5.2. Top-level Files within the proc File System
apmcommand. If a system with no battery is connected to an AC power source, this virtual file would look similar to the following:
1.16 1.2 0x07 0x01 0xff 0x80 -1% -1 ?
apm -vcommand on such a system results in output similar to the following:
APM BIOS 1.2 (kernel driver 1.16ac) AC on-line, no system battery
apmis able do little more than put the machine in standby mode. The
apmcommand is much more useful on laptops. For example, the following output is from the command
cat /proc/apmon a laptop while plugged into a power outlet:
1.16 1.2 0x03 0x01 0x03 0x09 100% -1 ?
apmfile changes to something like the following:
1.16 1.2 0x03 0x00 0x00 0x01 99% 1792 min
apm -vcommand now yields more useful data, such as the following:
APM BIOS 1.2 (kernel driver 1.16) AC off-line, battery status high: 99% (1 day, 5:52)
DMArow references the first 16 MB on a system, the
HighMemrow references all memory greater than 4 GB on a system, and the
Normalrow references all memory in between.
Node 0, zone DMA 90 6 2 1 1 ... Node 0, zone Normal 1650 310 5 0 0 ... Node 0, zone HighMem 2 0 0 1 1 ...
/proc/cmdlinefile looks like the following:
ro root=/dev/VolGroup00/LogVol00 rhgb quiet 3
- The root device is mounted read-only at boot time. The presence of
roon the kernel boot line overrides any instances of
- This tells us on which disk device or, in this case, on which logical volume, the root filesystem image is located. With our sample
/proc/cmdlineoutput, the root filesystem image is located on the first logical volume (
LogVol00) of the first LVM volume group (
VolGroup00). On a system not using Logical Volume Management, the root file system might be located on
/dev/sda2, meaning on either the first or second partition of the first SCSI or SATA disk drive, depending on whether we have a separate (preceding) boot or swap partition on that drive.For more information on LVM used in Red Hat Enterprise Linux, refer to http://www.tldp.org/HOWTO/LVM-HOWTO/index.html.
- A short lowercase acronym that stands for Red Hat Graphical Boot, providing "rhgb" on the kernel command line signals that graphical booting is supported, assuming that
/etc/inittabshows that the default runlevel is set to 5 with a line like this:
- Indicates that all verbose kernel messages except those which are extremely serious should be suppressed at boot time.
processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) Xeon(TM) CPU 2.40GHz stepping : 7 cpu MHz : 2392.371 cache size : 512 KB physical id : 0 siblings : 2 runqueue : 0 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 4771.02
processor— Provides each processor with an identifying number. On systems that have one processor, only a
cpu family— Authoritatively identifies the type of processor in the system. For an Intel-based system, place the number in front of "86" to determine the value. This is particularly helpful for those attempting to identify the architecture of an older system such as a 586, 486, or 386. Because some RPM packages are compiled for each of these particular architectures, this value also helps users determine which packages to install.
model name— Displays the common name of the processor, including its project name.
cpu MHz— Shows the precise speed in megahertz for the processor to the thousandths decimal place.
cache size— Displays the amount of level 2 memory cache available to the processor.
siblings— Displays the number of sibling CPUs on the same physical CPU for architectures which use hyper-threading.
flags— Defines a number of different qualities about the processor, such as the presence of a floating point unit (FPU) and the ability to process MMX instructions.
/proc/cryptofile looks like the following:
name : sha1 module : kernel type : digest blocksize : 64 digestsize : 20 name : md5 module : md5 type : digest blocksize : 64 digestsize : 16
Character devices: 1 mem 4 /dev/vc/0 4 tty 4 ttyS 5 /dev/tty 5 /dev/console 5 /dev/ptmx 7 vcs 10 misc 13 input 29 fb 36 netlink 128 ptm 136 pts 180 usb Block devices: 1 ramdisk 3 ide0 9 md 22 ide1 253 device-mapper 254 mdp
/proc/devicesincludes the major number and name of the device, and is broken into two major sections:
- Character devices do not require buffering. Block devices have a buffer available, allowing them to order requests before addressing them. This is important for devices designed to store information — such as hard drives — because the ability to order the information before writing it to the device allows it to be placed in a more efficient order.
- Character devices send data with no preconfigured size. Block devices can send and receive information in blocks of a size configured per device.
/proc/dmafiles looks like the following:
0-0 Linux [kernel]
PER_LINUXexecution domain, different personalities can be implemented as dynamically loadable modules.
/proc/fbfor systems which contain frame buffer devices looks similar to the following:
0 VESA VGA
/proc/filesystemsfile looks similar to the following:
nodev sysfs nodev rootfs nodev bdev nodev proc nodev sockfs nodev binfmt_misc nodev usbfs nodev usbdevfs nodev futexfs nodev tmpfs nodev pipefs nodev eventpollfs nodev devpts ext2 nodev ramfs nodev hugetlbfs iso9660 nodev mqueue ext3 nodev rpc_pipefs nodev autofs
nodevare not mounted on a device. The second column lists the names of the file systems supported.
mountcommand cycles through the file systems listed here when one is not specified as an argument.
/proc/interruptslooks similar to the following:
CPU0 0: 80448940 XT-PIC timer 1: 174412 XT-PIC keyboard 2: 0 XT-PIC cascade 8: 1 XT-PIC rtc 10: 410964 XT-PIC eth0 12: 60330 XT-PIC PS/2 Mouse 14: 1314121 XT-PIC ide0 15: 5195422 XT-PIC ide1 NMI: 0 ERR: 0
CPU0 CPU1 0: 1366814704 0 XT-PIC timer 1: 128 340 IO-APIC-edge keyboard 2: 0 0 XT-PIC cascade 8: 0 1 IO-APIC-edge rtc 12: 5323 5793 IO-APIC-edge PS/2 Mouse 13: 1 0 XT-PIC fpu 16: 11184294 15940594 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet 20: 8450043 11120093 IO-APIC-level megaraid 30: 10432 10722 IO-APIC-level aic7xxx 31: 23 22 IO-APIC-level aic7xxx NMI: 0 ERR: 0
XT-PIC— This is the old AT computer interrupts.
IO-APIC-edge— The voltage signal on this interrupt transitions from low to high, creating an edge, where the interrupt occurs and is only signaled once. This kind of interrupt, as well as the
IO-APIC-levelinterrupt, are only seen on systems with processors from the 586 family and higher.
IO-APIC-level— Generates interrupts when its voltage signal is high until the signal is low again.
00000000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000a0000-000bffff : Video RAM area 000c0000-000c7fff : Video ROM 000f0000-000fffff : System ROM 00100000-07ffffff : System RAM 00100000-00291ba8 : Kernel code 00291ba9-002e09cb : Kernel data e0000000-e3ffffff : VIA Technologies, Inc. VT82C597 [Apollo VP3] e4000000-e7ffffff : PCI Bus #01 e4000000-e4003fff : Matrox Graphics, Inc. MGA G200 AGP e5000000-e57fffff : Matrox Graphics, Inc. MGA G200 AGP e8000000-e8ffffff : PCI Bus #01 e8000000-e8ffffff : Matrox Graphics, Inc. MGA G200 AGP ea000000-ea00007f : Digital Equipment Corporation DECchip 21140 [FasterNet] ea000000-ea00007f : tulip ffff0000-ffffffff : reserved
/proc/ioportsprovides a list of currently registered port regions used for input or output communication with a device. This file can be quite long. The following is a partial listing:
0000-001f : dma1 0020-003f : pic1 0040-005f : timer 0060-006f : keyboard 0070-007f : rtc 0080-008f : dma page reg 00a0-00bf : pic2 00c0-00df : dma2 00f0-00ff : fpu 0170-0177 : ide1 01f0-01f7 : ide0 02f8-02ff : serial(auto) 0376-0376 : ide1 03c0-03df : vga+ 03f6-03f6 : ide0 03f8-03ff : serial(auto) 0cf8-0cff : PCI conf1 d000-dfff : PCI Bus #01 e000-e00f : VIA Technologies, Inc. Bus Master IDE e000-e007 : ide0 e008-e00f : ide1 e800-e87f : Digital Equipment Corporation DECchip 21140 [FasterNet] e800-e87f : tulip
kcoredisplays a size. This value is given in bytes and is equal to the size of the physical memory (RAM) used plus 4 KB.
gdb, and is not human readable.
/proc/kcorevirtual file. The contents of the file scramble text output on the terminal. If this file is accidentally viewed, press Ctrl+C to stop the process and then type
resetto bring back the command line prompt.
uptimeand other commands. A sample
/proc/loadavgfile looks similar to the following:
0.20 0.18 0.12 1/80 11206
/proc/locksfile for a lightly loaded system looks similar to the following:
1: POSIX ADVISORY WRITE 3568 fd:00:2531452 0 EOF 2: FLOCK ADVISORY WRITE 3517 fd:00:2531448 0 EOF 3: POSIX ADVISORY WRITE 3452 fd:00:2531442 0 EOF 4: POSIX ADVISORY WRITE 3443 fd:00:2531440 0 EOF 5: POSIX ADVISORY WRITE 3326 fd:00:2531430 0 EOF 6: POSIX ADVISORY WRITE 3175 fd:00:2531425 0 EOF 7: POSIX ADVISORY WRITE 3056 fd:00:2548663 0 EOF
FLOCKsignifying the older-style UNIX file locks from a
flocksystem call and
POSIXrepresenting the newer POSIX locks from the
ADVISORYmeans that the lock does not prevent other people from accessing the data; it only prevents other attempts to lock it.
MANDATORYmeans that no other access to the data is permitted while the lock is held. The fourth column reveals whether the lock is allowing the holder
WRITEaccess to the file. The fifth column shows the ID of the process holding the lock. The sixth column shows the ID of the file being locked, in the format of
MAJOR-DEVICE:MINOR-DEVICE:INODE-NUMBER. The seventh and eighth column shows the start and end of the file's locked region.
/proc/mdstatlooks similar to the following:
Personalities : read_ahead not set unused devices: <none>
mddevice is present. In that case, view
/proc/mdstatto find the current status of
/proc/mdstatfile below shows a system with its
md0configured as a RAID 1 device, while it is currently re-syncing the disks:
Personalities : [linear] [raid1] read_ahead 1024 sectors md0: active raid1 sda2 sdb2 9940 blocks [2/2] [UU] resync=1% finish=12.3min algorithm 2 [3/3] [UUU] unused devices: <none>
/proc/directory, as it reports a large amount of valuable information about the systems RAM usage.
/proc/meminfovirtual file is from a system with 256 MB of RAM and 512 MB of swap space:
MemTotal: 255908 kB MemFree: 69936 kB Buffers: 15812 kB Cached: 115124 kB SwapCached: 0 kB Active: 92700 kB Inactive: 63792 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 255908 kB LowFree: 69936 kB SwapTotal: 524280 kB SwapFree: 524280 kB Dirty: 4 kB Writeback: 0 kB Mapped: 42236 kB Slab: 25912 kB Committed_AS: 118680 kB PageTables: 1236 kB VmallocTotal: 3874808 kB VmallocUsed: 1416 kB VmallocChunk: 3872908 kB HugePages_Total: 0 HugePages_Free: 0 Hugepagesize: 4096 kB
pscommands. In fact, the output of the
freecommand is similar in appearance to the contents and structure of
/proc/meminfo. But by looking directly at
/proc/meminfo, more details are revealed:
MemTotal— Total amount of physical RAM, in kilobytes.
MemFree— The amount of physical RAM, in kilobytes, left unused by the system.
Buffers— The amount of physical RAM, in kilobytes, used for file buffers.
Cached— The amount of physical RAM, in kilobytes, used as cache memory.
SwapCached— The amount of swap, in kilobytes, used as cache memory.
Active— The total amount of buffer or page cache memory, in kilobytes, that is in active use. This is memory that has been recently used and is usually not reclaimed for other purposes.
Inactive— The total amount of buffer or page cache memory, in kilobytes, that are free and available. This is memory that has not been recently used and can be reclaimed for other purposes.
HighFree— The total and free amount of memory, in kilobytes, that is not directly mapped into kernel space. The
HighTotalvalue can vary based on the type of kernel used.
LowFree— The total and free amount of memory, in kilobytes, that is directly mapped into kernel space. The
LowTotalvalue can vary based on the type of kernel used.
SwapTotal— The total amount of swap available, in kilobytes.
SwapFree— The total amount of swap free, in kilobytes.
Dirty— The total amount of memory, in kilobytes, waiting to be written back to the disk.
Writeback— The total amount of memory, in kilobytes, actively being written back to the disk.
Mapped— The total amount of memory, in kilobytes, which have been used to map devices, files, or libraries using the
Slab— The total amount of memory, in kilobytes, used by the kernel to cache data structures for its own use.
Committed_AS— The total amount of memory, in kilobytes, estimated to complete the workload. This value represents the worst case scenario value, and also includes swap memory.
PageTables— The total amount of memory, in kilobytes, dedicated to the lowest page table level.
VMallocTotal— The total amount of memory, in kilobytes, of total allocated virtual address space.
VMallocUsed— The total amount of memory, in kilobytes, of used virtual address space.
VMallocChunk— The largest contiguous block of memory, in kilobytes, of available virtual address space.
HugePages_Total— The total number of hugepages for the system. The number is derived by dividing
Hugepagesizeby the megabytes set aside for hugepages specified in
/proc/sys/vm/hugetlb_pool. This statistic only appears on the x86, Itanium, and AMD64 architectures.
HugePages_Free— The total number of hugepages available for the system. This statistic only appears on the x86, Itanium, and AMD64 architectures.
Hugepagesize— The size for each hugepages unit in kilobytes. By default, the value is 4096 KB on uniprocessor kernels for 32 bit architectures. For SMP, hugemem kernels, and AMD64, the default is 2048 KB. For Itanium architectures, the default is 262144 KB. This statistic only appears on the x86, Itanium, and AMD64 architectures.
63 device-mapper 175 agpgart 135 rtc 134 apm_bios
nfs 170109 0 - Live 0x129b0000 lockd 51593 1 nfs, Live 0x128b0000 nls_utf8 1729 0 - Live 0x12830000 vfat 12097 0 - Live 0x12823000 fat 38881 1 vfat, Live 0x1287b000 autofs4 20293 2 - Live 0x1284f000 sunrpc 140453 3 nfs,lockd, Live 0x12954000 3c59x 33257 0 - Live 0x12871000 uhci_hcd 28377 0 - Live 0x12869000 md5 3777 1 - Live 0x1282c000 ipv6 211845 16 - Live 0x128de000 ext3 92585 2 - Live 0x12886000 jbd 65625 1 ext3, Live 0x12857000 dm_mod 46677 3 - Live 0x12833000
Unloadingare the only possible values.
rootfs / rootfs rw 0 0 /proc /proc proc rw,nodiratime 0 0 none /dev ramfs rw 0 0 /dev/mapper/VolGroup00-LogVol00 / ext3 rw 0 0 none /dev ramfs rw 0 0 /proc /proc proc rw,nodiratime 0 0 /sys /sys sysfs rw 0 0 none /dev/pts devpts rw 0 0 usbdevfs /proc/bus/usb usbdevfs rw 0 0 /dev/hda1 /boot ext3 rw 0 0 none /dev/shm tmpfs rw 0 0 none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0 sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0
/etc/mtab, except that
/proc/mountis more up-to-date.
ro) or read-write (
rw). The fifth and sixth columns are dummy values designed to match the format used in
/proc/mtrrfile may look similar to the following:
reg00: base=0x00000000 ( 0MB), size= 256MB: write-back, count=1 reg01: base=0xe8000000 (3712MB), size= 32MB: write-combining, count=1
/proc/mtrrfile can increase performance more than 150%.
major minor #blocks name 3 0 19531250 hda 3 1 104391 hda1 3 2 19422585 hda2 253 0 22708224 dm-0 253 1 524288 dm-1
major— The major number of the device with this partition. The major number in the
3), corresponds with the block device
minor— The minor number of the device with this partition. This serves to separate the partitions into different physical devices and relates to the number at the end of the name of the partition.
#blocks— Lists the number of physical disk blocks contained in a particular partition.
name— The name of the partition.
/proc/pcican be rather long. A sampling of this file from a basic system looks similar to the following:
Bus 0, device 0, function 0: Host bridge: Intel Corporation 440BX/ZX - 82443BX/ZX Host bridge (rev 3). Master Capable. Latency=64. Prefetchable 32 bit memory at 0xe4000000 [0xe7ffffff]. Bus 0, device 1, function 0: PCI bridge: Intel Corporation 440BX/ZX - 82443BX/ZX AGP bridge (rev 3). Master Capable. Latency=64. Min Gnt=128. Bus 0, device 4, function 0: ISA bridge: Intel Corporation 82371AB PIIX4 ISA (rev 2). Bus 0, device 4, function 1: IDE interface: Intel Corporation 82371AB PIIX4 IDE (rev 1). Master Capable. Latency=32. I/O at 0xd800 [0xd80f]. Bus 0, device 4, function 2: USB Controller: Intel Corporation 82371AB PIIX4 USB (rev 1). IRQ 5. Master Capable. Latency=32. I/O at 0xd400 [0xd41f]. Bus 0, device 4, function 3: Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 2). IRQ 9. Bus 0, device 9, function 0: Ethernet controller: Lite-On Communications Inc LNE100TX (rev 33). IRQ 5. Master Capable. Latency=32. I/O at 0xd000 [0xd0ff]. Bus 0, device 12, function 0: VGA compatible controller: S3 Inc. ViRGE/DX or /GX (rev 1). IRQ 11. Master Capable. Latency=32. Min Gnt=4.Max Lat=255.
/proc/slabinfofile manually, the
/usr/bin/slabtopprogram displays kernel slab cache information in real time. This program allows for custom configurations, including column sorting and screen refreshing.
/usr/bin/slabtopusually looks like the following example:
Active / Total Objects (% used) : 133629 / 147300 (90.7%) Active / Total Slabs (% used) : 11492 / 11493 (100.0%) Active / Total Caches (% used) : 77 / 121 (63.6%) Active / Total Size (% used) : 41739.83K / 44081.89K (94.7%) Minimum / Average / Maximum Object : 0.01K / 0.30K / 128.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 44814 43159 96% 0.62K 7469 6 29876K ext3_inode_cache 36900 34614 93% 0.05K 492 75 1968K buffer_head 35213 33124 94% 0.16K 1531 23 6124K dentry_cache 7364 6463 87% 0.27K 526 14 2104K radix_tree_node 2585 1781 68% 0.08K 55 47 220K vm_area_struct 2263 2116 93% 0.12K 73 31 292K size-128 1904 1125 59% 0.03K 16 119 64K size-32 1666 768 46% 0.03K 14 119 56K anon_vma 1512 1482 98% 0.44K 168 9 672K inode_cache 1464 1040 71% 0.06K 24 61 96K size-64 1320 820 62% 0.19K 66 20 264K filp 678 587 86% 0.02K 3 226 12K dm_io 678 587 86% 0.02K 3 226 12K dm_tio 576 574 99% 0.47K 72 8 288K proc_inode_cache 528 514 97% 0.50K 66 8 264K size-512 492 372 75% 0.09K 12 41 48K bio 465 314 67% 0.25K 31 15 124K size-256 452 331 73% 0.02K 2 226 8K biovec-1 420 420 100% 0.19K 21 20 84K skbuff_head_cache 305 256 83% 0.06K 5 61 20K biovec-4 290 4 1% 0.01K 1 290 4K revoke_table 264 264 100% 4.00K 264 1 1056K size-4096 260 256 98% 0.19K 13 20 52K biovec-16 260 256 98% 0.75K 52 5 208K biovec-64
/proc/slabinfothat are included into
OBJS— The total number of objects (memory blocks), including those in use (allocated), and some spares not in use.
ACTIVE— The number of objects (memory blocks) that are in use (allocated).
USE— Percentage of total objects that are active. ((ACTIVE/OBJS)(100))
OBJ SIZE— The size of the objects.
SLABS— The total number of slabs.
OBJ/SLAB— The number of objects that fit into a slab.
CACHE SIZE— The cache size of the slab.
NAME— The name of the slab.
/usr/bin/slabtopprogram, refer to the
/proc/stat, which can be quite long, usually begins like the following example:
cpu 259246 7001 60190 34250993 137517 772 0 cpu0 259246 7001 60190 34250993 137517 772 0 intr 354133732 347209999 2272 0 4 4 0 0 3 1 1249247 0 0 80143 0 422626 5169433 ctxt 12547729 btime 1093631447 processes 130523 procs_running 1 procs_blocked 0 preempt 5651840 cpu 209841 1554 21720 118519346 72939 154 27168 cpu0 42536 798 4841 14790880 14778 124 3117 cpu1 24184 569 3875 14794524 30209 29 3130 cpu2 28616 11 2182 14818198 4020 1 3493 cpu3 35350 6 2942 14811519 3045 0 3659 cpu4 18209 135 2263 14820076 12465 0 3373 cpu5 20795 35 1866 14825701 4508 0 3615 cpu6 21607 0 2201 14827053 2325 0 3334 cpu7 18544 0 1550 14831395 1589 0 3447 intr 15239682 14857833 6 0 6 6 0 5 0 1 0 0 0 29 0 2 0 0 0 0 0 0 0 94982 0 286812 ctxt 4209609 btime 1078711415 processes 21905 procs_running 1 procs_blocked 0
cpu— Measures the number of jiffies (1/100 of a second for x86 systems) that the system has been in user mode, user mode with low priority (nice), system mode, idle task, I/O wait, IRQ (hardirq), and softirq respectively. The IRQ (hardirq) is the direct response to a hardware event. The IRQ takes minimal work for queuing the "heavy" work up for the softirq to execute. The softirq runs at a lower priority than the IRQ and therefore may be interrupted more frequently. The total for all CPUs is given at the top, while each individual CPU is listed below with its own statistics. The following example is a 4-way Intel Pentium Xeon configuration with multi-threading enabled, therefore showing four physical processors and four virtual processors totaling eight processors.
page— The number of memory pages the system has written in and out to disk.
swap— The number of swap pages the system has brought in and out.
intr— The number of interrupts the system has experienced.
btime— The boot time, measured in the number of seconds since January 1, 1970, otherwise known as the epoch.
/proc/swapsmay look similar to the following:
Filename Type Size Used Priority /dev/mapper/VolGroup00-LogVol01 partition 524280 0 -1
/proc/swapsprovides a snapshot of every swap file name, the type of swap space, the total size, and the amount of space in use (in kilobytes). The priority column is useful when multiple swap files are in use. The lower the priority, the more likely the swap file is to be used.
echocommand to write to this file, a remote root user can execute most System Request Key commands remotely as if at the local terminal. To
echovalues to this file, the
/proc/sys/kernel/sysrqmust be set to a value other than
0. For more information about the System Request Key, refer to Section 188.8.131.52, “
/proc/uptimeis quite minimal:
gccin use, as well as the version of Red Hat Enterprise Linux installed on the system:
Linux version 2.6.8-1.523 (firstname.lastname@example.org) (gcc version 3.4.1 20040714 \ (Red Hat Enterprise Linux 3.4.1-7)) #1 Mon Aug 16 13:27:03 EDT 2004