloc area which is used VmallocChunk: largest contigious block of vmalloc area which is free .............................................................................. vmallocinfo: Provides information about vmalloced/vmaped areas. One line per area, containing the virtual address range of the area, size in bytes, caller information of the creator, and optional information depending on the kind of area : pages=nr number of pages phys=addr if a physical address was specified ioremap I/O mapping (ioremap() and friends) vmalloc vmalloc() area vmap vmap()ed pages user VM_USERMAP area vpages buffer for pages pointers was vmalloced (huge area) N=nr (Only on NUMA kernels) Number of pages allocated on memory node > cat /proc/vmallocinfo 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... phys=7fee8000 ioremap 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... phys=7fee7000 ioremap 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... pages=2 vmalloc N1=2 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... /0x130 [x_tables] pages=4 vmalloc N0=4 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... pages=14 vmalloc N2=14 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... pages=4 vmalloc N1=4 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... pages=2 vmalloc N1=2 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... pages=10 vmalloc N0=10 1.3 IDE devices in /proc/ide ---------------------------- The subdirectory /proc/ide contains information about all IDE devices of which the kernel is aware. There is one subdirectory for each IDE controller, the file drivers and a link for each IDE device, pointing to the device directory in the controller specific subtree. The file drivers contains general information about the drivers used for the IDE devices: > cat /proc/ide/drivers ide-cdrom version 4.53 ide-disk version 1.08 More detailed information can be found in the controller specific subdirectories. These are named ide0, ide1 and so on. Each of these directories contains the files shown in table 1-5. Table 1-5: IDE controller info in /proc/ide/ide? .............................................................................. File Content channel IDE channel (0 or 1) config Configuration (only for PCI/IDE bridge) mate Mate name model Type/Chipset of IDE controller .............................................................................. Each device connected to a controller has a separate subdirectory in the controllers directory. The files listed in table 1-6 are contained in these directories. Table 1-6: IDE device information .............................................................................. File Content cache The cache capacity Capacity of the medium (in 512Byte blocks) driver driver and version geometry physical and logical geometry identify device identify block media media type model device identifier settings device setup smart_thresholds IDE disk management thresholds smart_values IDE disk management values .............................................................................. The most interesting file is settings. This file contains a nice overview of the drive parameters: # cat /proc/ide/ide0/hda/settings name value min max mode ---- ----- --- --- ---- bios_cyl 526 0 65535 rw bios_head 255 0 255 rw bios_sect 63 0 63 rw breada_readahead 4 0 127 rw bswap 0 0 1 r file_readahead 72 0 2097151 rw io_32bit 0 0 3 rw keepsettings 0 0 1 rw max_kb_per_request 122 1 127 rw multcount 0 0 8 rw nice1 1 0 1 rw nowerr 0 0 1 rw pio_mode write-only 0 255 w slow 0 0 1 rw unmaskirq 0 0 1 rw using_dma 0 0 1 rw 1.4 Networking info in /proc/net -------------------------------- The subdirectory /proc/net follows the usual pattern. Table 1-6 shows the additional values you get for IP version 6 if you configure the kernel to support this. Table 1-7 lists the files and their meaning. Table 1-6: IPv6 info in /proc/net .............................................................................. File Content udp6 UDP sockets (IPv6) tcp6 TCP sockets (IPv6) raw6 Raw device statistics (IPv6) igmp6 IP multicast addresses, which this host joined (IPv6) if_inet6 List of IPv6 interface addresses ipv6_route Kernel routing table for IPv6 rt6_stats Global IPv6 routing tables statistics sockstat6 Socket statistics (IPv6) snmp6 Snmp data (IPv6) .............................................................................. Table 1-7: Network info in /proc/net .............................................................................. File Content arp Kernel ARP table dev network devices with statistics dev_mcast the Layer2 multicast groups a device is listening too (interface index, label, number of references, number of bound addresses). dev_stat network device status ip_fwchains Firewall chain linkage ip_fwnames Firewall chain names ip_masq Directory containing the masquerading tables ip_masquerade Major masquerading table netstat Network statistics raw raw device statistics route Kernel routing table rpc Directory containing rpc info rt_cache Routing cache snmp SNMP data sockstat Socket statistics tcp TCP sockets tr_rif Token ring RIF routing table udp UDP sockets unix UNIX domain sockets wireless Wireless interface data (Wavelan etc) igmp IP multicast addresses, which this host joined psched Global packet scheduler parameters. netlink List of PF_NETLINK sockets ip_mr_vifs List of multicast virtual interfaces ip_mr_cache List of multicast routing cache .............................................................................. You can use this information to see which network devices are available in your system and how much traffic was routed over those devices: > cat /proc/net/dev Inter-|Receive |[... face |bytes packets errs drop fifo frame compressed multicast|[... lo: 908188 5596 0 0 0 0 0 0 [... ppp0:15475140 20721 410 0 0 410 0 0 [... eth0: 614530 7085 0 0 0 0 0 1 [... ...] Transmit ...] bytes packets errs drop fifo colls carrier compressed ...] 908188 5596 0 0 0 0 0 0 ...] 1375103 17405 0 0 0 0 0 0 ...] 1703981 5535 0 0 0 3 0 0 In addition, each Channel Bond interface has it's own directory. For example, the bond0 device will have a directory called /proc/net/bond0/. It will contain information that is specific to that bond, such as the current slaves of the bond, the link status of the slaves, and how many times the slaves link has failed. 1.5 SCSI info ------------- If you have a SCSI host adapter in your system, you'll find a subdirectory named after the driver for this adapter in /proc/scsi. You'll also see a list of all recognized SCSI devices in /proc/scsi: >cat /proc/scsi/scsi Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: IBM Model: DGHS09U Rev: 03E0 Type: Direct-Access ANSI SCSI revision: 03 Host: scsi0 Channel: 00 Id: 06 Lun: 00 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 Type: CD-ROM ANSI SCSI revision: 02 The directory named after the driver has one file for each adapter found in the system. These files contain information about the controller, including the used IRQ and the IO address range. The amount of information shown is dependent on the adapter you use. The example shows the output for an Adaptec AHA-2940 SCSI adapter: > cat /proc/scsi/aic7xxx/0 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 Compile Options: TCQ Enabled By Default : Disabled AIC7XXX_PROC_STATS : Disabled AIC7XXX_RESET_DELAY : 5 Adapter Configuration: SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter Ultra Wide Controller PCI MMAPed I/O Base: 0xeb001000 Adapter SEEPROM Config: SEEPROM found and used. Adaptec SCSI BIOS: Enabled IRQ: 10 SCBs: Active 0, Max Active 2, Allocated 15, HW 16, Page 255 Interrupts: 160328 BIOS Control Word: 0x18b6 Adapter Control Word: 0x005b Extended Translation: Enabled Disconnect Enable Flags: 0xffff Ultra Enable Flags: 0x0001 Tag Queue Enable Flags: 0x0000 Ordered Queue Tag Flags: 0x0000 Default Tag Queue Depth: 8 Tagged Queue By Device array for aic7xxx host instance 0: {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} Actual queue depth per device for aic7xxx host instance 0: {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} Statistics: (scsi0:0:0:0) Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) Total transfers 160151 (74577 reads and 85574 writes) (scsi0:0:6:0) Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) Total transfers 0 (0 reads and 0 writes) 1.6 Parallel port info in /proc/parport --------------------------------------- The directory /proc/parport contains information about the parallel ports of your system. It has one subdirectory for each port, named after the port number (0,1,2,...). These directories contain the four files shown in Table 1-8. Table 1-8: Files in /proc/parport .............................................................................. File Content autoprobe Any IEEE-1284 device ID information that has been acquired. devices list of the device drivers using that port. A + will appear by the name of the device currently using the port (it might not appear against any). hardware Parallel port's base address, IRQ line and DMA channel. irq IRQ that parport is using for that port. This is in a separate file to allow you to alter it by writing a new value in (IRQ number or none). .............................................................................. 1.7 TTY info in /proc/tty ------------------------- Information about the available and actually used tty's can be found in the directory /proc/tty.You'll find entries for drivers and line disciplines in this directory, as shown in Table 1-9. Table 1-9: Files in /proc/tty .............................................................................. File Content drivers list of drivers and their usage ldiscs registered line disciplines driver/serial usage statistic and status of single tty lines .............................................................................. To see which tty's are currently in use, you can simply look into the file /proc/tty/drivers: > cat /proc/tty/drivers pty_slave /dev/pts 136 0-255 pty:slave pty_master /dev/ptm 128 0-255 pty:master pty_slave /dev/ttyp 3 0-255 pty:slave pty_master /dev/pty 2 0-255 pty:master serial /dev/cua 5 64-67 serial:callout serial /dev/ttyS 4 64-67 serial /dev/tty0 /dev/tty0 4 0 system:vtmaster /dev/ptmx /dev/ptmx 5 2 system /dev/console /dev/console 5 1 system:console /dev/tty /dev/tty 5 0 system:/dev/tty unknown /dev/tty 4 1-63 console 1.8 Miscellaneous kernel statistics in /proc/stat ------------------------------------------------- Various pieces of information about kernel activity are available in the /proc/stat file. All of the numbers reported in this file are aggregates since the system first booted. For a quick look, simply cat the file: > cat /proc/stat cpu 2255 34 2290 22625563 6290 127 456 0 cpu0 1132 34 1441 11311718 3675 127 438 0 cpu1 1123 0 849 11313845 2614 0 18 0 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] ctxt 1990473 btime 1062191376 processes 2915 procs_running 1 procs_blocked 0 The very first "cpu" line aggregates the numbers in all of the other "cpuN" lines. These numbers identify the amount of time the CPU has spent performing different kinds of work. Time units are in USER_HZ (typically hundredths of a second). The meanings of the columns are as follows, from left to right: - user: normal processes executing in user mode - nice: niced processes executing in user mode - system: processes executing in kernel mode - idle: twiddling thumbs - iowait: waiting for I/O to complete - irq: servicing interrupts - softirq: servicing softirqs - steal: involuntary wait The "intr" line gives counts of interrupts serviced since boot time, for each of the possible system interrupts. The first column is the total of all interrupts serviced; each subsequent column is the total for that particular interrupt. The "ctxt" line gives the total number of context switches across all CPUs. The "btime" line gives the time at which the system booted, in seconds since the Unix epoch. The "processes" line gives the number of processes and threads created, which includes (but is not limited to) those created by calls to the fork() and clone() system calls. The "procs_running" line gives the number of processes currently running on CPUs. The "procs_blocked" line gives the number of processes currently blocked, waiting for I/O to complete. 1.9 Ext4 file system parameters ------------------------------ Information about mounted ext4 file systems can be found in /proc/fs/ext4. Each mounted filesystem will have a directory in /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or /proc/fs/ext4/dm-0). The files in each per-device directory are shown in Table 1-10, below. Table 1-10: Files in /proc/fs/ext4/ .............................................................................. File Content mb_groups details of multiblock allocator buddy cache of free blocks mb_history multiblock allocation history stats controls whether the multiblock allocator should start collecting statistics, which are shown during the unmount group_prealloc the multiblock allocator will round up allocation requests to a multiple of this tuning parameter if the stripe size is not set in the ext4 superblock max_to_scan The maximum number of extents the multiblock allocator will search to find the best extent min_to_scan The minimum number of extents the multiblock allocator will search to find the best extent order2_req Tuning parameter which controls the minimum size for requests (as a power of 2) where the buddy cache is used stream_req Files which have fewer blocks than this tunable parameter will have their blocks allocated out of a block group specific preallocation pool, so that small files are packed closely together. Each large file will have its blocks allocated out of its own unique preallocation pool. inode_readahead Tuning parameter which controls the maximum number of inode table blocks that ext4's inode table readahead algorithm will pre-read into the buffer cache .............................................................................. ------------------------------------------------------------------------------ Summary ------------------------------------------------------------------------------ The /proc file system serves information about the running system. It not only allows access to process data but also allows you to request the kernel status by reading files in the hierarchy. The directory structure of /proc reflects the types of information and makes it easy, if not obvious, where to look for specific data. ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ CHAPTER 2: MODIFYING SYSTEM PARAMETERS ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ In This Chapter ------------------------------------------------------------------------------ * Modifying kernel parameters by writing into files found in /proc/sys * Exploring the files which modify certain parameters * Review of the /proc/sys file tree ------------------------------------------------------------------------------ A very interesting part of /proc is the directory /proc/sys. This is not only a source of information, it also allows you to change parameters within the kernel. Be very careful when attempting this. You can optimize your system, but you can also cause it to crash. Never alter kernel parameters on a production system. Set up a development machine and test to make sure that everything works the way you want it to. You may have no alternative but to reboot the machine once an error has been made. To change a value, simply echo the new value into the file. An example is given below in the section on the file system data. You need to be root to do this. You can create your own boot script to perform this every time your system boots. The files in /proc/sys can be used to fine tune and monitor miscellaneous and general things in the operation of the Linux kernel. Since some of the files can inadvertently disrupt your system, it is advisable to read both documentation and source before actually making adjustments. In any case, be very careful when writing to any of these files. The entries in /proc may change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt review the kernel documentation in the directory /usr/src/linux/Documentation. This chapter is heavily based on the documentation included in the pre 2.2 kernels, and became part of it in version 2.2.1 of the Linux kernel. 2.1 /proc/sys/fs - File system data ----------------------------------- This subdirectory contains specific file system, file handle, inode, dentry and quota information. Currently, these files are in /proc/sys/fs: dentry-state ------------ Status of the directory cache. Since directory entries are dynamically allocated and deallocated, this file indicates the current status. It holds six values, in which the last two are not used and are always zero. The others are listed in table 2-1. Table 2-1: Status files of the directory cache .............................................................................. File Content nr_dentry Almost always zero nr_unused Number of unused cache entries age_limit in seconds after the entry may be reclaimed, when memory is short want_pages internally .............................................................................. dquot-nr and dquot-max ---------------------- The file dquot-max shows the maximum number of cached disk quota entries. The file dquot-nr shows the number of allocated disk quota entries and the number of free disk quota entries. If the number of available cached disk quotas is very low and you have a large number of simultaneous system users, you might want to raise the limit. file-nr and file-max -------------------- The kernel allocates file handles dynamically, but doesn't free them again at this time. The value in file-max denotes the maximum number of file handles that the Linux kernel will allocate. When you get a lot of error messages about running out of file handles, you might want to raise this limit. The default value is 10% of RAM in kilobytes. To change it, just write the new number into the file: # cat /proc/sys/fs/file-max 4096 # echo 8192 > /proc/sys/fs/file-max # cat /proc/sys/fs/file-max 8192 This method of revision is useful for all customizable parameters of the kernel - simply echo the new value to the corresponding file. Historically, the three values in file-nr denoted the number of allocated file handles, the number of allocated but unused file handles, and the maximum number of file handles. Linux 2.6 always reports 0 as the number of free file handles -- this is not an error, it just means that the number of allocated file handles exactly matches the number of used file handles. Attempts to allocate more file descriptors than file-max are reported with printk, look for "VFS: file-max limit reached". inode-state and inode-nr ------------------------ The file inode-nr contains the first two items from inode-state, so we'll skip to that file... inode-state contains two actual numbers and five dummy values. The numbers are nr_inodes and nr_free_inodes (in order of appearance). nr_inodes ~~~~~~~~~ Denotes the number of inodes the system has allocated. This number will grow and shrink dynamically. nr_open ------- Denotes the maximum number of file-handles a process can allocate. Default value is 1024*1024 (1048576) which should be enough for most machines. Actual limit depends on RLIMIT_NOFILE resource limit. nr_free_inodes -------------- Represents the number of free inodes. Ie. The number of inuse inodes is (nr_inodes - nr_free_inodes). aio-nr and aio-max-nr --------------------- aio-nr is the running total of the number of events specified on the io_setup system call for all currently active aio contexts. If aio-nr reaches aio-max-nr then io_setup will fail with EAGAIN. Note that raising aio-max-nr does not result in the pre-allocation or re-sizing of any kernel data structures. 2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats ----------------------------------------------------------- Besides these files, there is the subdirectory /proc/sys/fs/binfmt_misc. This handles the kernel support for miscellaneous binary formats. Binfmt_misc provides the ability to register additional binary formats to the Kernel without compiling an additional module/kernel. Therefore, binfmt_misc needs to know magic numbers at the beginning or the filename extension of the binary. It works by maintaining a linked list of structs that contain a description of a binary format, including a magic with size (or the filename extension), offset and mask, and the interpreter name. On request it invokes the given interpreter with the original program as argument, as binfmt_java and binfmt_em86 and binfmt_mz do. Since binfmt_misc does not define any default binary-formats, you have to register an additional binary-format. There are two general files in binfmt_misc and one file per registered format. The two general files are register and status. Registering a new binary format ------------------------------- To register a new binary format you have to issue the command echo :name:type:offset:magic:mask:interpreter: > /proc/sys/fs/binfmt_misc/register with appropriate name (the name for the /proc-dir entry), offset (defaults to 0, if omitted), magic, mask (which can be omitted, defaults to all 0xff) and last but not least, the interpreter that is to be invoked (for example and testing /bin/echo). Type can be M for usual magic matching or E for filename extension matching (give extension in place of magic). Check or reset the status of the binary format handler ------------------------------------------------------ If you do a cat on the file /proc/sys/fs/binfmt_misc/status, you will get the current status (enabled/disabled) of binfmt_misc. Change the status by echoing 0 (disables) or 1 (enables) or -1 (caution: this clears all previously registered binary formats) to status. For example echo 0 > status to disable binfmt_misc (temporarily). Status of a single handler -------------------------- Each registered handler has an entry in /proc/sys/fs/binfmt_misc. These files perform the same function as status, but their scope is limited to the actual binary format. By cating this file, you also receive all related information about the interpreter/magic of the binfmt. Example usage of binfmt_misc (emulate binfmt_java) -------------------------------------------------- cd /proc/sys/fs/binfmt_misc echo ':Java:M::/xca/xfe/xba/xbe::/usr/local/java/bin/javawrapper:' > register echo ':HTML:E::html::/usr/local/java/bin/appletviewer:' > register echo ':Applet:M::